Medical Pharmacology: Chapter 34 — Anti-Cancer Drugs Part II -- Module 2 — Targeted Small Molecule Inhibitors: Extended Clinical Cases

Chapter 34 — Anti-Cancer Drugs Part II — Module 2 — Targeted Small Molecule Inhibitors: Extended Clinical Cases

1. [CASE 1 — QUESTION 1] A 57-year-old man presents with widely metastatic melanoma. Molecular testing is pending, and the oncology team is considering a BRAF inhibitor (a drug targeting the BRAF kinase in the MAPK growth pathway). Before any BRAF inhibitor is prescribed, which step is essential, and why?

A) Confirm the patient has normal liver function, because BRAF inhibitors cannot be given to anyone with any hepatic abnormality
B) Confirm a baseline echocardiogram only, because cardiac function is the sole prerequisite for BRAF inhibitor therapy
C) Confirm the tumor carries a BRAF V600E mutation, because BRAF inhibitors benefit V600E-mutant tumors but can paradoxically activate the MAPK pathway and accelerate growth in tumors lacking that mutation, particularly RAS-mutant tumors
D) Confirm the patient is HER2-positive, because BRAF inhibitors require HER2 amplification to work
E) Confirm a negative pregnancy test only, because teratogenicity is the single governing concern for BRAF inhibitors

ANSWER: C

Rationale:

BRAF inhibitor benefit depends on the presence of a BRAF V600E mutation; in a tumor that lacks V600E — especially one carrying a RAS mutation — the same drug paradoxically activates the MAPK pathway and can accelerate tumor growth. Confirming V600E status before prescribing ensures the drug is used only where it helps and not where it harms. The correct choice states this prerequisite and its mechanistic basis.

Option A: Option A is incorrect because, while liver function is monitored, a normal result is not the essential molecular prerequisite, and hepatic abnormality is not an absolute bar.
Option B: Option B is incorrect because, although a MEK inhibitor partner requires cardiac monitoring, an echocardiogram is not the governing prerequisite for selecting a BRAF inhibitor.
Option D: Option D is incorrect because BRAF inhibitor activity depends on BRAF V600E, not HER2 status.
Option E: Option E is incorrect because, although pregnancy must be excluded as for any antineoplastic, the defining prerequisite here is confirming the V600E target.

2. [CASE 1 — QUESTION 2] Continuing with the same patient. Testing confirms BRAF V600E, and he is started on single-agent vemurafenib (a BRAF inhibitor). Two months later he develops a new, firm, rapidly enlarging keratotic skin nodule. What is the most appropriate management?

A) Biopsy the lesion to evaluate for cutaneous squamous-cell carcinoma or keratoacanthoma, and add a MEK inhibitor, which suppresses the paradoxical MAPK pathway activation that drives these lesions
B) Reassure the patient that the nodule is benign and requires no evaluation
C) Stop all BRAF-directed therapy permanently and treat the nodule as metastatic melanoma
D) Start systemic antibiotics for a presumed skin infection and continue vemurafenib unchanged
E) Begin high-dose corticosteroids for a presumed drug hypersensitivity reaction

ANSWER: A

Rationale:

BRAF inhibitor monotherapy paradoxically activates the MAPK pathway in cells with normal BRAF, driving cutaneous squamous-cell carcinoma and keratoacanthoma. A new rapidly growing keratotic nodule should be biopsied, and adding a MEK inhibitor suppresses the paradoxical activation, reducing these lesions while improving tumor control. The correct choice combines biopsy with the mechanism-based addition of a MEK inhibitor.

Option B: Option B is incorrect because a new rapidly enlarging nodule warrants biopsy rather than reassurance.
Option C: Option C is incorrect because the lesion reflects paradoxical activation in normal skin, not melanoma metastasis, and therapy is intensified rather than abandoned.
Option D: Option D is incorrect because the lesion is neoplastic, not infectious, so antibiotics are not the treatment.
Option E: Option E is incorrect because the nodule is not a hypersensitivity reaction and corticosteroids are not the appropriate response.

3. [CASE 1 — QUESTION 3] Continuing with the same patient. A MEK inhibitor (trametinib) is added to his BRAF inhibitor. Which baseline and ongoing monitoring is specifically required because of the MEK inhibitor component of the combination?

A) Audiometry at baseline and before each cycle, because MEK inhibitors characteristically cause hearing loss
B) Serial blood glucose only, because hyperglycemia is the sole MEK inhibitor toxicity
C) Thyroid function only, because MEK inhibitors act primarily on the thyroid gland
D) Baseline and periodic ophthalmologic evaluation for serous retinal detachment, plus baseline and periodic echocardiography for left ventricular ejection fraction reduction (cardiomyopathy)
E) No additional monitoring, because adding a MEK inhibitor introduces no new toxicities

ANSWER: D

Rationale:

MEK inhibitors carry two class toxicities that drive monitoring: serous retinal detachment (chorioretinopathy), requiring baseline and periodic ophthalmologic evaluation, and a reduction in left ventricular ejection fraction (cardiomyopathy), requiring baseline and periodic echocardiography. The correct choice names both monitoring requirements.

