Chapter 34 — Anti-Cancer Drugs Part 2 — Module 3 — Monoclonal Antibodies and Antibody-Drug Conjugates
1. [CASE 1 — QUESTION 1]
A 49-year-old woman with newly diagnosed HER2-positive (human epidermal growth factor receptor 2-positive) early breast cancer has a baseline left ventricular ejection fraction (LVEF, the percentage of blood ejected from the left ventricle per beat) of 62 percent and normal cardiac history. Her oncologist plans an anthracycline-based regimen (doxorubicin-cyclophosphamide) followed by a HER2-directed antibody, with the goal of curative-intent adjuvant therapy. The treatment team is deciding how to combine the anthracycline and trastuzumab. Which approach to combining these agents is correct?
A) Administer doxorubicin and trastuzumab concurrently in every cycle to maximize synergistic tumor kill
B) Give trastuzumab first to saturate HER2 receptors, then add doxorubicin in the same cycle
C) Complete the anthracycline-based chemotherapy first and begin trastuzumab only after the last anthracycline dose, because concurrent administration produces unacceptably high rates of symptomatic heart failure whereas sequential use reduces symptomatic cardiac events substantially
D) Alternate doxorubicin and trastuzumab on the same treatment day to balance their cardiac effects
E) Omit the anthracycline entirely, since prior anthracycline exposure is an absolute contraindication to trastuzumab
ANSWER: C
Rationale:
Concurrent administration of trastuzumab with an anthracycline is contraindicated because it produced unacceptably high rates of symptomatic heart failure (approximately 27 percent in the pivotal HER2 trial). The standard is sequential therapy: complete the anthracycline-based chemotherapy first, then start trastuzumab after the final anthracycline dose, which lowers symptomatic cardiac events to roughly 2 to 4 percent.
Option A: Option A is incorrect because concurrent administration is precisely what generates the prohibitive cardiotoxicity.
Option B: Option B is incorrect because giving trastuzumab first to "saturate" receptors does not address the additive cardiac injury of same-cycle co-administration.
Option D: Option D is incorrect because alternating the drugs on the same day is still concurrent exposure and does not mitigate the additive cardiotoxicity.
Option E: Option E is incorrect because prior anthracycline exposure is not an absolute contraindication to trastuzumab; sequential use after completing anthracycline therapy is standard.
2. [CASE 1 — QUESTION 2]
Continuing with the same patient. She completes anthracycline-based chemotherapy and begins trastuzumab. At a routine surveillance assessment several months into trastuzumab, she is asymptomatic but her LVEF has fallen from 62 percent to 45 percent. This is her first qualifying decline. What is the most appropriate management of her trastuzumab?
A) Hold trastuzumab and reassess LVEF after an interval (typically 4 to 8 weeks); because trastuzumab cardiotoxicity reflects reversible blockade of HER2/HER4 cardiac repair signaling, reinitiation is appropriate in most cases after recovery, with permanent discontinuation reserved for persistent decline after hold-and-reassess cycles
B) Permanently discontinue trastuzumab immediately on this first qualifying measurement, since the decline is irreversible
C) Continue trastuzumab at full dose, since asymptomatic LVEF changes never warrant intervention
D) Resume the anthracycline to counteract the HER2-related cardiac effect
E) Increase the trastuzumab dose to overcome apparent tumor resistance signaled by the LVEF drop
ANSWER: A
Rationale:
Trastuzumab is held for an LVEF below 50 percent or a decline of 16 or more percentage points; her LVEF of 45 percent (a 17-point drop) meets both. Because trastuzumab cardiotoxicity is largely reversible, the standard response is to hold and reassess after roughly 4 to 8 weeks, reinitiating in most cases after recovery, with permanent discontinuation reserved for persistent decline after hold-and-reassess cycles.
Option B: Option B is incorrect because the first qualifying decline triggers hold and reassessment, not immediate permanent discontinuation, and the toxicity is usually reversible.
Option C: Option C is incorrect because this LVEF clearly meets the hold threshold and requires action.
Option D: Option D is incorrect because resuming an anthracycline would compound, not counteract, cardiac injury.
Option E: Option E is incorrect because the LVEF decline reflects cardiotoxicity, not tumor resistance, and dose escalation would worsen it.
3. [CASE 1 — QUESTION 3]
Continuing with the same patient. Consider instead an alternative course in which she had received neoadjuvant (pre-surgical) HER2-directed chemotherapy and then underwent surgery, with the pathology showing residual invasive disease in the breast. Her LVEF has recovered to 58 percent. A pivotal adjuvant trial defined the standard of care for HER2-positive patients with residual disease after neoadjuvant therapy. Which agent does that trial support for her in this setting?
A) Continue plain trastuzumab alone, since residual disease does not change adjuvant antibody selection
B) Switch to bevacizumab, an anti-VEGF antibody, for residual HER2-positive disease
C) Add cetuximab, an anti-EGFR antibody, to standard trastuzumab
D) Trastuzumab emtansine (T-DM1), an antibody-drug conjugate that links trastuzumab to a cytotoxic emtansine payload, which is the established adjuvant standard for HER2-positive early breast cancer with residual disease after neoadjuvant chemotherapy and is a distinct drug from trastuzumab
E) Pertuzumab monotherapy without any cytotoxic component
ANSWER: D
Rationale:
For HER2-positive early breast cancer with residual invasive disease after neoadjuvant chemotherapy, the pivotal adjuvant trial established trastuzumab emtansine (T-DM1) as standard of care. T-DM1 links trastuzumab to a cytotoxic emtansine payload and is a distinct drug from trastuzumab, delivering the payload preferentially to HER2-expressing cells.
