Chapter 33 — Anti-Cancer Drugs Part I: Pharmacology — Module 6 — Miscellaneous Cytotoxics, Drug Interactions, and Supportive Pharmacology
1. [CASE 1 — QUESTION 1]
A 26-year-old woman with sickle cell disease has had recurrent vaso-occlusive crises and one prior episode of acute chest syndrome. She is not pregnant and is started on hydroxyurea as disease-modifying therapy, with a plan for periodic complete blood count monitoring. Her hematologist explains that the same drug is also used to lower elevated cell counts in myeloproliferative disorders. By what mechanism does hydroxyurea act at the level of DNA synthesis?
A) It alkylates DNA, producing interstrand cross-links independent of cell-cycle phase
B) It scavenges the tyrosyl free radical in the R2 subunit of ribonucleotide reductase, halting reduction of ribonucleotides to deoxyribonucleotides and arresting cells in S phase
C) It stabilizes microtubules, arresting cells in mitosis
D) It inhibits topoisomerase II, stabilizing cleavable complexes and causing strand breaks
E) It depletes circulating asparagine, starving cells of an essential amino acid
ANSWER: B
Rationale:
Hydroxyurea inhibits ribonucleotide reductase by scavenging the stable tyrosyl free radical in the enzyme's R2 subunit, which halts the reduction of ribonucleoside diphosphates to deoxyribonucleoside diphosphates and starves DNA synthesis of precursors, arresting cells in S phase.
Option A: Option A is incorrect because alkylation with interstrand cross-links describes alkylating agents, which act independently of cell-cycle phase, not hydroxyurea.
Option C: Option C is incorrect because microtubule stabilization with mitotic arrest is the taxane mechanism.
Option D: Option D is incorrect because topoisomerase II inhibition with cleavable-complex stabilization describes etoposide and anthracyclines.
Option E: Option E is incorrect because asparagine depletion is the asparaginase mechanism and has nothing to do with ribonucleotide reductase.
2. [CASE 1 — QUESTION 2]
Continuing with the same patient. After several months of hydroxyurea, her vaso-occlusive crisis frequency falls substantially. Which mechanism best explains this clinical benefit in sickle cell disease?
A) Hydroxyurea increases fetal hemoglobin production by reactivating gamma-globin expression, and fetal hemoglobin does not polymerize, reducing the fraction of sickle hemoglobin available to sickle
B) Hydroxyurea directly anticoagulates the blood, preventing microvascular occlusion
C) Hydroxyurea corrects the underlying beta-globin gene mutation in erythroid precursors
D) Hydroxyurea blocks splenic sequestration of sickled erythrocytes
E) Hydroxyurea raises the total red cell mass, diluting the abnormal hemoglobin
ANSWER: A
Rationale:
Hydroxyurea increases fetal hemoglobin by reactivating gamma-globin gene expression, and because fetal hemoglobin does not participate in polymerization, a higher fetal hemoglobin fraction reduces the sickle hemoglobin available to polymerize, decreasing vaso-occlusive crises, acute chest syndrome, and transfusion need.
Option B: Option B is incorrect because hydroxyurea is not an anticoagulant and does not act by thinning the blood.
Option C: Option C is incorrect because hydroxyurea does not edit or correct the beta-globin mutation; the mutant gene remains.
Option D: Option D is incorrect because the benefit is not mediated by blocking splenic clearance of sickled cells.
Option E: Option E is incorrect and backward because hydroxyurea is myelosuppressive and tends to lower, not raise, the red cell mass.
3. [CASE 1 — QUESTION 3]
Continuing with the same patient. During dose titration she is monitored for the dose-limiting toxicity of hydroxyurea. Which laboratory finding is the principal dose-limiting toxicity requiring periodic surveillance?
A) Elevated transaminases from hepatocellular injury
B) Rising serum creatinine from tubular toxicity
C) Prolonged QT interval on electrocardiography
D) Myelosuppression with neutropenia and thrombocytopenia detected on the complete blood count
E) Hyperkalemia from tumor lysis
ANSWER: D
Rationale:
The dose-limiting toxicity of hydroxyurea is myelosuppression, manifesting as neutropenia and thrombocytopenia, which is why periodic complete blood count monitoring is required during therapy; macrocytosis is also expected but does not require dose reduction.
Option A: Option A is incorrect because hepatocellular injury with transaminase elevation is not the characteristic dose-limiting toxicity of hydroxyurea.
Option B: Option B is incorrect because, although hydroxyurea is renally cleared and requires dose adjustment in renal impairment, tubular toxicity with rising creatinine is not its dose-limiting effect.
Option C: Option C is incorrect because QT prolongation is not a recognized hydroxyurea toxicity.
Option E: Option E is incorrect because hyperkalemia from tumor lysis relates to rapid cytoreduction of bulky malignancy rather than to chronic hydroxyurea dosing in sickle cell disease.
4. [CASE 1 — QUESTION 4]
Continuing with the same patient. Over the following year she develops chronic kidney disease with a creatinine clearance of 45 mL/min. How should this affect her hydroxyurea management?
A) No adjustment is needed because hydroxyurea is eliminated entirely by hepatic metabolism
B) The dose should be increased because renal impairment accelerates hydroxyurea clearance
C) The dose should be reduced because hydroxyurea undergoes renal excretion and declining clearance raises drug exposure and myelosuppression risk
D) Hydroxyurea should be replaced with an alkylating agent, which is safer in renal impairment
E) Renal function is irrelevant because hydroxyurea is not excreted by the kidney
ANSWER: C
Rationale:
Hydroxyurea undergoes renal excretion, so declining renal function reduces clearance and raises drug exposure, increasing the risk of myelosuppression; dose reduction is required as creatinine clearance falls, generally below about 60 mL/min.