Option A: Option A is incorrect because hearing loss is not a MEK inhibitor class effect.
Option B: Option B is incorrect because hyperglycemia is not the MEK inhibitor signature; the relevant toxicities are ocular and cardiac.
Option C: Option C is incorrect because MEK inhibitors do not act primarily on the thyroid, and thyroid testing is not the required monitoring.
Option E: Option E is incorrect because adding a MEK inhibitor does introduce new ocular and cardiac toxicities that mandate specific monitoring.

4. [CASE 1 — QUESTION 4] Continuing with the same patient. He reports a painful sunburn-like reaction after brief outdoor exposure while on vemurafenib. Regarding the dermatologic and febrile toxicities of BRAF/MEK therapy, which counseling-and-management statement is correct?

A) Vemurafenib reduces photosensitivity, so no sun protection is needed during therapy
B) Vemurafenib causes photosensitivity, so strict sun protection is required; and dabrafenib characteristically causes pyrexia, which is managed with dose interruption and brief corticosteroid courses
C) Photosensitivity from vemurafenib is treated by increasing the dose to build tolerance
D) Dabrafenib-associated pyrexia should be ignored, since fever on BRAF therapy is never drug-related
E) Sun exposure should be encouraged because ultraviolet light enhances BRAF inhibitor efficacy

ANSWER: B

Rationale:

Photosensitivity is a class effect of vemurafenib requiring strict sun protection, and pyrexia is prominent with dabrafenib, managed by dose interruption and brief corticosteroid courses. The correct choice pairs the vemurafenib photosensitivity counseling with the dabrafenib pyrexia management.

Option A: Option A is incorrect because vemurafenib increases photosensitivity rather than reducing it, so sun protection is needed.
Option C: Option C is incorrect because photosensitivity is managed by sun protection, not by dose escalation.
Option D: Option D is incorrect because dabrafenib pyrexia is a recognized drug effect that requires active management, not dismissal.
Option E: Option E is incorrect because ultraviolet exposure worsens photosensitivity and does not enhance efficacy.

5. [CASE 2 — QUESTION 1] A 62-year-old postmenopausal woman with estrogen-receptor-positive, HER2-negative metastatic breast cancer begins ribociclib (a CDK4/6 inhibitor) plus letrozole. A scheduled electrocardiogram at the start of cycle two shows a QTc of 495 ms (the heart-rate-corrected electrical recovery interval); she is asymptomatic. What is the most appropriate next step?

A) Continue ribociclib at full dose and recheck the ECG in three months
B) Permanently discontinue CDK4/6 inhibitor therapy and switch immediately to cytotoxic chemotherapy
C) Continue ribociclib and add a fluoroquinolone antibiotic empirically
D) Increase the ribociclib dose to control disease before the QTc worsens
E) Hold ribociclib because the QTc exceeds the interruption threshold, remove concurrent QTc-prolonging drugs, correct electrolytes, and resume at a reduced dose after recovery, not restarting if the QTc recurrently exceeds 500 ms

ANSWER: E

Rationale:

Ribociclib carries the most stringent QTc monitoring protocol among CDK4/6 inhibitors; a QTc above roughly 480 ms mandates interruption, removal of concurrent QTc-prolonging drugs, electrolyte correction, and resumption at a reduced dose after recovery, with permanent discontinuation if the QTc recurrently exceeds 500 ms. The correct choice captures this stepwise management.

Option A: Option A is incorrect because an asymptomatic QTc of 495 ms still exceeds the interruption threshold and cannot be deferred for three months.
Option B: Option B is incorrect because the protocol calls for interruption and dose modification, not immediate permanent discontinuation and a switch to chemotherapy.
Option C: Option C is incorrect because a fluoroquinolone adds further QTc prolongation.
Option D: Option D is incorrect because increasing the dose worsens QTc prolongation.

6. [CASE 2 — QUESTION 2] Continuing with the same patient. Because of recurrent QTc concerns, her team switches her CDK4/6 inhibitor to abemaciclib. Compared with ribociclib, what should she be counseled to expect regarding abemaciclib's dosing schedule and characteristic toxicity?

A) Abemaciclib is dosed three weeks on and one week off and rarely causes diarrhea
B) Abemaciclib is given as a once-monthly injection and characteristically causes hearing loss
C) Abemaciclib is dosed continuously twice daily and characteristically causes substantially more diarrhea than the other CDK4/6 inhibitors, managed with early loperamide and dose reduction
D) Abemaciclib eliminates the neutropenia seen with other CDK4/6 inhibitors and causes no gastrointestinal effects
E) Abemaciclib must be combined with ribociclib to be effective

ANSWER: C

Rationale:

Abemaciclib differs from palbociclib and ribociclib by continuous twice-daily dosing rather than an intermittent schedule, and by a markedly higher rate of diarrhea driven by CDK4/6 inhibition in intestinal crypt cells, managed with early loperamide and dose reduction. The correct choice states both features.