Option A: Option A is incorrect because residual disease after neoadjuvant therapy specifically changes management toward T-DM1 rather than continued trastuzumab alone.
Option B: Option B is incorrect because bevacizumab targets VEGF and is not the adjuvant standard for residual HER2-positive disease.
Option C: Option C is incorrect because cetuximab targets EGFR and has no role in breast cancer.
Option E: Option E is incorrect because pertuzumab is used in combination for HER2-positive disease, not as residual-disease monotherapy without a cytotoxic component.
4. [CASE 1 — QUESTION 4]
Continuing with the same patient. She begins trastuzumab emtansine (T-DM1). Before the next cycle, routine laboratory testing is planned to monitor for the characteristic dose-limiting hematologic toxicity of this antibody-drug conjugate. Which toxicity should be specifically monitored, and what is its mechanism?
A) Macrocytic anemia from emtansine-induced folate antagonism
B) Thrombocytopenia, because the emtansine (DM1) payload disrupts the microtubule dynamics required for proplatelet formation in megakaryocytes; platelet counts are monitored before each cycle, along with liver function for hepatotoxicity
C) Neutropenic fever from a topoisomerase inhibitor payload
D) Hemolytic anemia from antibody binding to red cell antigens
E) Polycythemia from erythropoietin stimulation
ANSWER: B
Rationale:
The characteristic dose-limiting hematologic toxicity of T-DM1 is thrombocytopenia, occurring because the emtansine (DM1) microtubule-inhibitor payload disrupts the microtubule dynamics required for proplatelet formation in megakaryocytes; platelet counts are monitored before each cycle, and hepatotoxicity is monitored with liver function tests.
Option A: Option A is incorrect because emtansine is a microtubule inhibitor, not a folate antagonist, and the signature toxicity is thrombocytopenia, not macrocytic anemia.
Option C: Option C is incorrect because the T-DM1 payload is a microtubule inhibitor, not a topoisomerase inhibitor, and the dominant hematologic toxicity is thrombocytopenia.
Option D: Option D is incorrect because T-DM1 does not characteristically cause hemolytic anemia through red cell antigen binding.
Option E: Option E is incorrect because T-DM1 does not stimulate erythropoietin or cause polycythemia.
5. [CASE 2 — QUESTION 1]
A 58-year-old man presents with metastatic colorectal cancer. His oncologist is considering adding cetuximab (an anti-EGFR [epidermal growth factor receptor] antibody) to chemotherapy and is reviewing the companion diagnostic and tumor-location data that govern anti-EGFR selection. Before prescribing cetuximab, which combination of findings should be confirmed to predict benefit?
A) HER2 (human epidermal growth factor receptor 2) amplification and a right-sided primary tumor
B) Wild-type RAS (rat sarcoma proto-oncogene; both KRAS and NRAS, exons 2, 3, and 4) and BRAF (v-raf murine sarcoma viral oncogene homolog B) wild-type status, together with a left-sided primary tumor, because RAS or BRAF mutations and right-sided location predict lack of benefit from anti-EGFR therapy
C) Any activating RAS mutation, which enhances anti-EGFR benefit
D) High microsatellite instability, which is the gating biomarker for anti-EGFR antibodies
E) Programmed death-ligand 1 positivity and a right-sided tumor
ANSWER: B
Rationale:
Anti-EGFR benefit requires wild-type RAS (KRAS and NRAS, exons 2, 3, and 4) and wild-type BRAF for single-agent activity, and left-sided primary tumors derive substantially more benefit than right-sided tumors. Confirming wild-type RAS and BRAF plus a left-sided primary predicts benefit.
Option A: Option A is incorrect because HER2 amplification gates HER2-directed therapy, not anti-EGFR therapy, and right-sided location predicts poor anti-EGFR benefit.
Option C: Option C is incorrect because a RAS mutation predicts lack of benefit, not enhancement.
Option D: Option D is incorrect because microsatellite instability gates immune checkpoint inhibitors, not anti-EGFR antibodies.
Option E: Option E is incorrect because programmed death-ligand 1 status guides checkpoint inhibitors, and a right-sided tumor predicts poor anti-EGFR benefit.
6. [CASE 2 — QUESTION 2]
Continuing with the same patient. His tumor is confirmed RAS and BRAF wild-type with a left-sided primary, and cetuximab is started. Two weeks later he develops a papulopustular (acneiform) rash over the face and upper trunk. He is distressed and asks whether the drug is failing. Which interpretation and management is correct?
A) The rash signals treatment failure and cetuximab should be stopped immediately
B) The rash indicates an allergic contraindication and mandates permanent discontinuation
C) The rash reflects bacterial superinfection requiring intravenous antibiotics and drug cessation
D) The rash is unrelated to cetuximab and warrants only topical emollients with no further consideration
E) The acneiform rash is an expected on-target effect of EGFR blockade whose severity correlates positively with response and survival; it is managed with prophylactic or therapeutic oral tetracyclines such as doxycycline rather than by discontinuing the drug
ANSWER: E
Rationale:
Acneiform rash occurs in about 80 percent of patients on anti-EGFR antibodies and is an on-target effect of EGFR blockade; its severity correlates positively with response and survival. It is managed with prophylactic or therapeutic oral tetracyclines such as doxycycline or minocycline, not by stopping the drug.
Option A: Option A is incorrect because the rash signals on-target activity, not failure.
Option B: Option B is incorrect because the rash is an expected pharmacologic effect, not an allergic contraindication requiring permanent discontinuation.