Option A: Option A is incorrect because hydroxyurea is not eliminated entirely hepatically; renal excretion is an important route.
Option B: Option B is incorrect and backward because renal impairment slows rather than accelerates clearance, so the dose should fall, not rise.
Option D: Option D is incorrect because alkylating agents are not a safer substitute in renal impairment and would not address her sickle cell indication.
Option E: Option E is incorrect because the kidney is a relevant elimination route for hydroxyurea, making renal function clinically important.
5. [CASE 2 — QUESTION 1]
A 7-year-old boy with newly diagnosed T-cell acute lymphoblastic leukemia begins an induction regimen that includes pegaspargase. His parents ask how an enzyme can act as chemotherapy. Which mechanism explains the antileukemic effect and its selectivity for the blasts?
A) Asparaginase inhibits ribonucleotide reductase, blocking DNA synthesis selectively in blasts
B) Asparaginase alkylates leukemic DNA, producing cross-links that spare normal cells
C) Asparaginase stabilizes microtubules in dividing blasts, arresting them in mitosis
D) Asparaginase blocks the proteasome in blasts, triggering the unfolded protein response
E) Asparaginase hydrolyzes circulating asparagine, and blasts with low asparagine synthetase cannot synthesize their own, so they are selectively starved of an amino acid required for protein synthesis
ANSWER: E
Rationale:
Asparaginase hydrolyzes circulating L-asparagine, and many acute lymphoblastic leukemia blasts express very low asparagine synthetase, leaving them unable to synthesize asparagine de novo; depletion therefore selectively starves these auxotrophic blasts of an amino acid essential for protein synthesis while sparing normal cells with intact synthetase.
Option A: Option A is incorrect because ribonucleotide reductase inhibition is the hydroxyurea mechanism, not asparaginase.
Option B: Option B is incorrect because asparaginase does not alkylate DNA.
Option C: Option C is incorrect because microtubule stabilization is the taxane mechanism.
Option D: Option D is incorrect because, although asparagine depletion does induce endoplasmic reticulum stress and the unfolded protein response downstream, the primary action is enzymatic depletion of asparagine rather than direct proteasome inhibition.
6. [CASE 2 — QUESTION 2]
Continuing with the same patient. He tolerates pegaspargase without rash, hypotension, or other allergic features, but therapeutic drug monitoring shows trough asparaginase activity below target. Which interpretation and action is correct?
A) This is overt anaphylaxis; discontinue asparaginase permanently
B) This is expected pharmacokinetic variability; no change is needed
C) This is silent inactivation from neutralizing antibodies; switch to a non-cross-reacting preparation such as Erwinia asparaginase and confirm adequate asparagine depletion
D) This is pancreatitis; obtain a lipase and hold therapy
E) This is hyperglycemia; start insulin and continue the same preparation
ANSWER: C
Rationale:
Subtherapeutic asparaginase activity despite full clinical tolerance is the signature of silent inactivation, in which neutralizing antibodies reduce enzyme activity without a hypersensitivity reaction; the appropriate response is to switch to a non-cross-reacting preparation such as Erwinia asparaginase and confirm adequate asparagine depletion thereafter.
Option A: Option A is incorrect because there are no features of anaphylaxis, and the issue is neutralized activity rather than an allergic emergency.
Option B: Option B is incorrect because inadequate depletion is a clinically meaningful loss of efficacy, not benign variability to be ignored.
Option D: Option D is incorrect because the scenario lacks the pain and lipase elevation of pancreatitis.
Option E: Option E is incorrect because there is no hyperglycemia described, and continuing a neutralized preparation would perpetuate under-treatment.
7. [CASE 2 — QUESTION 3]
Continuing with the same patient. Three weeks into therapy he develops headache, lethargy, and a focal seizure, and imaging confirms cerebral venous sinus thrombosis. Which explanation and management approach is correct?
A) Asparaginase activates platelets directly; treat with aspirin alone and continue asparaginase
B) Asparaginase suppresses hepatic synthesis of natural anticoagulants such as antithrombin III and protein C alongside procoagulant factors, tipping some patients toward thrombosis; treat with systemic anticoagulation, monitor coagulation parameters, and replace fibrinogen if critically low
C) The thrombosis reflects hyperviscosity from a high asparagine level; treat with phlebotomy
D) The event is unrelated to asparaginase; no change in therapy is warranted
E) Asparaginase raises antithrombin III, which paradoxically promotes clotting; lower the dose
ANSWER: B
Rationale:
Asparaginase broadly reduces hepatic protein synthesis, lowering both procoagulant factors and the natural anticoagulants antithrombin III and protein C; when the anticoagulant proteins fall disproportionately, the balance can tip toward thrombosis, and cerebral venous sinus thrombosis is a recognized serious complication. Management includes systemic anticoagulation, monitoring of coagulation parameters, and replacement of fibrinogen (for example with cryoprecipitate) when critically low.
Option A: Option A is incorrect because the mechanism is a coagulation-protein imbalance rather than direct platelet activation, and aspirin alone is inadequate for established sinus thrombosis.