Option A: Option A is incorrect because abemaciclib is dosed continuously, not intermittently, and diarrhea is common rather than rare.
Option B: Option B is incorrect because abemaciclib is an oral twice-daily drug, not a monthly injection, and hearing loss is not its characteristic toxicity.
Option D: Option D is incorrect because abemaciclib still causes neutropenia and prominently causes diarrhea.
Option E: Option E is incorrect because abemaciclib does not require combination with ribociclib and is active as monotherapy.

7. [CASE 2 — QUESTION 3] Continuing with the same patient. Her disease progresses on endocrine-based therapy, and alpelisib (a PI3K-alpha inhibitor) plus fulvestrant is being considered. What molecular step is required before alpelisib can be prescribed?

A) Confirm a PIK3CA mutation by a validated companion diagnostic (tissue or plasma assay), because alpelisib is indicated only for PIK3CA-mutant disease
B) Confirm BRAF V600E status, because alpelisib requires a BRAF mutation to act
C) Confirm FLT3-ITD status, because alpelisib targets FLT3
D) No molecular testing is needed, because alpelisib works regardless of tumor genotype
E) Confirm a germline BRCA mutation, because alpelisib is a PARP inhibitor

ANSWER: A

Rationale:

Alpelisib is approved for PIK3CA-mutant, hormone-receptor-positive, HER2-negative breast cancer, so a PIK3CA mutation must be confirmed by a validated companion diagnostic (tissue or plasma assay) before prescribing. The correct choice states this requirement.

Option B: Option B is incorrect because alpelisib targets PI3K-alpha, not BRAF, and does not require a BRAF mutation.
Option C: Option C is incorrect because alpelisib does not target FLT3.
Option D: Option D is incorrect because alpelisib's indication is genotype-defined and requires confirmed PIK3CA mutation.
Option E: Option E is incorrect because alpelisib is a PI3K-alpha inhibitor, not a PARP inhibitor, and BRCA status does not govern its use.

8. [CASE 2 — QUESTION 4] Continuing with the same patient. A PIK3CA mutation is confirmed and alpelisib is started. At the next cycle her fasting glucose is 305 mg/dL with mild hyperglycemic symptoms and no ketoacidosis. What is the most appropriate management?

A) Stop alpelisib permanently, since hyperglycemia is an absolute contraindication to continued therapy
B) Attribute the glucose to laboratory error and take no action
C) Begin high-dose corticosteroids to counteract the metabolic effect
D) Recognize alpelisib-induced hyperglycemia from PI3K-alpha-mediated insulin resistance; manage with dietary modification and pharmacologic therapy (metformin, with insulin added as needed), monitor fasting glucose, and continue alpelisib with interruption reserved for very severe or refractory hyperglycemia
E) Switch to an mTOR inhibitor, which does not affect glucose

ANSWER: D

Rationale:

Alpelisib blocks PI3K-alpha, the isoform insulin uses for glucose uptake, so hyperglycemia from insulin resistance is its defining toxicity. Management is dietary modification plus pharmacologic therapy — metformin first, with insulin added as needed — alongside fasting glucose monitoring, continuing alpelisib and interrupting only for very severe or refractory hyperglycemia. The correct choice captures the mechanism and stepwise management.

Option A: Option A is incorrect because hyperglycemia at this level is managed rather than being an absolute contraindication.
Option B: Option B is incorrect because a glucose of 305 mg/dL with symptoms is a real, expected drug effect requiring treatment.
Option C: Option C is incorrect because corticosteroids would worsen hyperglycemia.
Option E: Option E is incorrect because mTOR inhibitors also cause hyperglycemia, so the switch would not avoid the problem.

9. [CASE 3 — QUESTION 1] A 73-year-old woman with chronic lymphocytic leukemia and a history of paroxysmal atrial fibrillation needs a BTK inhibitor (a drug blocking Bruton's tyrosine kinase, a survival signal in B-cell cancers). Considering her cardiac history, which initial choice is most appropriate and why?

A) Ibrutinib, because its off-target kinase effects protect against atrial fibrillation
B) A more selective second-generation BTK inhibitor such as acalabrutinib or zanubrutinib, because greater BTK selectivity is associated with a lower rate of atrial fibrillation than ibrutinib
C) Ibrutinib at a higher dose, to overwhelm the arrhythmia
D) No BTK inhibitor can be used once atrial fibrillation has ever occurred
E) Any BTK inhibitor, because they are identical in cardiac risk

ANSWER: B

Rationale:

Ibrutinib's atrial fibrillation is attributed to its off-target kinase inhibition, so the more selective second-generation agents acalabrutinib and zanubrutinib carry a lower rate of atrial fibrillation and are preferred when arrhythmia is a concern. The correct choice states both the agent and the selectivity-based reasoning.

Option A: Option A is incorrect because ibrutinib's off-target effects cause, rather than protect against, the arrhythmia.
Option C: Option C is incorrect because raising the ibrutinib dose increases arrhythmia risk.
Option D: Option D is incorrect because BTK inhibitors can still be used; the strategy is to select a more selective agent and manage the rhythm.
Option E: Option E is incorrect because the agents differ meaningfully in cardiac risk, which is the basis for the choice.

