Chapter 33 — Anti-Cancer Drugs Part I: Pharmacology — Module 4 — Topoisomerase Inhibitors and Antitumor Antibiotics
1. A 58-year-old woman with metastatic colorectal cancer is receiving her first cycle of FOLFIRI (which includes irinotecan). About 20 minutes into the irinotecan infusion she develops crampy abdominal pain, diaphoresis, lacrimation, rhinorrhea, and the sudden onset of watery diarrhea. Her vital signs are stable. What is the most appropriate immediate intervention?
A) Start high-dose loperamide and send her home with instructions
B) Stop chemotherapy permanently and label irinotecan as a drug allergy
C) Administer atropine, because this is the early cholinergic syndrome caused by irinotecan-mediated acetylcholinesterase inhibition
D) Begin empiric oral vancomycin for Clostridioides difficile colitis
E) Give a stimulant laxative to clear the offending metabolite
ANSWER: C
Rationale:
The timing (during the infusion) and the cholinergic constellation (cramping, diaphoresis, lacrimation, rhinorrhea, early diarrhea) identify the early cholinergic syndrome, which results from irinotecan inhibition of acetylcholinesterase; the correct immediate treatment is atropine, and prophylactic atropine can be considered for subsequent cycles.
Option A: Option A is incorrect because loperamide treats the late mucosal-injury diarrhea, not the early cholinergic syndrome, and sending her home mid-reaction is unsafe.
Option B: Option B is incorrect because this is a predictable, treatable pharmacologic effect, not an allergy mandating permanent discontinuation.
Option D: Option D is incorrect because the presentation is a drug-induced cholinergic effect, not an infection, so vancomycin is inappropriate.
Option E: Option E is incorrect because a stimulant laxative would worsen the diarrhea and does not address the cholinergic mechanism that atropine targets.
2. A 64-year-old man calls four days after an irinotecan infusion reporting more than ten watery stools per day for the past 24 hours despite taking loperamide at home, plus a temperature of 38.6 degrees Celsius and lightheadedness. A same-day clinic check shows an absolute neutrophil count of 600 per microliter. What is the most appropriate management?
A) Admit for intravenous fluid resuscitation and empiric broad-spectrum antibiotics, because the combination of severe late diarrhea with febrile neutropenia is potentially life-threatening
B) Reassure him and advise continuing loperamide at home with oral fluids only
C) Administer atropine, since this delayed diarrhea is cholinergic
D) Stop loperamide and give a stimulant laxative to clear residual SN-38
E) Schedule a routine outpatient colonoscopy in two weeks and continue current management
ANSWER: A
Rationale:
Severe late irinotecan diarrhea combined with fever and neutropenia is a medical emergency: dehydration plus a compromised mucosal barrier and low neutrophil count create a high risk of bacterial translocation and sepsis, so the patient requires hospital admission for intravenous hydration and empiric broad-spectrum antibiotics.
Option B: Option B is incorrect because home oral management is inadequate and dangerous once febrile neutropenia and volume depletion are present.
Option C: Option C is incorrect because late diarrhea is mucosal (SN-38) rather than cholinergic, so atropine is not the treatment.
Option D: Option D is incorrect because a stimulant laxative would worsen fluid losses and is contraindicated in this setting.
Option E: Option E is incorrect because a routine delayed colonoscopy ignores the acute, potentially fatal combination of febrile neutropenia and severe diarrhea that demands immediate inpatient care.
3. A 52-year-old woman receiving doxorubicin-based chemotherapy for breast cancer has a surveillance echocardiogram showing her left ventricular ejection fraction (LVEF) has fallen from a baseline of 62% to 47%. She has mild exertional dyspnea. What is the most appropriate next step?