Option C: Option C is incorrect because the rash is not primarily a bacterial superinfection requiring intravenous antibiotics and drug cessation.
Option D: Option D is incorrect because the rash is directly related to EGFR blockade and is managed with oral tetracyclines, not dismissed.
7. [CASE 2 — QUESTION 3]
Continuing with the same patient. Several cycles into cetuximab, routine labs show a serum magnesium of 1.1 mg/dL (low), and he reports muscle cramping. Which mechanism explains this finding, and what is the appropriate response?
A) EGFR (epidermal growth factor receptor) blockade reduces expression of the TRPM6 (transient receptor potential melastatin 6) magnesium channel in the distal convoluted tubule, impairing active renal magnesium reabsorption and causing renal magnesium wasting; serum magnesium should be monitored before each cycle and repleted, as deficiency can cause neuromuscular irritability and arrhythmias
B) Cetuximab chelates magnesium in the bloodstream, and the treatment is to stop all magnesium intake
C) The hypomagnesemia is from gastrointestinal malabsorption due to mucositis and resolves without monitoring
D) EGFR blockade increases renal magnesium reabsorption, so the low value is a laboratory artifact requiring no action
E) The finding reflects parathyroid hormone suppression and is corrected with calcium alone
ANSWER: A
Rationale:
Anti-EGFR antibodies cause renal magnesium wasting because EGFR signaling normally maintains expression of the TRPM6 channel that mediates active magnesium reabsorption in the distal convoluted tubule; EGFR blockade downregulates TRPM6, impairing reabsorption. Serum magnesium should be monitored before each cycle and repleted, since deficiency can cause neuromuscular irritability and cardiac arrhythmias.
Option B: Option B is incorrect because cetuximab does not chelate plasma magnesium, and stopping magnesium intake would worsen deficiency.
Option C: Option C is incorrect because the dominant mechanism is renal wasting, not gastrointestinal malabsorption, and monitoring is required.
Option D: Option D is incorrect because EGFR blockade reduces, not increases, renal magnesium reabsorption, and the low value is real.
Option E: Option E is incorrect because the mechanism is renal magnesium wasting, not parathyroid hormone suppression, and repletion is with magnesium.
8. [CASE 2 — QUESTION 4]
Continuing with the same patient. He lives in the rural southeastern United States and has a history of tick bites. During a subsequent cetuximab infusion he develops urticaria, bronchospasm, and hypotension consistent with a severe immunoglobulin E-mediated hypersensitivity reaction. After stabilization, the team wishes to continue anti-EGFR (epidermal growth factor receptor) therapy if possible. Which explanation and option is most appropriate?
A) The reaction is a cytokine-release reaction that will not recur, so cetuximab can simply be resumed at a slower rate
B) The reaction proves anti-EGFR therapy is permanently contraindicated for him with any available agent
C) The reaction reflects pre-existing immunoglobulin E against the galactose-alpha-1,3-galactose (alpha-gal) epitope on cetuximab, which is derived from its murine cell line and is associated with tick-bite sensitization; switching to panitumumab, a fully human anti-EGFR antibody produced in a non-murine cell line that lacks the alpha-gal epitope, is a reasonable option with a substantially lower severe infusion reaction rate
D) The reaction indicates a RAS mutation has emerged and anti-EGFR therapy is now futile
E) The reaction is unrelated to the antibody and reflects an unrelated food allergy requiring no change in oncology therapy
ANSWER: C
Rationale:
Severe cetuximab infusion reactions in tick-exposed patients in the southeastern United States are frequently true immunoglobulin E-mediated reactions against the galactose-alpha-1,3-galactose (alpha-gal) epitope present on cetuximab from its murine cell-line production. Panitumumab is a fully human antibody produced in a non-murine cell line that lacks the alpha-gal epitope and has a substantially lower severe infusion reaction rate, making it a reasonable alternative.
Option A: Option A is incorrect because this is an immunoglobulin E-mediated reaction likely to recur, not a benign cytokine-release reaction.
Option B: Option B is incorrect because an alternative anti-EGFR antibody lacking the alpha-gal epitope exists, so therapy is not permanently precluded.
Option D: Option D is incorrect because the hypersensitivity reaction does not indicate emergence of a RAS mutation.
Option E: Option E is incorrect because the reaction is mechanistically tied to the cetuximab alpha-gal epitope and does warrant a change in agent.
9. [CASE 3 — QUESTION 1]
A 56-year-old man with diffuse large B-cell lymphoma is scheduled to begin a rituximab (anti-CD20 [a B-cell surface antigen])-containing regimen. Pre-treatment serologies return hepatitis B surface antigen positive with detectable hepatitis B virus DNA, indicating chronic hepatitis B infection. What is the most appropriate management before starting rituximab?
A) Proceed with rituximab without antiviral therapy because chemotherapy clears the virus
B) Cancel rituximab permanently, since chronic hepatitis B is an absolute lifelong contraindication
C) Begin antiviral therapy only if transaminases rise during treatment
D) Initiate prophylactic antiviral therapy (entecavir or tenofovir, preferred over lamivudine because of lower resistance rates) before starting rituximab and continue it for at least 12 to 18 months after completion, because rituximab-mediated B-cell depletion can drive hepatitis B reactivation with risk of fulminant hepatic failure
E) Administer hepatitis B vaccine during rituximab therapy as the primary preventive measure
ANSWER: D
Rationale:
A surface-antigen-positive patient with detectable hepatitis B virus DNA has chronic infection and is at high risk for reactivation during B-cell-depleting therapy, which can cause fulminant hepatic failure. Prophylactic antiviral therapy with entecavir or tenofovir (preferred over lamivudine for lower resistance) should begin before rituximab and continue for at least 12 to 18 months after completion.