10. [CASE 3 — QUESTION 2] Continuing with the same patient. She was nonetheless started on ibrutinib for access reasons and now has persistent atrial fibrillation with a stroke risk high enough to warrant anticoagulation. How should anticoagulation be managed in the context of ibrutinib?

A) Start warfarin at a standard dose, since ibrutinib does not affect its metabolism
B) Add aspirin to ibrutinib as the anticoagulation strategy
C) Withhold anticoagulation entirely, since atrial fibrillation on ibrutinib does not warrant it
D) Start full-dose warfarin and continue ibrutinib without monitoring the INR
E) Avoid warfarin because ibrutinib's CYP3A4 inhibition elevates the INR; prefer a direct oral anticoagulant with awareness that ibrutinib's P-glycoprotein inhibition raises its levels; and consider switching to acalabrutinib or zanubrutinib to reduce arrhythmia and bleeding risk

ANSWER: E

Rationale:

Anticoagulating a patient on ibrutinib requires applying its interaction and bleeding profile. Ibrutinib inhibits CYP3A4, elevating warfarin levels and the INR, so warfarin is avoided; a direct oral anticoagulant is generally preferred, but ibrutinib's P-glycoprotein inhibition raises direct oral anticoagulant exposure, requiring dose awareness; and switching to a more selective second-generation BTK inhibitor reduces arrhythmia incidence and platelet dysfunction. The correct choice integrates all of these.

Option A: Option A is incorrect because ibrutinib's CYP3A4 inhibition does elevate the INR on warfarin.
Option B: Option B is incorrect because adding aspirin compounds bleeding risk through additive platelet impairment.
Option C: Option C is incorrect because atrial fibrillation with an elevated stroke risk does warrant anticoagulation.
Option D: Option D is incorrect because warfarin is the agent to avoid, and proceeding without INR monitoring would be dangerous.

11. [CASE 3 — QUESTION 3] Continuing with the same patient. Her disease progresses and she is transitioned to venetoclax (a BCL-2 inhibitor). She has bulky lymphadenopathy and a high circulating lymphocyte count. Which initiation plan most appropriately addresses the principal early risk?

A) Start at the full target dose immediately to clear disease quickly, with weekly laboratory checks
B) Begin venetoclax with a strong CYP3A4 inhibitor for antifungal coverage and restrict fluids
C) Use the mandatory stepwise dose ramp-up, provide allopurinol prophylaxis and aggressive hydration, and monitor laboratory values 6 to 8 hours after each dose increase to manage tumor lysis syndrome risk
D) Give a single high loading dose, then observe without laboratory monitoring
E) Premedicate with an agent that prevents tumor cell death to avoid the metabolic effect

ANSWER: C

Rationale:

Venetoclax triggers rapid, synchronous death of BCL-2-dependent tumor cells, and a high tumor burden creates substantial early tumor lysis syndrome risk. The standard mitigation is a mandatory stepwise dose ramp-up with allopurinol prophylaxis, aggressive hydration, and laboratory monitoring 6 to 8 hours after each dose increase. The correct choice captures this.

Option A: Option A is incorrect and dangerous because the full starting dose maximizes simultaneous cell death and tumor lysis.
Option B: Option B is incorrect because a strong CYP3A4 inhibitor raises venetoclax levels and fluid restriction worsens tumor lysis; hydration is protective.
Option D: Option D is incorrect because a single high dose without monitoring abandons the ramp-up and surveillance that prevent tumor lysis.
Option E: Option E is incorrect because the therapeutic goal is tumor cell death; the strategy controls its rate rather than preventing it.

12. [CASE 3 — QUESTION 4] Continuing with the same patient. During venetoclax therapy she develops neutropenia and her team wishes to add posaconazole, a strong CYP3A4 inhibitor, for antifungal prophylaxis. CYP3A4 is the principal enzyme that clears venetoclax. What is the correct management of the venetoclax dose?

A) Substantially reduce the venetoclax dose, because the strong CYP3A4 inhibitor markedly increases venetoclax exposure
B) Increase the venetoclax dose, because the antifungal accelerates its clearance
C) Make no change, because azole antifungals do not interact with venetoclax
D) Stop venetoclax permanently, because the combination is absolutely contraindicated in all circumstances
E) Replace venetoclax with a proteasome inhibitor to avoid the interaction

ANSWER: A

Rationale:

Because venetoclax is cleared by CYP3A4, a strong inhibitor such as posaconazole sharply raises venetoclax exposure, increasing toxicity and tumor lysis risk; the established management is a substantial venetoclax dose reduction when the strong inhibitor is co-administered, with particular caution during the ramp-up phase. The correct choice reflects this.

Option B: Option B is incorrect because an inhibitor slows clearance and raises levels rather than accelerating clearance.
Option C: Option C is incorrect because azole antifungals interact strongly with venetoclax through CYP3A4.
Option D: Option D is incorrect because the combination is managed by dose reduction rather than absolute prohibition, since antifungals are frequently needed in these patients.
Option E: Option E is incorrect because a proteasome inhibitor does not treat this disease and switching is not how the interaction is handled.