Option C: Option C is incorrect because asparaginase depletes rather than raises asparagine, and the event is not a hyperviscosity phenomenon.
Option D: Option D is incorrect because the thrombosis is a known asparaginase complication rather than an unrelated event.
Option E: Option E inverts the pharmacology because asparaginase lowers antithrombin III rather than raising it.
8. [CASE 2 — QUESTION 4]
Continuing with the same patient. After recovery and resumption of therapy, he later develops severe epigastric pain radiating to the back with a serum lipase five times the upper limit of normal. Which is the correct interpretation and next step?
A) This is asparaginase-associated pancreatitis; hold asparaginase, provide supportive care, and avoid rechallenge in clinically significant or severe cases
B) This is recurrent cerebral venous sinus thrombosis; resume anticoagulation
C) This is silent inactivation; switch preparations and continue without interruption
D) This is an expected infusion reaction; premedicate and continue at full dose
E) This is hyperglycemia; the lipase elevation is incidental and requires no action
ANSWER: A
Rationale:
Severe epigastric pain radiating to the back with markedly elevated lipase identifies asparaginase-associated pancreatitis, a recognized and potentially severe toxicity; the correct step is to hold asparaginase and provide supportive care, generally avoiding rechallenge in clinically significant or severe pancreatitis.
Option B: Option B is incorrect because the presentation is pancreatitis rather than recurrent sinus thrombosis, which would present with neurologic features.
Option C: Option C is incorrect because silent inactivation is an asymptomatic loss of enzyme activity, not an acute painful pancreatitis.
Option D: Option D is incorrect because this is pancreatitis rather than an infusion reaction, and continuing at full dose would be unsafe.
Option E: Option E is incorrect because the elevated lipase with characteristic pain is diagnostic of pancreatitis rather than an incidental finding attributable to hyperglycemia.
9. [CASE 3 — QUESTION 1]
A 64-year-old man with newly diagnosed multiple myeloma is started on lenalidomide combined with dexamethasone. The fellow on service asks how lenalidomide kills myeloma cells at the molecular level. Which mechanism is correct?
A) Lenalidomide inhibits the proteasome directly, causing accumulation of misfolded proteins
B) Lenalidomide alkylates myeloma DNA, producing interstrand cross-links
C) Lenalidomide inhibits ribonucleotide reductase, arresting myeloma cells in S phase
D) Lenalidomide binds the E3 ubiquitin ligase adaptor cereblon and redirects it to degrade the transcription factors Ikaros and Aiolos, removing drivers of myeloma survival and lifting suppression of interleukin-2 in T cells
E) Lenalidomide depletes circulating asparagine, starving myeloma cells of an essential amino acid
ANSWER: D
Rationale:
Lenalidomide binds the E3 ubiquitin ligase adaptor cereblon and changes its substrate specificity so that the transcription factors Ikaros and Aiolos are recruited and degraded by the proteasome; their loss removes drivers of myeloma survival such as IRF4 and MYC, and degradation of the same factors in regulatory T cells lifts suppression of interleukin-2 to add an immunostimulatory effect.
Option A: Option A is incorrect because direct proteasome inhibition is the bortezomib mechanism, not lenalidomide, which co-opts the ubiquitin-proteasome system through cereblon.
Option B: Option B is incorrect because lenalidomide does not alkylate DNA.
Option C: Option C is incorrect because ribonucleotide reductase inhibition is the hydroxyurea mechanism.
Option E: Option E is incorrect because asparagine depletion is the asparaginase mechanism and is unrelated to cereblon.
10. [CASE 3 — QUESTION 2]
Continuing with the same patient. Before the first dose, the team addresses a mandatory preventive measure specific to this regimen. He has a prior unprovoked deep vein thrombosis. Which approach is correct?
A) No thromboprophylaxis is required because dexamethasone neutralizes the clotting risk of lenalidomide
B) Thromboprophylaxis is mandatory, and because of his prior thrombosis he warrants low molecular weight heparin or therapeutic-intensity anticoagulation rather than aspirin alone
C) Begin antifungal prophylaxis as the principal preventive measure and omit anticoagulation
D) Begin an anticonvulsant to prevent lenalidomide neurotoxicity instead of anticoagulation
E) Defer lenalidomide indefinitely because prior thrombosis is an absolute contraindication
ANSWER: B
Rationale:
Lenalidomide combined with dexamethasone substantially raises venous thromboembolism risk, so thromboprophylaxis is mandatory; a patient with prior unprovoked thrombosis is higher risk and warrants low molecular weight heparin or therapeutic-intensity anticoagulation rather than aspirin alone, which is reserved for lower-risk patients.
Option A: Option A is incorrect because dexamethasone adds to rather than offsets the thrombotic risk.
Option C: Option C is incorrect because antifungal prophylaxis does not address the defining thrombotic risk.
Option D: Option D is incorrect because lenalidomide is relatively non-neurotoxic and does not require anticonvulsant prophylaxis, which would not address clotting.
Option E: Option E is incorrect because prior thrombosis is not an absolute contraindication; it intensifies the required prophylaxis rather than precluding therapy.
11. [CASE 3 — QUESTION 3]
Continuing with the same patient. His baseline labs reveal a creatinine clearance of 35 mL/min. How does this affect lenalidomide dosing, and why?