A) Continue doxorubicin at full dose, since a single low LVEF is not meaningful
B) Increase the doxorubicin dose to complete therapy faster before further decline
C) Switch to bleomycin, which has no cardiac toxicity
D) Hold the anthracycline, obtain cardiology (cardio-oncology) consultation, and initiate an ACE inhibitor (or angiotensin receptor blocker) and a beta-blocker, because a clinically significant LVEF decline below 50% signals anthracycline cardiotoxicity
E) Add dexrazoxane and continue doxorubicin unchanged with no other intervention
ANSWER: D
Rationale:
A drop in LVEF to below 50% with a clinically meaningful decline from baseline, accompanied by symptoms, indicates anthracycline-induced cardiac dysfunction; the appropriate response is to hold the anthracycline, obtain cardio-oncology input, and start guideline-directed heart failure therapy (an ACE inhibitor or angiotensin receptor blocker plus a beta-blocker) to limit progression.
Option A: Option A is incorrect because a significant symptomatic LVEF decline below 50% is clinically important and cannot be dismissed.
Option B: Option B is incorrect because increasing the dose would worsen cumulative cardiotoxicity in a patient already showing cardiac injury.
Option C: Option C is incorrect because bleomycin is not a substitute for doxorubicin's antitumor role and carries its own serious pulmonary toxicity; switching is not the management of cardiac decline.
Option E: Option E is incorrect because simply adding dexrazoxane while continuing full-dose doxorubicin ignores the need to hold therapy, involve cardiology, and start cardioprotective heart failure medications in a patient with established dysfunction.
4. A 30-year-old man with testicular germ cell tumor on BEP (bleomycin, etoposide, cisplatin) develops rising serum creatinine and a falling creatinine clearance over two cycles, attributed to cisplatin nephrotoxicity. Beyond adjusting cisplatin, why does the worsening renal function specifically heighten concern about bleomycin?
A) Bleomycin is hepatically cleared, so renal impairment has no effect on its levels
B) Bleomycin is eliminated renally, so declining renal function reduces its clearance, raises drug exposure, and increases the risk of bleomycin pulmonary toxicity, warranting dose and monitoring reassessment
C) Renal impairment converts bleomycin into a cardiotoxic metabolite
D) Bleomycin requires renal activation, so worse renal function makes it ineffective
E) Renal impairment only matters for etoposide and has no bearing on bleomycin
ANSWER: B
Rationale:
Bleomycin is eliminated predominantly by the kidneys, so a decline in renal function reduces its clearance, increases systemic exposure, and thereby raises the risk of its dose-limiting pulmonary toxicity; worsening renal function in a BEP patient should prompt reassessment of bleomycin dosing and intensified pulmonary monitoring (and is a recognized pulmonary-toxicity risk factor).
Option A: Option A is incorrect because bleomycin is renally, not hepatically, cleared, so renal function is highly relevant.
Option C: Option C is incorrect because renal impairment does not transform bleomycin into a cardiotoxic metabolite; the concern is accumulation and lung toxicity.
Option D: Option D is incorrect because bleomycin does not require renal activation; impaired renal function increases exposure rather than abolishing efficacy.
Option E: Option E is incorrect because, although etoposide also needs renal dose consideration, renal function very much affects bleomycin clearance and its pulmonary risk.
5. A 27-year-old man who completed bleomycin-containing chemotherapy five months ago undergoes an urgent operation under general anesthesia. The anesthesia team, unaware of his bleomycin history, maintains a high inspired oxygen fraction throughout the case. In the recovery period he develops rapidly progressive hypoxemia, diffuse bilateral infiltrates, and respiratory distress. What is the most likely explanation?
A) A pulmonary embolism from intraoperative immobility
B) Aspiration pneumonitis unrelated to his chemotherapy
C) Cisplatin-induced pulmonary edema from fluid administration
D) An anesthetic drug allergy producing bronchospasm
E) Bleomycin-related acute lung injury (an ARDS-like syndrome) triggered by exposure to a high inspired oxygen fraction in bleomycin-sensitized lung
ANSWER: E
Rationale:
Bleomycin sensitizes lung tissue such that high inspired oxygen concentrations can precipitate acute, severe lung injury resembling acute respiratory distress syndrome (ARDS); this man's recent bleomycin exposure plus intraoperative high inspired oxygen and subsequent rapidly progressive hypoxemia with bilateral infiltrates fits this potentially fatal interaction. The lesson reinforces keeping the inspired oxygen fraction as low as safely tolerable in any prior-bleomycin patient.