Option A: Option A is incorrect because chemotherapy does not clear hepatitis B, and reactivation risk is high without prophylaxis.
Option B: Option B is incorrect because chronic hepatitis B is managed with antiviral prophylaxis, not permanent cancellation of needed lymphoma therapy.
Option C: Option C is incorrect because waiting for transaminase elevation means waiting for established reactivation; prophylaxis must start up front.
Option E: Option E is incorrect because B-cell depletion abolishes vaccine responses, so vaccination during therapy is not the preventive measure; antiviral prophylaxis is.
10. [CASE 3 — QUESTION 2]
Continuing with the same patient. With antiviral prophylaxis arranged, the team turns to immunizations before starting rituximab. He is due for several vaccinations. Which approach to vaccination is correct in this setting?
A) Administer live attenuated vaccines during rituximab therapy because B-cell depletion enhances their effect
B) Give needed inactivated vaccines (such as influenza and pneumococcal) before starting rituximab if feasible, because B-cell depletion abolishes vaccine responses for 6 to 9 months; and avoid all live vaccines, which are contraindicated in B-cell-depleted patients because the attenuated strain can cause disseminated infection
C) Defer all vaccines until after rituximab and give live vaccines first once therapy ends, regardless of B-cell recovery
D) Vaccination is unnecessary because rituximab itself provides protection against infection
E) Give live vaccines before therapy and skip inactivated vaccines, since only live vaccines work in immunosuppressed patients
ANSWER: B
Rationale:
Inactivated vaccines such as influenza and pneumococcal should be given before rituximab when feasible, because B-cell depletion blunts vaccine responses for 6 to 9 months. Live vaccines are contraindicated in B-cell-depleted patients because the attenuated strain can cause disseminated infection.
Option A: Option A is incorrect because live vaccines are contraindicated, not enhanced, during B-cell depletion.
Option C: Option C is incorrect because live vaccines remain contraindicated until B-cell recovery, so giving them immediately after therapy is unsafe, and needed inactivated vaccines should be given beforehand.
Option D: Option D is incorrect because rituximab does not confer infection protection; it increases infection risk.
Option E: Option E is incorrect because live vaccines are contraindicated and inactivated vaccines are the appropriate pre-therapy immunizations.
11. [CASE 3 — QUESTION 3]
Continuing with the same patient. After several courses of rituximab over time, he develops subacute progressive neurological deficits including cognitive decline, ataxia, and limb weakness over weeks. Brain magnetic resonance imaging shows white matter lesions without mass effect. What complication should be evaluated, and how is it confirmed?
A) Bacterial meningitis, confirmed by routine cerebrospinal fluid Gram stain and culture
B) Reversible posterior leukoencephalopathy from hypertension, confirmed by lowering blood pressure
C) Hepatitis B reactivation involving the central nervous system, confirmed by serum transaminases
D) Metastatic lymphoma to the brain, confirmed by elevated serum lactate dehydrogenase alone
E) Progressive multifocal leukoencephalopathy from John Cunningham virus reactivation in the central nervous system, confirmed by cerebrospinal fluid John Cunningham virus polymerase chain reaction together with the characteristic magnetic resonance imaging white matter lesions; rituximab should be discontinued, and prognosis is poor with no proven effective treatment
ANSWER: E
Rationale:
Progressive multifocal leukoencephalopathy (PML), caused by John Cunningham virus reactivation in the central nervous system, is a rare but devastating complication of rituximab presenting with subacute progressive neurological deficits and white matter lesions without mass effect on magnetic resonance imaging. Diagnosis is confirmed by cerebrospinal fluid John Cunningham virus polymerase chain reaction alongside the imaging findings; rituximab is discontinued and prognosis is poor with no proven effective treatment.
Option A: Option A is incorrect because bacterial meningitis presents acutely with very different cerebrospinal fluid findings, not subacute white matter lesions without mass effect.
Option B: Option B is incorrect because the progressive multifocal pattern from John Cunningham virus is distinct from hypertension-related posterior leukoencephalopathy and is not confirmed simply by lowering blood pressure.
Option C: Option C is incorrect because hepatitis B reactivation manifests as hepatitis, not progressive white matter brain disease, and transaminases do not confirm a central nervous system process.
Option D: Option D is incorrect because the imaging pattern and clinical course indicate progressive multifocal leukoencephalopathy, and lactate dehydrogenase alone does not confirm brain metastasis.
12. [CASE 3 — QUESTION 4]
Continuing with the same patient. Consider an earlier point in his course: after an initial standard rituximab course, his peripheral B cells are depleted, yet his pre-existing serum immunoglobulin levels remain relatively preserved. Which feature of CD20 (the rituximab target) expression best explains this?
A) CD20 is expressed from the pre-B cell through the mature B cell stage but is absent on terminally differentiated plasma cells; because plasma cells are the principal antibody-secreting population and are not targeted, existing immunoglobulin production is relatively preserved
B) Rituximab selectively spares memory B cells, which maintain immunoglobulin levels
C) Rituximab upregulates immunoglobulin synthesis in the few surviving B cells
D) CD20 is expressed only on T cells, so B-cell antibody production is unaffected
E) Rituximab is cleared too quickly to affect antibody-secreting cells
ANSWER: A
Rationale:
CD20 is present from the pre-B cell stage through the mature B cell stage but is absent on terminally differentiated plasma cells. Because plasma cells are the principal antibody-secreting population and do not express CD20, rituximab depletes B cells while leaving existing immunoglobulin production relatively preserved.