A) No adjustment is needed because lenalidomide is metabolized by CYP3A4 independent of renal function
B) The dose should be increased because renal impairment accelerates lenalidomide clearance
C) Lenalidomide should be replaced by thalidomide, which is renally cleared and safer here
D) Renal function is irrelevant because lenalidomide is eliminated by biliary excretion
E) The dose should be reduced according to the degree of renal impairment because lenalidomide is predominantly renally excreted, so reduced clearance raises exposure and toxicity risk
ANSWER: E
Rationale:
Lenalidomide is cleared predominantly by the kidney as largely unchanged drug, so its dose must be reduced according to the degree of renal impairment because reduced clearance raises exposure and the risk of myelosuppression.
Option A: Option A is incorrect because lenalidomide does not depend on CYP3A4 metabolism; it is renally eliminated.
Option B: Option B is incorrect and backward because renal impairment slows clearance, requiring a lower rather than higher dose.
Option C: Option C is incorrect because thalidomide is not renally cleared and is not a safer substitute in renal impairment.
Option D: Option D is incorrect because lenalidomide is renally excreted rather than eliminated by biliary excretion, making renal function highly relevant.
12. [CASE 3 — QUESTION 4]
Continuing with the same patient. He responds well and proceeds to autologous stem cell transplantation followed by lenalidomide maintenance. Which statement about maintenance therapy is correct?
A) Lenalidomide maintenance prolongs progression-free survival but carries a small, statistically significant increase in second primary malignancies, and as an immunomodulatory drug it is distributed under a mandatory REMS program with pregnancy-prevention requirements
B) Lenalidomide maintenance has no effect on progression-free survival and is given only for symptom control
C) Lenalidomide maintenance eliminates any risk of second malignancy because it is immunostimulatory
D) Lenalidomide maintenance requires no REMS oversight once the patient is past reproductive age
E) Lenalidomide maintenance must be combined with an alkylating agent to be effective
ANSWER: A
Rationale:
Lenalidomide maintenance after autologous transplantation prolongs progression-free survival but is associated with a small, statistically significant increase in second primary malignancies, particularly hematologic ones; as an immunomodulatory drug it is distributed only under a mandatory REMS program with pregnancy-prevention requirements.
Option B: Option B is incorrect because maintenance does improve progression-free survival rather than serving only symptom control.
Option C: Option C is incorrect because the immunostimulatory activity does not eliminate the second-malignancy risk; that risk is in fact modestly increased.
Option D: Option D is incorrect because REMS requirements apply to the drug's distribution regardless of an individual patient's reproductive status.
Option E: Option E is incorrect because lenalidomide maintenance is effective as monotherapy and does not require combination with an alkylating agent.
13. [CASE 4 — QUESTION 1]
A 34-year-old woman undergoing chemotherapy for acute lymphoblastic leukemia is receiving vincristine. She develops invasive aspergillosis and is started on voriconazole. Within two weeks she has worsening foot drop, areflexia, and severe constipation. Which mechanism explains this deterioration?
A) Voriconazole induces CYP3A4, lowering vincristine exposure and causing withdrawal-like symptoms
B) Voriconazole displaces vincristine from albumin, transiently lowering free drug
C) Voriconazole inhibits CYP3A4-mediated vincristine metabolism, raising vincristine exposure and producing severe neurotoxicity
D) Voriconazole and vincristine form an inactive complex that deposits in peripheral nerves
E) Voriconazole blocks vincristine renal excretion, raising its plasma level
ANSWER: C
Rationale:
Voriconazole is a potent CYP3A4 inhibitor, and vincristine is cleared by CYP3A4; inhibition slows vincristine metabolism, raises its exposure at standard doses, and can precipitate severe neurotoxicity such as motor weakness, areflexia, and autonomic constipation.
Option A: Option A is incorrect because voriconazole inhibits rather than induces CYP3A4, and the toxicity reflects increased rather than decreased exposure.
Option B: Option B is incorrect because the interaction is metabolic rather than a protein-binding displacement, which would not produce this sustained toxicity.
Option D: Option D is incorrect because no inactive drug complex forms; the mechanism is reduced metabolic clearance.
Option E: Option E is incorrect because vincristine is cleared mainly by hepatic CYP3A4-mediated metabolism rather than by renal excretion.
14. [CASE 4 — QUESTION 2]
Continuing with the same patient. After recovery, she is later transitioned to imatinib for a Philadelphia chromosome-positive disease component, and rifampin is added for latent tuberculosis reactivation. Which consequence and management response is correct?
A) Rifampin induces CYP3A4 and reduces imatinib exposure by roughly 70%, risking treatment failure, so the imatinib dose should be increased or a non-inducing antitubercular substituted
B) Rifampin inhibits CYP3A4 and raises imatinib exposure, requiring a dose reduction
C) Rifampin has no interaction with imatinib because imatinib is renally cleared unchanged
E) Rifampin and imatinib form a chelate that is poorly absorbed, raising rifampin levels
ANSWER: A
Rationale:
Rifampin is a potent CYP3A4 inducer, and imatinib is a CYP3A4 substrate; co-administration reduces imatinib exposure by approximately 70%, threatening loss of disease control, so the imatinib dose should be increased or a non-inducing antitubercular agent substituted.
Option B: Option B inverts the interaction because rifampin induces rather than inhibits CYP3A4, lowering rather than raising imatinib levels.
Option C: Option C is incorrect because imatinib is metabolized by CYP3A4 rather than cleared renally unchanged, so the interaction is significant.
Option D: Option D is incorrect because the clinically important effect is reduced imatinib exposure, not imatinib-induced rifampin toxicity.