13. [CASE 4 — QUESTION 1] A 64-year-old man with newly diagnosed multiple myeloma is to begin a regimen of bortezomib (a proteasome inhibitor), lenalidomide (an immunomodulatory drug), and dexamethasone. Regarding bortezomib administration and class-based infection prophylaxis, which plan is correct?

A) Give bortezomib intravenously and provide no antiviral prophylaxis, since neither route nor infection is a concern
B) Give bortezomib intravenously at a higher dose to shorten the course, with no prophylaxis
C) Give bortezomib orally, since the oral route eliminates neuropathy
D) Give bortezomib subcutaneously to reduce the risk of peripheral neuropathy at equivalent systemic exposure, and provide antiviral prophylaxis (acyclovir or valacyclovir) against herpes zoster reactivation throughout therapy
E) Withhold antiviral prophylaxis and rely on vaccination alone during proteasome inhibitor therapy

ANSWER: D

Rationale:

Subcutaneous bortezomib markedly reduces peripheral neuropathy at systemic exposure equivalent to the intravenous route, making it the preferred route, and proteasome inhibitors as a class require antiviral prophylaxis against herpes zoster reactivation throughout therapy. The correct choice combines the subcutaneous route with the antiviral prophylaxis.

Option A: Option A is incorrect because the route strongly affects neuropathy and antiviral prophylaxis is required.
Option B: Option B is incorrect because raising the intravenous dose worsens neuropathy and omits needed prophylaxis.
Option C: Option C is incorrect because bortezomib has no oral formulation; the oral proteasome inhibitor is a different agent.
Option E: Option E is incorrect because pharmacologic antiviral prophylaxis is required during proteasome inhibitor therapy rather than relying on vaccination alone.

14. [CASE 4 — QUESTION 2] Continuing with the same patient. Three weeks into therapy he develops unilateral leg swelling, and Doppler ultrasound confirms a proximal deep vein thrombosis. He is receiving lenalidomide with high-dose dexamethasone. What is the most appropriate management?

A) Discontinue lenalidomide permanently and give no anticoagulation, attributing the clot to the cancer alone
B) Recognize venous thromboembolism as an expected complication of immunomodulatory-drug regimens amplified by dexamethasone; initiate therapeutic anticoagulation (low-molecular-weight heparin or a direct oral anticoagulant); and do not discontinue lenalidomide without oncology consultation
C) Treat the clot with aspirin alone as definitive therapy
D) Reassure the patient that leg swelling is expected and requires no treatment
E) Increase the dexamethasone dose to reduce the swelling

ANSWER: B

Rationale:

Venous thromboembolism is an expected complication of immunomodulatory-drug regimens, with risk amplified by concurrent dexamethasone. An established proximal deep vein thrombosis requires therapeutic anticoagulation with low-molecular-weight heparin or a direct oral anticoagulant, and the lenalidomide-containing regimen should not be discontinued without oncology consultation. The correct choice combines recognition, therapeutic anticoagulation, and appropriate continuation.

Option A: Option A is incorrect because an established clot requires anticoagulation, and abrupt discontinuation of lenalidomide is not done without oncology input.
Option C: Option C is incorrect because aspirin is prophylactic, not definitive treatment for an established thrombosis.
Option D: Option D is incorrect because a confirmed deep vein thrombosis is not benign and requires treatment.
Option E: Option E is incorrect because dexamethasone increases thrombotic risk and does not treat the clot.

15. [CASE 4 — QUESTION 3] Continuing with the same patient. He is receiving bortezomib intravenously on a twice-weekly schedule and develops a painful, distal, symmetric sensory neuropathy that limits his daily activities. What combination of measures best addresses this toxicity?

A) Discontinue all proteasome inhibitor therapy permanently and switch to an unrelated cytotoxic regimen
B) Continue intravenous twice-weekly dosing unchanged, since route and schedule do not affect neuropathy
C) Increase the bortezomib dose to push through the toxicity
D) Add a second proteasome inhibitor to share the dose and lessen the neuropathy
E) Switch from intravenous to subcutaneous administration, reduce the dose or move to a weekly schedule according to neuropathy grade, and add duloxetine, which has evidence for painful chemotherapy-induced peripheral neuropathy

ANSWER: E

Rationale:

Bortezomib peripheral neuropathy is its dose-limiting, cumulative toxicity. Subcutaneous administration lowers neuropathy at equivalent exposure, dose reduction or a switch to weekly dosing is guided by neuropathy grade, and duloxetine has Level I evidence for painful chemotherapy-induced peripheral neuropathy. The correct choice combines these measures.

Option A: Option A is incorrect because therapy can usually continue with route and dose modification rather than permanent discontinuation.
Option B: Option B is incorrect because route and schedule strongly influence neuropathy.
Option C: Option C is incorrect because increasing the dose worsens cumulative neurotoxicity.
Option D: Option D is incorrect because adding a second proteasome inhibitor adds toxicity rather than sparing the nerves.

16. [CASE 4 — QUESTION 4] Continuing with the same patient. His myeloma relapses after bortezomib, and carfilzomib (a second-generation proteasome inhibitor) is considered for a deeper response. Given carfilzomib's distinguishing safety profile, which assessment-and-management statement is correct?