Option A: Option A is incorrect because, while embolism causes hypoxemia, it does not typically produce diffuse bilateral infiltrates in the setting of recent bleomycin plus high oxygen, which points to oxygen-triggered lung injury.
Option B: Option B is incorrect because the clinical context (bleomycin plus high inspired oxygen) specifically implicates the bleomycin-oxygen interaction rather than aspiration.
Option C: Option C is incorrect because cisplatin does not characteristically cause this oxygen-triggered diffuse lung injury; the mechanism here is bleomycin sensitization.
Option D: Option D is incorrect because an anesthetic allergy would more likely cause bronchospasm or anaphylaxis, not the diffuse infiltrative oxygen-related injury described.
6. An 80-year-old man with extensive-stage small cell lung cancer has a poor performance status and significant comorbidities that preclude intensive intravenous platinum-based combination therapy. His oncologist wants to use etoposide in a way that maximizes the chance of response given his frailty. Which approach is most rational?
A) A single large intravenous bolus of etoposide to minimize clinic visits
B) Withhold etoposide entirely because it cannot work without cisplatin
C) Use a prolonged, divided oral etoposide schedule over several days, exploiting the drug's schedule dependency to sustain exposure during the topoisomerase II-vulnerable window and improve response relative to bolus dosing
D) Give etoposide once every six weeks at very high dose
E) Replace etoposide with bleomycin, which is better tolerated in the elderly
ANSWER: C
Rationale:
Etoposide is schedule-dependent, so dividing the same total dose into prolonged lower-dose exposure sustains drug levels across more of the cell-cycle window in which topoisomerase II is active and yields higher response rates than an equivalent bolus; a prolonged oral schedule is therefore a rational, better-tolerated choice for a frail elderly patient who cannot receive intensive intravenous combinations.
Option A: Option A is incorrect because a single large bolus does not exploit etoposide's schedule dependency and is generally less effective than divided dosing.
Option B: Option B is incorrect because single-agent etoposide does have activity and is a legitimate option in patients unable to tolerate platinum doublets.
Option D: Option D is incorrect because infrequent very-high-dose administration is the opposite of the sustained-exposure approach that benefits etoposide.
Option E: Option E is incorrect because bleomycin is not an appropriate substitute for etoposide in small cell lung cancer and carries serious pulmonary toxicity, especially in the elderly.
7. A 67-year-old woman with recurrent ovarian cancer has responded to anthracycline therapy but has nearly reached the cumulative conventional doxorubicin dose associated with substantial cardiac risk. Her cardiac function remains acceptable, and continued anthracycline exposure is still desired. Which option best balances continued benefit against cardiac safety, and what should she be counseled about?
A) Switch to pegylated liposomal doxorubicin, which reduces cardiotoxicity and myelosuppression while introducing hand-foot syndrome (palmar-plantar erythrodysesthesia) as the main dose-limiting toxicity to counsel her about
B) Continue conventional doxorubicin past the cardiac ceiling because she is responding
C) Double the conventional doxorubicin dose to finish therapy before cardiac decline
D) Add bleomycin to the regimen to allow lower doxorubicin dosing
E) Stop all anticancer therapy permanently because the cardiac ceiling has been reached
ANSWER: A
Rationale:
Pegylated liposomal doxorubicin offers reduced cardiotoxicity and myelosuppression relative to conventional doxorubicin and is active in ovarian cancer, making it a rational way to continue anthracycline benefit near the conventional cardiac ceiling; the key counseling point is hand-foot syndrome, its characteristic dose-limiting toxicity, managed by dose reduction and cycle delay.
Option B: Option B is incorrect because continuing conventional doxorubicin past the cardiac ceiling courts irreversible cardiomyopathy.
Option C: Option C is incorrect because doubling the dose would accelerate cumulative cardiotoxicity, the opposite of a safe strategy.
Option D: Option D is incorrect because adding bleomycin (a pulmonary-toxic agent without a role here) does not address the cardiac-ceiling problem and introduces new risk.