Option E: Option E is incorrect because the interaction is enzyme induction rather than a chelation absorption effect.
15. [CASE 4 — QUESTION 3]
Continuing with the same patient. Years later she is in remission and takes adjuvant tamoxifen for a hormone receptor-positive breast cancer. She becomes depressed, and a colleague suggests paroxetine. Why is this a poor choice, and what is preferred?
A) Paroxetine induces CYP2D6 and raises endoxifen to toxic levels; reduce the tamoxifen dose
B) Paroxetine accelerates tamoxifen clearance with no effect on the active metabolite; no change needed
C) Paroxetine prevents tamoxifen from binding its receptor; switch to an aromatase inhibitor
D) Paroxetine and tamoxifen are both renally cleared and compete for excretion; space the doses
E) Paroxetine potently inhibits CYP2D6, reducing conversion of tamoxifen to active endoxifen by roughly 65 to 75% and potentially compromising efficacy; a CYP2D6-sparing antidepressant such as venlafaxine or escitalopram is preferred
ANSWER: E
Rationale:
Tamoxifen is a prodrug activated by CYP2D6 to endoxifen, and paroxetine is among the most potent CYP2D6 inhibitors, reducing endoxifen formation by roughly 65 to 75% and potentially compromising adjuvant efficacy; a CYP2D6-sparing antidepressant such as venlafaxine or escitalopram is preferred.
Option A: Option A is incorrect because paroxetine inhibits rather than induces CYP2D6 and reduces rather than raises endoxifen.
Option B: Option B is incorrect because the interaction reduces formation of the active metabolite rather than being clinically silent.
Option C: Option C is incorrect because paroxetine does not block tamoxifen receptor binding; it impairs metabolic activation.
Option D: Option D is incorrect because the interaction operates through CYP2D6 inhibition rather than competition for renal excretion.
16. [CASE 4 — QUESTION 4]
Continuing with the same patient. She is later treated with a CYP3A4-substrate chemotherapy and, on direct questioning, discloses she takes an over-the-counter herbal supplement for low mood. Which supplement most threatens her chemotherapy exposure, and what is the underlying principle?
A) Echinacea, because it potently inhibits CYP3A4 and raises chemotherapy levels
B) St. John's wort, because it induces CYP3A4 and can reduce plasma concentrations of the chemotherapy, risking treatment failure, which is why direct questioning about herbal and dietary supplements is essential
C) Valerian root, because it chelates the chemotherapy in the gut
D) Melatonin, because it blocks renal excretion of the chemotherapy
E) Ginkgo biloba, because it displaces the chemotherapy from plasma proteins
ANSWER: B
Rationale:
St. John's wort is a potent inducer of CYP3A4 and can lower plasma concentrations of CYP3A4-substrate chemotherapy, risking treatment failure; because patients frequently do not volunteer supplement use, direct questioning about herbal and dietary supplements is essential before starting such therapy.
Option A: Option A is incorrect because echinacea is not a potent CYP3A4 inhibitor and is not the supplement of concern here.
Option C: Option C is incorrect because the St. John's wort interaction is enzyme induction rather than gut chelation by valerian.
Option D: Option D is incorrect because melatonin does not meaningfully block renal excretion of chemotherapy.
Option E: Option E is incorrect because the clinically important mechanism is CYP3A4 induction by St. John's wort rather than protein-binding displacement by ginkgo.
17. [CASE 5 — QUESTION 1]
A 59-year-old man begins oxaliplatin-based therapy for stage III colon cancer. The day after his first infusion he reports tingling in his fingers when handling a cold drink and a brief tight sensation in his throat with cold air, without rash, wheeze, or hypotension. Which is the correct interpretation and counseling?
A) This is the acute cold-triggered sensory syndrome of oxaliplatin, attributed to altered sodium channel kinetics; counsel him to avoid cold food, drink, and air around each infusion
B) This is anaphylaxis; he should self-administer epinephrine and stop oxaliplatin permanently
C) This is the cumulative dorsal root ganglion neuropathy; discontinue oxaliplatin immediately
D) This is a CYP3A4 drug interaction; review his medication list for inhibitors
E) This is laryngeal metastasis; obtain urgent imaging
ANSWER: A
Rationale:
Oxaliplatin characteristically produces an acute, cold-triggered sensory syndrome within hours to days of infusion, including fingertip and pharyngolaryngeal dysesthesias, attributed to cold-induced alteration of sodium channel kinetics; the absence of rash, wheeze, or hypotension distinguishes it from anaphylaxis, and counseling to avoid cold exposure around infusions is the appropriate response.
Option B: Option B is incorrect because the presentation lacks anaphylaxis features and is the recognized cold syndrome rather than an allergic emergency requiring permanent cessation.
Option C: Option C is incorrect because the cumulative dorsal root ganglion neuropathy develops gradually over many cycles rather than acutely after the first infusion.
Option D: Option D is incorrect because this is the intrinsic acute oxaliplatin effect rather than a CYP3A4 interaction.
Option E: Option E is incorrect because the transient cold-triggered pharyngeal sensation is a neurosensory phenomenon rather than a structural metastatic lesion.
18. [CASE 5 — QUESTION 2]
Continuing with the same patient. After several cycles he develops a slowly progressive, persistent numbness in a stocking distribution that no longer depends on cold exposure. How does the mechanism of this cumulative neuropathy differ from taxane-induced neuropathy?
