Chapter 34 — Anti-Cancer Drugs Part II — Module 2 — Targeted Small Molecule Inhibitors: Clinical Vignette
1. A 61-year-old postmenopausal woman with estrogen-receptor-positive, HER2-negative metastatic breast cancer is on 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 repeat the ECG in three months, since she is asymptomatic
B) Permanently discontinue all CDK4/6 inhibitor therapy and switch immediately to cytotoxic chemotherapy
C) Continue ribociclib and add a fluoroquinolone-based regimen empirically
D) Hold ribociclib because the QTc exceeds the interruption threshold, review and remove concurrent QTc-prolonging medications, correct any electrolyte abnormalities, and resume at a reduced dose once the QTc recovers, not restarting if the QTc recurrently exceeds 500 ms
E) Increase the ribociclib dose to achieve faster disease control before the QTc worsens
ANSWER: D
Rationale:
Ribociclib is the CDK4/6 inhibitor with the most stringent QTc monitoring protocol. A QTc above roughly 480 ms requires interruption, so a value of 495 ms mandates holding the drug, removing concurrent QTc-prolonging agents, correcting electrolytes, and resuming at a reduced dose after recovery; recurrent QTc above 500 ms requires permanent discontinuation. 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 ignored 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 at first threshold breach.
Option C: Option C is incorrect because adding a fluoroquinolone introduces another QTc-prolonging drug, compounding the risk.
Option E: Option E is incorrect because increasing the dose would worsen QTc prolongation.
2. A 54-year-old man with BRAF V600E-mutant metastatic melanoma has been on single-agent vemurafenib (a BRAF inhibitor) for two months. He presents with a new, firm, rapidly enlarging keratotic nodule on his forearm. What is the most appropriate management?
A) Reassure him that new skin lesions are expected and benign; take no action
B) Biopsy the lesion to evaluate for cutaneous squamous-cell carcinoma or keratoacanthoma, and add a MEK inhibitor to suppress the paradoxical MAPK pathway activation driving these lesions
C) Stop all BRAF-directed therapy permanently and treat the nodule as metastatic melanoma
D) Begin systemic antibiotics for a presumed cutaneous infection and continue vemurafenib unchanged
E) Initiate high-dose systemic corticosteroids for a presumed drug hypersensitivity reaction
ANSWER: B
Rationale:
BRAF inhibitor monotherapy paradoxically activates the MAPK growth 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 A: Option A is incorrect because a new rapidly enlarging nodule warrants biopsy rather than reassurance alone.
Option C: Option C is incorrect because the lesion reflects paradoxical activation in normal skin, not melanoma metastasis, and BRAF-directed therapy is intensified rather than abandoned.
Option D: Option D is incorrect because this is a neoplastic lesion, not an infection, 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. A 70-year-old woman with chronic lymphocytic leukemia on ibrutinib (a first-generation BTK inhibitor) develops new atrial fibrillation with a CHA2DS2-VASc score (a validated stroke-risk score) high enough to warrant anticoagulation. How should anticoagulation be managed?
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 a more selective BTK inhibitor such as acalabrutinib or zanubrutinib
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 both the 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 score does warrant anticoagulation; the task is choosing it safely.
Option D: Option D is incorrect because warfarin is the agent to avoid, and proceeding without INR monitoring would be dangerous.
4. A 66-year-old man with IDH2-mutant acute myeloid leukemia started enasidenib (an IDH2 inhibitor) six weeks ago. He presents with progressive dyspnea, fever, and bilateral pulmonary infiltrates on chest imaging, with peripheral edema. Blood cultures are pending. What is the most appropriate immediate management?
A) Recognize likely differentiation syndrome given the agent and timing, and start systemic corticosteroids (dexamethasone) promptly while concurrently evaluating for infection; continue enasidenib unless manifestations are severe
B) Withhold corticosteroids until blood cultures finalize, treating the presentation solely as bacterial pneumonia
C) Diagnose acute heart failure and treat with diuresis alone, discontinuing enasidenib permanently
D) Treat as an anaphylactic reaction with epinephrine and antihistamines, avoiding corticosteroids
E) Attribute the picture to tumor lysis syndrome and give only a uric-acid-lowering agent
ANSWER: A
Rationale:
IDH inhibitors force leukemic blasts to mature, and differentiation syndrome — dyspnea, fever, pulmonary infiltrates, and edema within the first weeks of therapy — is the characteristic, potentially fatal complication that is frequently mistaken for pneumonia. Prompt systemic corticosteroids (dexamethasone) 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 B: Option B is incorrect because withholding corticosteroids to await cultures risks fatal undertreatment of differentiation syndrome.
Option C: Option C is incorrect because the presentation is not simple heart failure, and diuresis alone with permanent discontinuation is not the management.
Option D: Option D is incorrect because this is an inflammatory consequence of forced maturation, not anaphylaxis, and corticosteroids are essential.
Option E: Option E 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.