A) Carfilzomib causes even more peripheral neuropathy than bortezomib and is a poor choice after bortezomib
B) Carfilzomib requires no baseline assessment and may be used regardless of cardiac history
C) Carfilzomib can provide deeper responses and tends to cause less peripheral neuropathy than bortezomib, but because its distinguishing toxicity is cardiovascular, obtain baseline cardiac assessment, exclude patients with advanced (New York Heart Association class III or IV) heart failure, and use careful hydration around infusions
D) Carfilzomib is interchangeable with bortezomib in route and toxicity, so the switch changes nothing
E) Carfilzomib should be avoided in all patients because it offers no efficacy advantage over bortezomib

ANSWER: C

Rationale:

Carfilzomib can yield deeper responses in relapsed disease and, by its mechanism of irreversible inhibition, tends to cause less peripheral neuropathy than bortezomib, but its distinguishing toxicity is cardiovascular — cardiomyopathy, heart failure, and hypertension — so baseline cardiac assessment, exclusion of advanced heart failure, and careful hydration around infusions are required. The correct choice combines the efficacy and neuropathy rationale with the cardiac safeguards.

Option A: Option A is incorrect because carfilzomib causes less, not more, neuropathy than bortezomib.
Option B: Option B is incorrect because baseline cardiac assessment is required and cardiac history matters.
Option D: Option D is incorrect because the two agents differ in route, neuropathy profile, and cardiovascular risk, so the switch is meaningful.
Option E: Option E is incorrect because carfilzomib does offer an efficacy advantage in the relapsed setting.

17. [CASE 5 — QUESTION 1] A 48-year-old man is newly diagnosed with acute myeloid leukemia, and molecular testing shows a FLT3 internal tandem duplication (FLT3-ITD; FLT3 is a receptor tyrosine kinase mutated in about a third of acute myeloid leukemias and conferring poor prognosis). He is fit for intensive therapy. Which targeted approach is most appropriate?

A) Add midostaurin, a multi-kinase inhibitor with FLT3 activity, to standard daunorubicin-cytarabine induction chemotherapy, which improves overall survival in newly diagnosed FLT3-mutant disease
B) Give gilteritinib as monotherapy, since it is the standard for newly diagnosed FLT3-mutant disease
C) Withhold all FLT3-directed therapy, since FLT3 mutations have no treatment implications
D) Treat with a BRAF inhibitor, since FLT3-ITD responds to BRAF blockade
E) Use venetoclax monotherapy, since it specifically targets FLT3

ANSWER: A

Rationale:

Midostaurin is a multi-kinase inhibitor with FLT3 activity approved for newly diagnosed FLT3-mutant acute myeloid leukemia in combination with standard daunorubicin-cytarabine induction chemotherapy, where it improves overall survival. The correct choice states this.

Option B: Option B is incorrect because gilteritinib's defined role is in relapsed or refractory FLT3-mutant disease, not as frontline monotherapy.
Option C: Option C is incorrect because FLT3-ITD is a defined pharmacogenomic target with FLT3 inhibitor therapy available.
Option D: Option D is incorrect because BRAF inhibitors target BRAF V600E, not FLT3.
Option E: Option E is incorrect because venetoclax targets BCL-2, not FLT3, and is not a FLT3-directed monotherapy.

18. [CASE 5 — QUESTION 2] Continuing with the same patient. During induction he requires posaconazole, a strong CYP3A4 inhibitor, for antifungal prophylaxis. Midostaurin is metabolized by CYP3A4 to active metabolites. What is the expected interaction and appropriate response?

A) Posaconazole accelerates midostaurin clearance, so the midostaurin dose should be doubled
B) Posaconazole has no effect on midostaurin, because midostaurin is renally cleared unchanged
C) Posaconazole converts midostaurin into an inactive compound, eliminating its efficacy
D) Posaconazole, as a strong CYP3A4 inhibitor, increases midostaurin exposure, so monitor closely for increased toxicity while continuing necessary antifungal prophylaxis
E) Posaconazole must never be combined with midostaurin under any circumstances, so antifungal prophylaxis should be omitted

ANSWER: D

Rationale:

Midostaurin is metabolized by CYP3A4, so a strong CYP3A4 inhibitor such as posaconazole — commonly used for antifungal prophylaxis in acute myeloid leukemia — increases midostaurin exposure and requires close monitoring for increased toxicity, while the needed prophylaxis is continued. The correct choice states the interaction and the monitoring-based response.

Option A: Option A is incorrect because an inhibitor slows clearance and raises exposure rather than accelerating clearance.
Option B: Option B is incorrect because midostaurin is metabolized by CYP3A4, not renally cleared unchanged, so the interaction is significant.
Option C: Option C is incorrect because the interaction raises active drug exposure rather than inactivating midostaurin.
Option E: Option E is incorrect because the combination is managed with monitoring rather than omitting essential antifungal prophylaxis.

19. [CASE 5 — QUESTION 3] Continuing with the same patient. He achieves remission but later relapses. Repeat molecular testing now shows an IDH2 mutation (IDH2 is a mutated metabolic enzyme producing an oncometabolite that blocks myeloid differentiation). Which targeted agent matches this finding, and what testing governs its use?