Option B: Option B is incorrect because the explanation is the absence of CD20 on plasma cells, not selective sparing of memory B cells (which express CD20 and are depleted).
Option C: Option C is incorrect because rituximab does not upregulate immunoglobulin synthesis.
Option D: Option D is incorrect because CD20 is a B-cell antigen, not a T-cell antigen.
Option E: Option E is incorrect because rituximab has a long half-life and produces prolonged B-cell depletion, so rapid clearance does not explain preserved immunoglobulin.
13. [CASE 4 — QUESTION 1]
A 64-year-old woman with newly diagnosed multiple myeloma is starting a daratumumab (an anti-CD38 [cyclic ADP-ribose hydrolase] antibody)-based regimen. The care team is reviewing pre-treatment steps specific to this agent. Which step must be completed before the first daratumumab dose to prevent a future transfusion safety problem?
A) Obtain baseline pulmonary function tests because daratumumab causes interstitial lung disease
B) Genotype UGT1A1 (uridine diphosphate-glucuronosyltransferase 1A1) to prevent severe neutropenia
C) Perform baseline ABO/Rh typing and antibody screening and notify the blood bank that the patient will receive daratumumab, because daratumumab binds CD38 on red blood cells and causes pan-reactive false-positive antibody screens that can mask alloantibodies; the blood bank must then use special techniques such as dithiothreitol-treated reagent cells for future compatibility testing
D) Begin hepatitis B antiviral prophylaxis specifically to prevent transfusion reactions
E) Administer prophylactic platelet transfusions before each dose to prevent bleeding
ANSWER: C
Rationale:
Daratumumab binds CD38 on red blood cells and causes pan-reactive false-positive antibody screens that can mask clinically significant alloantibodies. Before the first dose, baseline ABO/Rh typing and antibody screening should be performed and recorded, and the blood bank notified, so that special techniques such as dithiothreitol treatment of reagent cells can be used for all future compatibility testing.
Option A: Option A is incorrect because interstitial lung disease is the signature toxicity of the T-DXd payload, not daratumumab, and pulmonary function testing does not address the transfusion problem.
Option B: Option B is incorrect because UGT1A1 genotyping pertains to sacituzumab govitecan and SN-38 toxicity, not daratumumab transfusion interference.
Option D: Option D is incorrect because hepatitis B prophylaxis addresses reactivation risk, not the blood bank interference.
Option E: Option E is incorrect because prophylactic platelet transfusions do not address the antibody-screen interference and are not indicated.
14. [CASE 4 — QUESTION 2]
Continuing with the same patient. Several weeks into daratumumab she becomes anemic and needs transfusion. The blood bank reports a pan-reactive indirect antiglobulin (indirect Coombs) test. She has no fever, no dark urine, and no laboratory signs of hemolysis. How should this be interpreted and managed?
A) This is an acute hemolytic transfusion reaction; transfusion must be permanently avoided
B) This is daratumumab interference: the antibody binds CD38 on red blood cells, producing a pan-reactive false-positive screen rather than true hemolysis; because it can mask alloantibodies, the blood bank should use special techniques such as dithiothreitol-treated reagent cells (or least-incompatible units in an emergency) to allow safe transfusion
C) The pan-reactive result means her ABO type has changed and no compatible blood exists
D) The result indicates a delayed hemolytic transfusion reaction requiring high-dose corticosteroids before any transfusion
E) The finding is meaningless and the blood bank need not be informed of daratumumab exposure
ANSWER: B
Rationale:
Daratumumab binds CD38 on red blood cells and produces a pan-reactive false-positive indirect antiglobulin test; the absence of hemolysis markers confirms this is laboratory interference, not true hemolysis. Because the interference can mask alloantibodies, the blood bank uses special techniques such as dithiothreitol treatment of reagent cells, or least-incompatible units in an emergency, to enable safe transfusion.
Option A: Option A is incorrect because this is test interference, not an acute hemolytic transfusion reaction, and transfusion is achievable.
Option C: Option C is incorrect because daratumumab does not change the ABO type.
Option D: Option D is incorrect because this is not a delayed hemolytic transfusion reaction and does not call for corticosteroids before transfusion.
Option E: Option E is incorrect because the interference is clinically important and the blood bank must be informed to avoid masking true alloantibodies.
15. [CASE 4 — QUESTION 3]
Continuing with the same patient. The team is finalizing the pre-medication protocol for her initial daratumumab infusions to reduce infusion-related reactions. Which pre-medication regimen is characteristic for daratumumab, distinguishing it from the simpler regimens used for some other antibodies?
A) High-dose diphenhydramine alone, because daratumumab reactions are purely immunoglobulin E-mediated
B) No pre-medication, because daratumumab does not cause infusion reactions
C) Epinephrine prophylaxis before every infusion, since anaphylaxis is expected
D) Dexamethasone (a corticosteroid), an antihistamine, acetaminophen, and a leukotriene modifier (montelukast) for the initial infusions, reflecting that daratumumab infusion reactions are predominantly cytokine-release reactions, especially during the first infusion
E) A topoisomerase inhibitor given prophylactically to blunt the reaction
ANSWER: D
Rationale:
Daratumumab infusion-related reactions are predominantly cytokine-release reactions, most frequent with the first infusion. The characteristic pre-medication regimen combines a corticosteroid (dexamethasone), an antihistamine, acetaminophen, and a leukotriene modifier (montelukast) for the initial infusions, a more intensive regimen than the corticosteroid-antihistamine-acetaminophen combination used for some other antibodies.
Option A: Option A is incorrect because daratumumab reactions are predominantly cytokine-release, not purely immunoglobulin E-mediated, so antihistamine alone is insufficient.