5. A 68-year-old man with chronic lymphocytic leukemia and bulky lymphadenopathy is about to begin venetoclax (a BCL-2 inhibitor). Given his high tumor burden, which management plan most appropriately addresses the principal early risk of this drug?
A) Start at the full target dose to clear the disease rapidly and monitor laboratory values weekly
B) Begin venetoclax with a strong CYP3A4 inhibitor for antifungal coverage and restrict fluids
C) Use the mandatory stepwise dose ramp-up, withhold strong CYP3A4 inhibitors during ramp-up, and provide allopurinol prophylaxis, aggressive hydration, and laboratory monitoring 6 to 8 hours after each dose increase to manage tumor lysis syndrome risk
D) Give a single high loading dose followed by observation without laboratory monitoring
E) Premedicate with a drug that prevents tumor cell death to avoid any metabolic effect
ANSWER: C
Rationale:
Venetoclax triggers rapid, synchronous death of BCL-2-dependent tumor cells, and in a high-burden patient this creates a substantial early risk of tumor lysis syndrome. The standard mitigation is a mandatory stepwise dose ramp-up, withholding strong CYP3A4 inhibitors during ramp-up (they raise venetoclax exposure when tumor lysis risk is highest), 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 starting at the full dose maximizes the simultaneous cell death that drives 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 with no 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 is to control its rate, not prevent it.
6. A 59-year-old woman with newly diagnosed multiple myeloma is receiving lenalidomide, bortezomib, and dexamethasone. Three weeks into therapy she develops unilateral leg swelling and calf tenderness, and a D-dimer is markedly elevated. Doppler ultrasound confirms a proximal deep vein thrombosis. What is the most appropriate management?
A) Discontinue lenalidomide permanently and start no anticoagulation, attributing the event to the cancer alone
B) Reassure the patient that leg swelling is expected and requires no treatment
C) Begin antiplatelet therapy with aspirin alone as definitive treatment for the established clot
D) Recognize venous thromboembolism as an expected complication of immunomodulatory-drug regimens, initiate therapeutic anticoagulation (low-molecular-weight heparin or a direct oral anticoagulant), and do not discontinue lenalidomide without oncology consultation
E) Increase the dexamethasone dose to reduce the leg swelling
ANSWER: D
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, since it is central to disease control. The correct choice combines recognition with therapeutic anticoagulation and appropriate continuation of therapy.
Option A: Option A is incorrect because an established clot requires anticoagulation and abrupt unilateral discontinuation of lenalidomide is not made without oncology input.
Option B: Option B is incorrect because a confirmed deep vein thrombosis is not benign leg swelling and requires treatment.
Option C: Option C is incorrect because aspirin is a prophylactic measure, not definitive treatment for an established thrombosis.
Option E: Option E is incorrect because dexamethasone increases thrombotic risk and does not treat the clot.
7. A 63-year-old woman with PIK3CA-mutant, estrogen-receptor-positive, HER2-negative metastatic breast cancer on alpelisib (a PI3K-alpha inhibitor) plus fulvestrant has a routine fasting glucose of 320 mg/dL at the start of her second cycle. She has mild symptoms of hyperglycemia but no ketoacidosis. What is the most appropriate management?
A) Stop alpelisib permanently, since hyperglycemia is an absolute contraindication to continued therapy
B) 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 dose interruption only for very severe or refractory hyperglycemia
C) Attribute the glucose to laboratory error and take no action
D) Begin high-dose corticosteroids to counteract the metabolic effect
E) Switch the patient to an mTOR inhibitor, which does not affect glucose
ANSWER: B
Rationale:
Alpelisib blocks PI3K-alpha, the isoform insulin uses for glucose uptake, so hyperglycemia from insulin resistance is its defining and common toxicity. Management is dietary modification plus pharmacologic therapy — metformin first, with insulin added as needed — alongside fasting glucose monitoring, while continuing alpelisib and interrupting only for very severe (for example, glucose persistently above roughly 500 mg/dL) or refractory hyperglycemia. The correct choice captures the mechanism and the stepwise management.
Option A: Option A is incorrect because hyperglycemia is managed rather than being an absolute contraindication at this level.
Option C: Option C is incorrect because a glucose of 320 mg/dL with symptoms is a real, expected drug effect requiring treatment.
Option D: Option D 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 and would abandon an effective therapy.
8. A 64-year-old man with relapsed multiple myeloma receiving carfilzomib (a second-generation proteasome inhibitor) develops new exertional dyspnea, orthopnea, and lower-extremity edema. Echocardiography shows a newly reduced left ventricular ejection fraction. What is the most appropriate management?