A) Ivosidenib, which targets IDH2 and requires IDH1 mutation testing
B) Enasidenib, which targets IDH2 and is used after confirming an IDH2 mutation; it acts by restoring differentiation of leukemic blasts rather than by direct cytotoxicity
C) Midostaurin, because IDH2 mutations respond specifically to FLT3 inhibition
D) Olaparib, because IDH2-mutant leukemia is treated with PARP inhibition
E) Venetoclax monotherapy, because it directly targets the IDH2 enzyme

ANSWER: B

Rationale:

Enasidenib is the IDH2 inhibitor and is used after confirming an IDH2 mutation; like other IDH inhibitors it works by suppressing the oncometabolite and restoring differentiation of leukemic blasts rather than by direct cytotoxicity. The correct choice matches the agent to the mutation and states its mechanism.

Option A: Option A is incorrect because ivosidenib targets IDH1 (requiring IDH1 testing), not IDH2.
Option C: Option C is incorrect because midostaurin targets FLT3, not IDH2.
Option D: Option D is incorrect because olaparib is a PARP inhibitor used for homologous-recombination-deficient solid tumors, not IDH2-mutant leukemia.
Option E: Option E is incorrect because venetoclax targets BCL-2, not the IDH2 enzyme.

20. [CASE 5 — QUESTION 4] Continuing with the same patient. Six weeks after starting enasidenib he develops progressive dyspnea, fever, and bilateral pulmonary infiltrates with peripheral edema; blood cultures are pending. A covering clinician is preparing to treat this solely as community-acquired pneumonia. What is the most appropriate immediate management?

A) Treat solely as bacterial pneumonia with antibiotics, withholding corticosteroids and continuing enasidenib without further thought
B) Diagnose acute heart failure, give diuresis alone, and discontinue enasidenib permanently
C) Treat as anaphylaxis with epinephrine and antihistamines, avoiding corticosteroids
D) Attribute the picture to tumor lysis syndrome and give only a uric-acid-lowering agent
E) Recognize likely differentiation syndrome given the agent and timing; start systemic corticosteroids (dexamethasone) promptly while concurrently evaluating for infection, and continue enasidenib unless manifestations are severe

ANSWER: E

Rationale:

IDH inhibitors force leukemic blasts to mature, and differentiation syndrome — dyspnea, fever, pulmonary infiltrates, and edema within the first weeks — is the characteristic, potentially fatal complication frequently mistaken for pneumonia. Prompt systemic corticosteroids are started without waiting for confirmation because delayed treatment raises mortality, with concurrent evaluation for infection and continuation of the drug unless manifestations are severe. The correct choice captures this.

Option A: Option A is incorrect because anchoring on pneumonia and withholding corticosteroids risks fatal undertreatment of differentiation syndrome.
Option B: Option B is incorrect because the presentation is not simple heart failure, and diuresis alone with permanent discontinuation is not the management.
Option C: Option C is incorrect because this is an inflammatory consequence of forced maturation, not anaphylaxis, and corticosteroids are essential.
Option D: Option D is incorrect because the pulmonary infiltrates and timing point to differentiation syndrome rather than tumor lysis, which a uric-acid-lowering agent would not address.

21. [CASE 6 — QUESTION 1] A 60-year-old woman with high-grade serous ovarian cancer responds to platinum-based chemotherapy. Her tumor carries a BRCA1 mutation (BRCA genes run the homologous-recombination back-up system for repairing DNA double-strand breaks). A PARP inhibitor is being considered. What is the mechanistic rationale, and what testing guides selection?

A) PARP inhibitors directly cut tumor DNA, so they are used regardless of BRCA or homologous-recombination status
B) PARP inhibitors restore BRCA function, so they are reserved for tumors with intact homologous recombination
C) PARP inhibitors exploit synthetic lethality — a BRCA-mutant tumor has already lost its homologous-recombination back-up repair, so blocking PARP leaves it unable to repair DNA and it dies selectively; BRCA and homologous-recombination-deficiency testing guides selection
D) PARP inhibitors act only on tumors with no mutations at all, so testing is used to exclude any mutation
E) PARP inhibitors are selected by HER2 status, since PARP inhibition requires HER2 amplification

ANSWER: C

Rationale:

PARP inhibitors exploit synthetic lethality: a BRCA-mutant tumor has already lost its homologous-recombination back-up repair pathway and survives by relying on PARP-mediated repair, so blocking PARP leaves it unable to fix accumulating DNA damage and it dies selectively, while normal cells with intact repair are spared. BRCA and homologous-recombination-deficiency testing guides patient selection. The correct choice states both the mechanism and the testing.

Option A: Option A is incorrect because PARP inhibitors prevent repair of breaks rather than cutting DNA, and benefit depends on repair status.
Option B: Option B is incorrect because the drugs do not restore BRCA function — selectivity arises when that function is absent.
Option D: Option D is incorrect because the drugs exploit a repair-deficient state rather than requiring a mutation-free tumor.
Option E: Option E is incorrect because PARP inhibitor selection depends on BRCA/homologous-recombination status, not HER2.