A) Both platinum and taxane neuropathy arise from demyelination of peripheral nerves
B) Platinum neuropathy stabilizes microtubules, while taxane neuropathy forms DNA adducts
C) Platinum and taxane neuropathy share an identical mechanism and differ only in onset
D) Platinum compounds accumulate in dorsal root ganglion neurons and form platinum-DNA adducts that trigger their apoptosis, whereas taxanes disrupt microtubule-based axonal transport, causing distal axonal degeneration
E) Platinum neuropathy is purely motor, while taxane neuropathy is purely autonomic
ANSWER: D
Rationale:
The cumulative platinum neuropathy arises because platinum accumulates in dorsal root ganglion neurons and forms platinum-DNA adducts that trigger apoptosis of these sensory cell bodies, whereas taxane neuropathy results from stabilization of microtubules that disrupts microtubule-based axonal transport and produces distal, length-dependent axonal degeneration.
Option A: Option A is incorrect because neither neuropathy is primarily a demyelinating process.
Option B: Option B reverses the mechanisms, assigning microtubule stabilization to platinum and DNA-adduct formation to taxanes.
Option C: Option C is incorrect because the two mechanisms are distinct rather than identical.
Option E: Option E is incorrect because both neuropathies are predominantly sensory rather than purely motor or purely autonomic.
19. [CASE 5 — QUESTION 3]
Continuing with the same patient. His neuropathy progresses to moderate symptoms that limit instrumental activities of daily living, corresponding to Grade 2 on the standard grading scale, during a curative-intent regimen. What is the most appropriate management principle?
A) Increase the oxaliplatin dose to complete the curative regimen before the neuropathy worsens
B) Ignore the neuropathy grade and base all decisions solely on radiographic tumor response
C) Reduce the dose and reassess, and if neuropathy persists after reduction or worsens to Grade 3, strongly consider discontinuing the offending agent with substitution of a less neurotoxic alternative if the regimen permits
D) Discontinue all chemotherapy immediately at the first sign of any Grade 1 neuropathy
E) Make no change until the neuropathy reaches Grade 4, since lower grades never warrant action
ANSWER: C
Rationale:
Neuropathy grade drives a graded response: Grade 2 neuropathy in a curative regimen warrants a dose reduction and reassessment, and if it persists after reduction or worsens to Grade 3, discontinuation of the offending agent with substitution of a less neurotoxic alternative should be strongly considered when the regimen permits.
Option A: Option A is incorrect and dangerous because worsening neuropathy calls for dose reduction rather than escalation.
Option B: Option B is incorrect because neuropathy grade is a central input to dose decisions rather than something to ignore.
Option D: Option D is incorrect because Grade 1 neuropathy does not by itself require stopping therapy; it warrants documentation and monitoring.
Option E: Option E is incorrect because meaningful action begins at Grade 2 and Grade 3 rather than waiting for Grade 4.
20. [CASE 5 — QUESTION 4]
Continuing with the same patient. After completing treatment, he has persistent painful neuropathy in his feet that interferes with sleep. Which pharmacologic treatment is best supported by evidence as first-line for established painful neuropathy?
A) Calcium and magnesium infusions, which both prevent and treat established neuropathy
B) Duloxetine, the only agent with Level I randomized evidence for established painful chemotherapy-induced peripheral neuropathy, started at 30 mg daily and titrated to 60 mg daily
C) Vitamin E, which has high-quality evidence for treating established neuropathic pain
D) Acetyl-L-carnitine, which reliably reverses established neuropathy
E) Gabapentin, which has Level I evidence specifically in chemotherapy-induced neuropathy
ANSWER: B
Rationale:
Duloxetine is the only agent with Level I randomized evidence for treating established painful chemotherapy-induced peripheral neuropathy and is recommended first-line, typically started at 30 mg daily and titrated to 60 mg daily.
Option A: Option A is incorrect because calcium and magnesium infusions were studied for prevention of oxaliplatin neuropathy and failed, and they do not treat established pain.
Option C: Option C is incorrect because vitamin E lacks high-quality evidence for treating established neuropathic pain.
Option D: Option D is incorrect because acetyl-L-carnitine does not reliably reverse neuropathy and may worsen it in some data.
Option E: Option E is incorrect because gabapentin has shown only equivocal results in chemotherapy-induced neuropathy and lacks the Level I support that duloxetine has.
21. [CASE 6 — QUESTION 1]
A 57-year-old woman treated 7 years ago with high-dose cyclophosphamide-based therapy now presents with pancytopenia, a hypocellular dysplastic marrow, and cytogenetics showing monosomy 7. Which diagnosis and pattern does this represent?
A) Topoisomerase II inhibitor-related leukemia with a balanced KMT2A rearrangement and short latency
B) An unrelated de novo acute leukemia with favorable-risk cytogenetics
C) A reactive cytopenia from recent infection requiring only observation
D) A myeloproliferative neoplasm driven by JAK2 mutation
E) Alkylating agent-related treatment-related myeloid neoplasm, characterized by long latency of roughly 5 to 10 years, an antecedent myelodysplastic phase, and unbalanced loss of chromosome 5 or 7 material
ANSWER: E
Rationale:
The long latency of about 7 years, antecedent dysplastic and hypocellular marrow, and monosomy 7 are characteristic of alkylating agent-related treatment-related myeloid neoplasm following cyclophosphamide, which typically shows unbalanced losses of chromosome 5 or 7 material.