Option B: Option B is incorrect because daratumumab does cause infusion reactions and requires pre-medication.
Option C: Option C is incorrect because routine epinephrine prophylaxis is not standard; anaphylaxis is not the expected reaction type.
Option E: Option E is incorrect because a topoisomerase inhibitor is a cytotoxic payload, not an infusion-reaction pre-medication.
16. [CASE 4 — QUESTION 4]
Continuing with the same patient. She completes daratumumab therapy. Three months after her last dose she requires transfusion at another hospital, and the antibody screen is again pan-reactive. The new facility is unaware of her prior daratumumab. What is the best explanation and action?
A) Daratumumab interference with the antibody screen can persist for up to approximately 6 months after the last dose, so a pan-reactive screen 3 months out is consistent with residual interference; the new facility should be informed of the recent daratumumab exposure and use special techniques such as dithiothreitol-treated reagent cells, and a patient identification card or alert helps communicate this across facilities
B) The interference always resolves within 1 week, so this result must represent a new alloantibody requiring no special technique
C) The patient's blood type has permanently changed, making transfusion impossible
D) The pan-reactive screen 3 months out indicates active hemolysis and contraindicates transfusion
E) Because therapy is finished, no special handling is needed and a routine crossmatch is fully reliable
ANSWER: A
Rationale:
Daratumumab binds CD38 on red blood cells and its interference with the antibody screen can persist for up to roughly 6 months after the last dose. A pan-reactive screen 3 months after completion is therefore consistent with residual interference, not necessarily a new alloantibody. The treating facility should be informed of the recent daratumumab exposure and use special techniques such as dithiothreitol-treated reagent cells; a patient identification card or alert helps carry this information across facilities.
Option B: Option B is incorrect because the interference can last about 6 months, not 1 week.
Option C: Option C is incorrect because daratumumab does not permanently change the blood type.
Option D: Option D is incorrect because the pan-reactivity is interference, not evidence of active hemolysis.
Option E: Option E is incorrect because the interference outlasts dosing, so special handling remains necessary and routine crossmatch may be unreliable.
17. [CASE 5 — QUESTION 1]
A 51-year-old woman has metastatic triple-negative breast cancer (TNBC, lacking estrogen receptor, progesterone receptor, and HER2 [human epidermal growth factor receptor 2] expression) that has progressed after two prior systemic therapies. Her oncologist is considering an antibody-drug conjugate targeting a cell-surface glycoprotein overexpressed in this tumor type. Which agent and target/payload combination fits this clinical scenario?
A) Trastuzumab emtansine, a HER2-targeted conjugate with a maytansinoid payload
B) Brentuximab vedotin, a CD30-targeted conjugate with a monomethyl auristatin E payload
C) Rituximab, an anti-CD20 antibody without a cytotoxic payload
D) Bevacizumab, an anti-VEGF antibody used for angiogenesis inhibition
E) Sacituzumab govitecan, an antibody-drug conjugate targeting TROP-2 (trophoblast cell surface antigen 2), which is overexpressed in triple-negative breast cancer, and delivering the topoisomerase I inhibitor payload SN-38 (the active metabolite of irinotecan); it is indicated for metastatic triple-negative breast cancer after at least two prior therapies
ANSWER: E
Rationale:
Sacituzumab govitecan targets TROP-2, a cell-surface glycoprotein overexpressed in triple-negative breast cancer, and delivers the topoisomerase I inhibitor SN-38 (the active metabolite of irinotecan). It is indicated for metastatic triple-negative breast cancer after at least two prior therapies, matching this scenario.
Option A: Option A is incorrect because trastuzumab emtansine targets HER2, which this triple-negative tumor lacks.
Option B: Option B is incorrect because brentuximab vedotin targets CD30 on lymphomas, not TROP-2 on breast cancer.
Option C: Option C is incorrect because rituximab is an anti-CD20 antibody for B-cell disease and carries no cytotoxic payload.
Option D: Option D is incorrect because bevacizumab is an anti-VEGF antibody, not a TROP-2-targeted conjugate for this indication.
18. [CASE 5 — QUESTION 2]
Continuing with the same patient. Before starting sacituzumab govitecan, pharmacogenomic testing is considered because the SN-38 payload is detoxified by a specific conjugation enzyme. Her genotype returns UGT1A1*28/*28 (homozygous). What is the significance of this result?
A) The genotype increases UGT1A1 (uridine diphosphate-glucuronosyltransferase 1A1) activity, accelerating SN-38 clearance and lowering toxicity risk
B) The genotype affects CYP3A4 (cytochrome P450 3A4) oxidation of SN-38 and predicts reduced efficacy
C) UGT1A1*28/*28 reduces UGT1A1 activity and impairs glucuronidation (the conjugation reaction that detoxifies SN-38), causing SN-38 to accumulate and substantially raising the risk of severe neutropenia and diarrhea
D) The genotype predicts hypersensitivity reactions to the antibody component specifically
E) The genotype has no bearing on SN-38 handling and is irrelevant to this drug
ANSWER: C
Rationale:
SN-38 is detoxified by UGT1A1-mediated glucuronidation. The UGT1A1*28/*28 genotype reduces UGT1A1 expression and activity, impairing glucuronidation so that SN-38 accumulates, substantially raising the risk of severe neutropenia and diarrhea.
Option A: Option A is incorrect because the *28/*28 genotype reduces, not increases, UGT1A1 activity, raising rather than lowering toxicity.
Option B: Option B is incorrect because SN-38 detoxification is by UGT1A1 glucuronidation, not CYP3A4 oxidation, and the genotype predicts toxicity, not reduced efficacy.