22. [CASE 6 — QUESTION 2] Continuing with the same patient. She begins niraparib (a PARP inhibitor) as maintenance therapy. Three weeks in, routine monitoring shows a platelet count consistent with grade 3 thrombocytopenia; she has no active bleeding. What is the most appropriate management?

A) Recognize niraparib's characteristic thrombocytopenia, hold the drug and resume at a reduced dose once platelets recover, and continue the weekly blood-count monitoring that is standard during the first month of niraparib therapy
B) Continue niraparib at full dose, since PARP inhibitors do not cause thrombocytopenia
C) Permanently discontinue all PARP inhibitor therapy and transfuse platelets regardless of bleeding
D) Diagnose tumor lysis syndrome and begin a uric-acid-lowering agent
E) Attribute the low platelets to prior platinum chemotherapy alone and take no niraparib-specific action

ANSWER: A

Rationale:

Niraparib is distinguished among PARP inhibitors by a high rate of hematologic toxicity, particularly thrombocytopenia, which is why weekly blood-count monitoring is standard during the first month. Grade 3 thrombocytopenia is managed by holding niraparib and resuming at a reduced dose once platelets recover, with continued monitoring. The correct choice captures the recognition and the dose-and-monitoring response.

Option B: Option B is incorrect because niraparib clearly does cause thrombocytopenia.
Option C: Option C is incorrect because the standard response is dose interruption and reduction, not permanent discontinuation with prophylactic transfusion absent bleeding.
Option D: Option D is incorrect because isolated thrombocytopenia here reflects niraparib toxicity, not tumor lysis syndrome.
Option E: Option E is incorrect because the appropriate action is niraparib-specific dose modification and continued monitoring rather than no action.

23. [CASE 6 — QUESTION 3] Continuing with the same patient. She is also taking several medications metabolized by CYP3A4, and her team weighs niraparib against olaparib partly on drug-interaction grounds. How do these two PARP inhibitors differ in metabolism, and what does this imply?

A) Both are metabolized chiefly by CYP3A4, so neither offers any drug-interaction advantage
B) Olaparib is metabolized by carboxylesterases and niraparib by CYP3A4, so olaparib has fewer CYP interactions
C) Both are metabolized by carboxylesterases, so strong CYP3A4 inhibitors raise the levels of each substantially
D) Niraparib is metabolized by CYP3A4 and is therefore the better choice when many CYP3A4 substrates are co-administered
E) Niraparib is metabolized predominantly by carboxylesterases rather than CYP3A4, giving it fewer CYP-based drug interactions, whereas olaparib is metabolized primarily by CYP3A4 and is more affected by strong CYP3A4 inhibitors

ANSWER: E

Rationale:

Niraparib is metabolized predominantly by carboxylesterases rather than CYP3A4, so it has fewer CYP-based drug interactions, whereas olaparib is metabolized primarily by CYP3A4 and its exposure rises with strong CYP3A4 inhibitors, prompting dose reduction. In a patient on multiple CYP3A4 substrates, niraparib's metabolic route is advantageous. The correct choice states this difference and its implication.

Option A: Option A is incorrect because the two differ in metabolism, and niraparib's carboxylesterase route does confer an interaction advantage.
Option B: Option B is incorrect because it reverses the two drugs.
Option C: Option C is incorrect because only niraparib is chiefly carboxylesterase-metabolized; olaparib is a CYP3A4 substrate.
Option D: Option D is incorrect because niraparib is not chiefly CYP3A4-metabolized — that description fits olaparib.

24. [CASE 6 — QUESTION 4] Continuing with the same patient. She is scheduled for major abdominal surgery while on niraparib, and the surgical team is also coordinating care for two other oncology patients — one on a BTK inhibitor and one on an immunomodulatory drug. Integrating the distinct perioperative reasons each agent is held, which statement is correct?

A) None of these three agents needs to be held before surgery, since none affects bleeding, clotting, or wound healing
B) The PARP inhibitor is held because impaired DNA repair can affect surgical wound healing; the BTK inhibitor is held because it causes platelet dysfunction and bleeding risk; and the immunomodulatory drug is held because surgical immobility compounds its venous thromboembolism risk
C) All three are held for the identical reason of QTc prolongation
D) Only the PARP inhibitor must be held, and solely because of QTc prolongation
E) All three are held because they are proteasome inhibitors requiring cardiac clearance

ANSWER: B

Rationale:

Each agent is held perioperatively for a distinct mechanistic reason: a PARP inhibitor because its interference with DNA repair can impair surgical wound healing; a BTK inhibitor because it causes platelet dysfunction and bleeding risk; and an immunomodulatory drug because surgical immobility compounds its venous thromboembolism risk. The correct choice attributes each hold to its correct mechanism.

Option A: Option A is incorrect because each agent carries a specific perioperative concern.
Option C: Option C is incorrect because the three are held for different reasons, not a shared QTc effect.
Option D: Option D is incorrect because all three require attention, and the PARP inhibitor's reason is impaired DNA repair and wound healing, not QTc.
Option E: Option E is incorrect because these agents are not all proteasome inhibitors and the holds are not for a common cardiac clearance.