Option A: Option A is incorrect because the balanced KMT2A rearrangement and short latency characterize the topoisomerase II inhibitor pattern rather than the alkylating agent pattern.
Option B: Option B is incorrect because the prior alkylating exposure, long latency, and monosomy 7 mark this as treatment-related rather than an unrelated favorable-risk de novo leukemia.
Option C: Option C is incorrect because treatment-related myeloid neoplasms do not resolve with observation.
Option D: Option D is incorrect because the picture is a dysplastic, hypocellular marrow with monosomy 7 rather than a JAK2-driven myeloproliferative neoplasm.
22. [CASE 6 — QUESTION 2]
Continuing with the same patient. Her oncologist contrasts her disease with that of another survivor who developed acute myeloid leukemia only about two years after an etoposide-containing regimen, without a preceding myelodysplastic phase. Which profile characterizes that second patient's topoisomerase II inhibitor-related disease?
A) Long latency with a preceding myelodysplastic phase and monosomy 7
B) Short latency of about 1 to 3 years, de novo acute myeloid leukemia, and a balanced KMT2A rearrangement at chromosome 11q23
C) Complex karyotype with del(5q) after a decade of latency
D) Normal cytogenetics with no identifiable mechanism
E) Trisomy 8 caused by ribonucleotide reductase inhibition
ANSWER: B
Rationale:
Topoisomerase II inhibitor-related leukemia, as from etoposide, characteristically has a short latency of about 1 to 3 years, presents as de novo acute myeloid leukemia without a preceding myelodysplastic phase, and carries a balanced KMT2A rearrangement at chromosome 11q23.
Option A: Option A describes the alkylating agent pattern with long latency, antecedent myelodysplasia, and monosomy 7.
Option C: Option C is incorrect because it describes the alkylating agent phenotype, with complex karyotype, del(5q), and prolonged latency.
Option D: Option D is incorrect because a defined mechanism and characteristic cytogenetics exist rather than normal cytogenetics with no mechanism.
Option E: Option E is incorrect because ribonucleotide reductase inhibition is the hydroxyurea mechanism and is not the basis of this entity.
23. [CASE 6 — QUESTION 3]
Continuing with the first patient (the alkylating agent-related case with monosomy 7). What is the most accurate statement about her prognosis and the main potentially curative approach?
A) The prognosis is excellent, with cure expected from standard induction chemotherapy alone
B) The disease reliably resolves with growth factor support and requires no definitive therapy
C) The prognosis is favorable because monosomy 7 predicts high sensitivity to induction
D) The prognosis is poor, with low complete remission rates to standard induction, and allogeneic hematopoietic stem cell transplantation is the main potentially curative option in eligible patients
E) The prognosis is determined solely by age and is unaffected by the treatment-related cytogenetics
ANSWER: D
Rationale:
Alkylating agent-related treatment-related myeloid neoplasm with adverse cytogenetics such as monosomy 7 carries a poor prognosis, with low complete remission rates to standard induction chemotherapy; allogeneic hematopoietic stem cell transplantation is the main potentially curative option in eligible patients.
Option A: Option A is incorrect because the prognosis is poor rather than excellent, and standard induction alone is not reliably curative.
Option B: Option B is incorrect because the disease does not resolve with growth factor support and does require definitive therapy.
Option C: Option C is incorrect because monosomy 7 is an adverse rather than favorable cytogenetic feature.
Option E: Option E is incorrect because the adverse treatment-related cytogenetics strongly influence prognosis rather than being irrelevant.
24. [CASE 6 — QUESTION 4]
Continuing with the comparison. Why do topoisomerase II inhibitors such as etoposide generate the balanced KMT2A rearrangement that defines their treatment-related leukemia?
A) They induce point mutations in KMT2A through oxidative base damage
B) They demethylate the KMT2A promoter, silencing the gene
C) They stabilize topoisomerase II cleavable complexes at specific genomic loci including the KMT2A breakpoint region, directly generating the translocation that fuses KMT2A to partner genes
D) They deplete the deoxyribonucleotide pool, causing replication errors at KMT2A
E) They alkylate KMT2A, producing interstrand cross-links that rearrange the gene
ANSWER: C
Rationale:
Topoisomerase II inhibitors stabilize the enzyme's cleavable complexes on DNA at specific genomic loci, including the breakpoint cluster region of KMT2A, and this trapping directly generates the balanced translocation that fuses KMT2A to partner genes, producing the characteristic rearrangement of this treatment-related leukemia.
Option A: Option A is incorrect because the lesion is a balanced translocation from cleavable-complex stabilization rather than point mutation from oxidative base damage.
Option B: Option B is incorrect because the mechanism is not promoter demethylation and gene silencing.
Option D: Option D is incorrect because deoxyribonucleotide depletion describes the hydroxyurea mechanism and does not generate the KMT2A translocation.
Option E: Option E is incorrect because alkylation with interstrand cross-links is the alkylating agent mechanism, not the basis of the topoisomerase II inhibitor-associated rearrangement.
25. [CASE 7 — QUESTION 1]
A 31-year-old woman who is 7 weeks pregnant is newly diagnosed with an aggressive lymphoma. The team weighs the timing of chemotherapy against fetal risk. Which principle governs treatment during this first-trimester window?