A) Attribute the findings to bortezomib-type peripheral neuropathy and reduce the dose for neuropathy
B) Continue carfilzomib at full dose, since it has no cardiac effects
C) Diagnose differentiation syndrome and start a uric-acid-lowering agent
D) Increase the carfilzomib infusion rate to improve disease control
E) Recognize carfilzomib-associated cardiac toxicity, hold the drug for this grade 3 or higher cardiac event, obtain cardiac evaluation, and manage the heart failure, resuming only after recovery and with careful hydration if treatment continues
ANSWER: E
Rationale:
Carfilzomib is distinguished among proteasome inhibitors by cardiovascular toxicity, including cardiomyopathy and heart failure. New dyspnea, orthopnea, edema, and a reduced ejection fraction represent a significant cardiac event, so the drug is held, cardiac evaluation is obtained, and heart failure is managed; resumption occurs only after recovery and with careful hydration if therapy continues. The correct choice captures this recognition and management.
Option A: Option A is incorrect because the picture is cardiac failure, not the sensory neuropathy characteristic of bortezomib.
Option B: Option B is incorrect because carfilzomib does have prominent cardiac toxicity.
Option C: Option C is incorrect because differentiation syndrome is a complication of IDH inhibitors, not carfilzomib, and a uric-acid-lowering agent does not treat heart failure.
Option D: Option D is incorrect because increasing the infusion would worsen the cardiac toxicity.
9. A 72-year-old woman with relapsed chronic lymphocytic leukemia on idelalisib (a PI3K-delta inhibitor) develops grade 3 elevation of her transaminases (markedly increased liver enzymes) together with several weeks of worsening watery diarrhea. What is the most appropriate management?
A) Recognize idelalisib-associated immune-mediated hepatotoxicity and colitis; interrupt the drug, initiate corticosteroids for the immune-mediated toxicity, and confirm that Pneumocystis prophylaxis is in place given the infection risk
B) Continue idelalisib unchanged and treat the diarrhea with loperamide alone, ignoring the liver enzymes
C) Attribute the transaminitis to disease progression and increase the idelalisib dose
D) Diagnose tumor lysis syndrome and treat with a uric-acid-lowering agent
E) Treat the presentation as anaphylaxis with epinephrine and avoid corticosteroids
ANSWER: A
Rationale:
Idelalisib produces immune-mediated toxicities — hepatotoxicity with transaminase elevation and an inflammatory colitis resembling inflammatory bowel disease — because PI3K-delta is central to normal immune signaling; grade 3 hepatotoxicity and significant colitis call for drug interruption and corticosteroids, and Pneumocystis prophylaxis must be ensured given the elevated opportunistic infection risk. The correct choice captures this.
Option B: Option B is incorrect because grade 3 transaminitis cannot be ignored and the colitis is immune-mediated, not adequately addressed by loperamide alone.
Option C: Option C is incorrect because the transaminitis reflects immune-mediated hepatotoxicity, not progression, and increasing the dose would worsen it.
Option D: Option D is incorrect because this picture is immune-mediated organ toxicity, not tumor lysis syndrome.
Option E: Option E is incorrect because this is not anaphylaxis, and corticosteroids are in fact a key part of management.
10. A 67-year-old woman with multiple myeloma receiving intravenous bortezomib (a proteasome inhibitor) on a twice-weekly schedule develops a painful, distal, symmetric sensory neuropathy limiting her daily activities. What is the most appropriate management?
A) Discontinue all proteasome inhibitor therapy permanently and switch to an unrelated cytotoxic regimen
B) Continue intravenous twice-weekly dosing unchanged, since the route and schedule do not influence neuropathy
C) Switch from intravenous to subcutaneous administration to reduce neuropathy, 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
D) Increase the bortezomib dose to push through the toxicity
E) Add a second proteasome inhibitor to share the dose and lessen the neuropathy
ANSWER: C
Rationale:
Bortezomib peripheral neuropathy is its dose-limiting, cumulative toxicity, and several measures reduce it: subcutaneous administration markedly 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.
Option A: Option A is incorrect because therapy can usually be continued with route and dose modification rather than permanent discontinuation.
Option B: Option B is incorrect because route and schedule strongly influence neuropathy — the subcutaneous route and weekly dosing reduce it.
Option D: Option D is incorrect because increasing the dose worsens cumulative neurotoxicity.
Option E: Option E is incorrect because adding a second proteasome inhibitor adds toxicity rather than sparing the nerves.
11. A 58-year-old woman on niraparib (a PARP inhibitor) as maintenance therapy after platinum-responsive ovarian cancer is found three weeks into treatment to have a platelet count consistent with grade 3 thrombocytopenia on routine monitoring. She has no active bleeding. What is the most appropriate management?
A) Continue niraparib at full dose, since PARP inhibitors do not cause thrombocytopenia
B) 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
C) Permanently discontinue all PARP inhibitor therapy and transfuse platelets prophylactically regardless of bleeding
D) Diagnose tumor lysis syndrome and begin a uric-acid-lowering agent
E) Attribute the low platelets to the prior platinum chemotherapy alone and take no action specific to niraparib
ANSWER: B
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 A: Option A 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 in the absence of 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, although prior platinum can affect counts, the appropriate action is niraparib-specific dose modification and continued monitoring rather than no action.
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