Option D: Option D is incorrect because the genotype predicts myelosuppression and diarrhea from payload accumulation, not antibody hypersensitivity.
Option E: Option E is incorrect because the UGT1A1 genotype is directly relevant to SN-38 elimination and toxicity risk.
19. [CASE 5 — QUESTION 3]
Continuing with the same patient. Given her UGT1A1*28/*28 status, the team plans how to administer sacituzumab govitecan as safely as possible. Which management approach is most appropriate?
A) Proceed at full standard dose with no additional monitoring, since the genotype does not change practice
B) Anticipate higher SN-38 toxicity by considering a lower starting dose, providing granulocyte colony-stimulating factor (G-CSF) support for grade 3 or higher neutropenia, managing diarrhea aggressively, and intensifying toxicity monitoring
C) Switch to an anti-EGFR (epidermal growth factor receptor) antibody, since SN-38 conjugates cannot be used in any UGT1A1*28 carrier
D) Increase the dose above standard to overcome the reduced enzyme activity
E) Add prophylactic corticosteroids as the primary strategy to prevent SN-38-related neutropenia
ANSWER: B
Rationale:
Because UGT1A1*28/*28 impairs SN-38 glucuronidation and raises exposure, the appropriate approach anticipates greater toxicity: consider a lower starting dose, provide granulocyte colony-stimulating factor support for grade 3 or higher neutropenia, manage diarrhea aggressively, and intensify monitoring.
Option A: Option A is incorrect because the genotype does change practice toward closer monitoring and dose caution.
Option C: Option C is incorrect because the agent can still be used with dose adjustment and monitoring; switching to an unrelated anti-EGFR antibody is not indicated, and heterozygotes generally tolerate standard dosing.
Option D: Option D is incorrect because increasing the dose would increase, not overcome, SN-38 toxicity in a poor metabolizer.
Option E: Option E is incorrect because corticosteroids are not the primary strategy to prevent SN-38-related neutropenia; dose adjustment and growth factor support are.
20. [CASE 5 — QUESTION 4]
Continuing with the same patient. A colleague who frequently uses monomethyl auristatin E-based conjugates (such as brentuximab vedotin) asks whether this patient should be counseled primarily about peripheral neuropathy. How should the payload class guide the anticipated toxicity counseling?
A) Yes, peripheral neuropathy is the dominant dose-limiting toxicity of SN-38 conjugates and should be the main counseling point
B) Yes, because all antibody-drug conjugates share peripheral neuropathy as their principal toxicity regardless of payload
C) The patient should be counseled primarily about interstitial lung disease, since SN-38 causes pneumonitis
D) Peripheral neuropathy is characteristic of monomethyl auristatin E-containing conjugates (which disrupt axonal microtubules), not of the SN-38 topoisomerase I inhibitor payload; this patient should instead be counseled primarily about neutropenia and diarrhea, the signature toxicities of SN-38
E) Payload class is irrelevant to toxicity, so the counseling is the same for every conjugate
ANSWER: D
Rationale:
Peripheral neuropathy is the signature toxicity of monomethyl auristatin E-containing conjugates (brentuximab vedotin, polatuzumab vedotin) because that microtubule-inhibitor payload disrupts axonal microtubule transport. The SN-38 payload of sacituzumab govitecan is a topoisomerase I inhibitor whose characteristic toxicities are neutropenia and diarrhea, so counseling should focus on those rather than neuropathy.
Option A: Option A is incorrect because peripheral neuropathy is not the dominant toxicity of SN-38 conjugates.
Option B: Option B is incorrect because antibody-drug conjugates do not all share neuropathy; toxicity tracks payload class.
Option C: Option C is incorrect because interstitial lung disease is the signature toxicity of the deruxtecan payload, not SN-38.
Option E: Option E is incorrect because payload class clearly predicts distinct toxicities.
21. [CASE 6 — QUESTION 1]
A 60-year-old woman has hormone receptor-positive metastatic breast cancer that has progressed after endocrine therapy and one line of chemotherapy. Repeat biopsy shows HER2 (human epidermal growth factor receptor 2) immunohistochemistry 1+ (HER2-low), below the historical threshold for HER2-positivity. A pivotal randomized trial defined a new standard of care for this previously HER2-negative, HER2-low population by demonstrating superior progression-free and overall survival versus physician's choice chemotherapy. Which agent does that trial support for her?
A) Trastuzumab emtansine, on the basis of activity in HER2-low disease
B) Pertuzumab plus trastuzumab, as dual blockade for HER2-low disease
C) Cetuximab, an anti-EGFR (epidermal growth factor receptor) antibody, for HER2-low breast cancer
D) Bevacizumab plus chemotherapy as the HER2-low standard
E) Trastuzumab deruxtecan (T-DXd), whose high drug-to-antibody ratio (approximately 8) and membrane-permeable, bystander-capable topoisomerase I inhibitor payload produce activity even at low HER2 expression, establishing it as standard of care in HER2-low breast cancer in the trial of T-DXd versus physician's choice chemotherapy
ANSWER: E
Rationale:
The pivotal HER2-low trial randomized patients to trastuzumab deruxtecan versus physician's choice chemotherapy and showed superior progression-free and overall survival, establishing T-DXd as standard of care for HER2-low breast cancer. Its high drug-to-antibody ratio and membrane-permeable, bystander-capable payload account for activity at low HER2 expression.
Option A: Option A is incorrect because trastuzumab emtansine, with its non-cleavable linker and membrane-impermeant metabolite, is not the agent that defined the HER2-low standard.