A) Chemotherapy is safest now because the small first-trimester fetus is well shielded
B) Only intravenous agents are contraindicated in the first trimester; oral agents are safe
C) Antimetabolites are preferred in the first trimester because their anti-folate action protects the fetus
D) Essentially all cytotoxic chemotherapy is contraindicated in the first trimester because this is the critical window of organogenesis, with high risk of major structural malformations and miscarriage
E) Chemotherapy timing is irrelevant to fetal outcome at any gestational age
ANSWER: D
Rationale:
The first trimester is the period of organogenesis, when major organs and structures are forming, making it the window of greatest vulnerability to structural teratogenicity; essentially all cytotoxic chemotherapy is contraindicated during this period, and miscarriage rates are also elevated.
Option A: Option A is incorrect and dangerously backward because the first trimester is the most hazardous time rather than the safest.
Option B: Option B is incorrect because the route of administration does not determine placental transfer or teratogenic risk.
Option C: Option C inverts the safety profile because antimetabolites such as methotrexate are particularly hazardous in pregnancy rather than fetus-protective.
Option E: Option E is incorrect because gestational timing critically determines fetal risk.
26. [CASE 7 — QUESTION 2]
Continuing with the same patient. Her care is coordinated so that, after the first trimester, treatment can proceed. Which statement about chemotherapy in the second and third trimesters is correct?
A) After the first trimester many regimens, including R-CHOP for aggressive B-cell lymphoma, have been administered in the second and third trimesters with acceptable maternal and neonatal outcomes, and chemotherapy should be stopped several weeks before anticipated delivery
B) Chemotherapy remains absolutely contraindicated through all three trimesters, so treatment must be deferred until after delivery
C) Any agent including methotrexate may be used freely once the first trimester ends
D) Chemotherapy may continue up to the day of delivery without affecting the neonate
E) Only single-agent oral therapy is acceptable after the first trimester
ANSWER: A
Rationale:
After the first trimester, organogenesis is complete and the risk of structural teratogenicity falls, so many regimens including R-CHOP have been given in the second and third trimesters with acceptable maternal and neonatal outcomes; chemotherapy should be stopped several weeks before anticipated delivery to allow drug clearance and reduce neonatal marrow suppression.
Option B: Option B is incorrect because chemotherapy is not absolutely contraindicated throughout pregnancy and need not be deferred entirely past the first trimester.
Option C: Option C is incorrect because antimetabolites such as methotrexate remain relatively contraindicated even after the first trimester.
Option D: Option D is incorrect because chemotherapy should be stopped before delivery rather than continued up to the day of birth, to avoid neonatal myelosuppression.
Option E: Option E is incorrect because acceptable second- and third-trimester options are not limited to single-agent oral therapy.
27. [CASE 7 — QUESTION 3]
Continuing with the same patient. A consultant proposes adding methotrexate to her regimen during the second trimester. Why is this specific agent problematic even after the first trimester?
A) Methotrexate is safe in all trimesters and there is no specific concern
B) Methotrexate is contraindicated only in the third trimester because of bleeding risk
C) Methotrexate is preferred in pregnancy because folate antagonism is selectively fetal-sparing
D) Methotrexate is acceptable provided folic acid is co-administered to the mother
E) Antimetabolites such as methotrexate remain relatively contraindicated throughout pregnancy because their anti-folate mechanism interferes with ongoing fetal development that depends on folate-requiring processes
ANSWER: E
Rationale:
Antimetabolites such as methotrexate remain relatively contraindicated throughout pregnancy because their anti-folate mechanism interferes with folate-dependent processes required for ongoing fetal development, a concern that persists beyond the first trimester.
Option A: Option A is incorrect because methotrexate carries a specific, persistent concern in pregnancy rather than being uniformly safe.
Option B: Option B is incorrect because the concern is not limited to the third trimester or to bleeding risk.
Option C: Option C inverts the pharmacology because folate antagonism is harmful to the developing fetus rather than selectively fetal-sparing.
Option D: Option D is incorrect because co-administered folic acid does not render methotrexate acceptable in pregnancy; the relative contraindication persists.
28. [CASE 7 — QUESTION 4]
Continuing with the same patient. After delivery she requires a regimen containing both carboplatin and doxorubicin, and she has mild renal impairment and a mildly elevated bilirubin. How should each drug be dose-adjusted according to its elimination pathway?
A) Both carboplatin and doxorubicin are renally cleared and dosed by creatinine clearance alone
B) Carboplatin is renally cleared and dosed to a target exposure based on renal function, whereas doxorubicin is hepatically eliminated and reduced according to bilirubin in hepatic impairment
C) Carboplatin is hepatically eliminated and reduced by bilirubin, while doxorubicin is renally cleared and dosed by creatinine clearance
D) Both drugs are hepatically eliminated and require bilirubin-based reduction
E) Neither drug requires adjustment because both are inactivated independent of organ function
ANSWER: B
Rationale:
Dosing follows each drug's elimination route: carboplatin is renally cleared and is dosed to a target exposure based on renal function, whereas doxorubicin is eliminated hepatically and is dose-reduced according to bilirubin in hepatic impairment.
Option A: Option A is incorrect because doxorubicin is hepatically rather than renally eliminated, so creatinine-based dosing does not apply to it.
Option C: Option C reverses the two assignments, incorrectly making carboplatin hepatically eliminated and doxorubicin renally cleared.
Option D: Option D is incorrect because carboplatin is renally cleared rather than hepatically eliminated, so bilirubin-based reduction does not apply to it.
Option E: Option E is incorrect because both drugs require organ-function-based dose adjustment rather than being independent of organ function.
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