Option B: Option B is incorrect because pertuzumab plus trastuzumab is dual blockade for HER2-positive disease, not the HER2-low standard.
Option C: Option C is incorrect because cetuximab targets EGFR in colorectal and head and neck cancers, not HER2-low breast cancer.
Option D: Option D is incorrect because bevacizumab plus chemotherapy is not the HER2-low standard established by this trial.
22. [CASE 6 — QUESTION 2]
Continuing with the same patient. She begins trastuzumab deruxtecan. After several cycles she develops a dry cough and exertional dyspnea; she is symptomatic but able to perform self-care and is afebrile. Computed tomography shows new bilateral ground-glass opacities, and infectious workup is negative. What is the most appropriate management?
A) Hold trastuzumab deruxtecan and initiate systemic corticosteroids for presumed grade 2 interstitial lung disease (drug-induced pneumonitis), counsel her to report respiratory symptoms promptly, and base resumption on recovery; grade 3 or higher disease requires permanent discontinuation
B) Continue trastuzumab deruxtecan at full dose and attribute symptoms to anxiety
C) Continue the drug unchanged and repeat imaging in 3 months, since ground-glass opacities are always benign
D) Switch immediately to trastuzumab emtansine without evaluating or treating the pulmonary findings
E) Start empiric antibiotics and continue trastuzumab deruxtecan, since pneumonitis does not occur with this agent
ANSWER: A
Rationale:
Interstitial lung disease/pneumonitis is the most serious characteristic toxicity of trastuzumab deruxtecan. New dyspnea with bilateral ground-glass opacities and a negative infectious workup should be treated as drug-induced pneumonitis: for symptomatic disease not limiting self-care (grade 2), hold the drug and start systemic corticosteroids, with resumption based on recovery; grade 3 or higher requires permanent discontinuation. Patients should be counseled to report respiratory symptoms promptly.
Option B: Option B is incorrect because continuing full-dose therapy risks progression to severe or fatal lung injury.
Option C: Option C is incorrect because these opacities in this context are not benign and require action.
Option D: Option D is incorrect because switching agents without evaluating and managing the pneumonitis is unsafe and premature.
Option E: Option E is incorrect because pneumonitis does occur with trastuzumab deruxtecan and is not addressed by antibiotics alone.
23. [CASE 6 — QUESTION 3]
Continuing with the same patient. Later in her course, on a bevacizumab (an anti-VEGF [vascular endothelial growth factor])-containing regimen for a different indication, she is found to need an elective abdominal operation. The surgical team asks about timing relative to bevacizumab. What is the correct perioperative recommendation?
A) Proceed with surgery on schedule, since bevacizumab does not affect wound healing
B) Stop bevacizumab only the day before surgery, which is adequate given its pharmacology
C) Hold bevacizumab for at least 28 days before the elective surgery and do not resume until at least 28 days afterward with complete wound healing confirmed, because its anti-VEGF effect impairs wound healing and raises the risk of dehiscence, anastomotic leak, and bowel perforation, and its long half-life means the effect persists for weeks
D) Give an extra dose of bevacizumab just before surgery to support anastomotic angiogenesis
E) Permanently discontinue bevacizumab because any surgery is an absolute contraindication to further therapy
ANSWER: C
Rationale:
Bevacizumab impairs VEGF-dependent wound healing and increases the risk of dehiscence, anastomotic leak, and bowel perforation, and its half-life of roughly 20 days means the effect persists for weeks. Elective surgery requires holding the drug at least 28 days beforehand and not resuming until at least 28 days afterward with healing confirmed.
Option A: Option A is incorrect because bevacizumab clearly impairs wound healing.
Option B: Option B is incorrect because a one-day hold is far too short given the long half-life.
Option D: Option D is incorrect because additional bevacizumab worsens healing.
Option E: Option E is incorrect because surgery is not a permanent contraindication; therapy can resume after adequate healing.
24. [CASE 6 — QUESTION 4]
Continuing with the same patient. During staging she is found to have a synchronous, biopsy-proven squamous cell carcinoma of the lung with a central cavitating mass. A clinician proposes continuing bevacizumab and extending it to cover the lung primary. What is the most appropriate response regarding bevacizumab and squamous lung cancer?
A) Continue and extend bevacizumab, since squamous lung cancer is a preferred indication for anti-VEGF therapy
B) Continue bevacizumab at a reduced dose, which makes it safe in squamous histology
C) Continue bevacizumab and add an anti-EGFR (epidermal growth factor receptor) antibody, since they are interchangeable in squamous lung cancer
D) Bevacizumab is contraindicated in squamous cell non-small cell lung cancer because of the risk of catastrophic pulmonary hemorrhage from tumor cavitation; it should not be used to cover this squamous primary, and the pivotal trial excluded squamous histology for this reason
E) Bevacizumab is unaffected by lung histology, so no change in plan is needed
ANSWER: D
Rationale:
Bevacizumab is contraindicated in squamous cell non-small cell lung cancer because of the risk of catastrophic pulmonary hemorrhage from tumor cavitation; the pivotal trial excluded squamous histology for this reason, and a central cavitating mass heightens the concern. It should not be extended to cover this squamous primary.
Option A: Option A is incorrect because squamous histology is the contraindicated, not preferred, setting.
Option B: Option B is incorrect because dose reduction does not make bevacizumab safe in squamous histology.
Option C: Option C is incorrect because anti-EGFR antibodies and bevacizumab are not interchangeable and anti-EGFR antibodies are not indicated here.
Option E: Option E is incorrect because lung histology is decisive: squamous histology contraindicates bevacizumab.
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