Option E: Option E is incorrect because reaching the conventional doxorubicin ceiling does not require abandoning all therapy; liposomal doxorubicin or other active agents remain available.
8. A 4-year-old child is receiving actinomycin D (dactinomycin) as part of a regimen for Wilms tumor (a childhood kidney cancer). During a peripheral infusion, the nurse notes swelling, blanching, and the infusion slowing at the catheter site, raising concern for extravasation (leakage of the drug out of the vein into surrounding tissue). Considering the properties of actinomycin D, what is the correct understanding and action?
A) Actinomycin D is non-irritant, so the infusion can simply be continued at the same site
B) Extravasation of actinomycin D is harmless because it is rapidly cleared from tissue
C) The drug should be flushed faster to push it through the vein
D) Actinomycin D is a potent vesicant, so the infusion must be stopped immediately and extravasation managed per protocol to prevent severe local tissue injury; clinicians should also remember its radiation-sensitizing property when radiotherapy is planned
E) Extravasation matters only with bleomycin, not with actinomycin D
ANSWER: D
Rationale:
Actinomycin D is a potent vesicant; extravasation can cause severe local tissue necrosis, so the infusion must be stopped immediately and managed according to extravasation protocol. Clinicians should also recall that actinomycin D is a radiation sensitizer (it impairs transcription of DNA repair enzymes), which is relevant when radiotherapy is part of the treatment plan.
Option A: Option A is incorrect because actinomycin D is a vesicant, not a non-irritant, so continuing the infusion would worsen tissue injury.
Option B: Option B is incorrect because vesicant extravasation is far from harmless and can cause significant necrosis.
Option C: Option C is incorrect because flushing faster would force more vesicant into the tissue, increasing injury.
Option E: Option E is incorrect because actinomycin D extravasation is a serious concern in its own right; the vesicant warning is not limited to other drugs.
9. A 49-year-old woman with HER2-positive breast cancer (overexpressing the human epidermal growth factor receptor 2) is to receive an anthracycline-containing regimen plus trastuzumab (an anti-HER2 monoclonal antibody). The oncologist plans the anthracycline first and trastuzumab afterward, with periodic left ventricular ejection fraction monitoring. What is the rationale for this sequencing and monitoring plan?
A) Trastuzumab chemically degrades doxorubicin if given in the same period
B) Trastuzumab and anthracyclines have additive cardiotoxicity, so giving them sequentially rather than concurrently reduces the combined risk of heart failure, and serial LVEF monitoring detects early cardiac dysfunction
C) Sequencing is done only to reduce infusion-reaction risk, not for cardiac safety
D) Trastuzumab accelerates anthracycline clearance, so concurrent dosing would be subtherapeutic
E) The two drugs share the topoisomerase II target and cancel each other if given together
ANSWER: B
Rationale:
Trastuzumab and anthracyclines both stress the myocardium and their cardiotoxic effects are additive, so administering them sequentially rather than concurrently lowers the combined heart-failure risk, and serial LVEF monitoring is used to detect early cardiac dysfunction so therapy can be adjusted.
Option A: Option A is incorrect because the concern is additive in-patient cardiotoxicity, not chemical degradation of doxorubicin by trastuzumab.
Option C: Option C is incorrect because the sequencing is specifically for cardiac safety, not merely to limit infusion reactions.
Option D: Option D is incorrect because trastuzumab does not accelerate anthracycline clearance; sequencing is not a pharmacokinetic dosing maneuver.
Option E: Option E is incorrect because trastuzumab targets HER2, not topoisomerase II, so the two do not compete for a shared target.
10. A 33-year-old man cured of a testicular germ cell tumor with an etoposide-containing regimen presents two years later with fatigue, pancytopenia, and circulating blasts. There was no antecedent period of cytopenias suggestive of myelodysplasia. Which diagnosis and confirmatory test should be prioritized?
A) Relapsed germ cell tumor; obtain serum tumor markers only
B) Aplastic anemia; obtain a bone marrow biopsy looking for an empty marrow
C) Vitamin B12 deficiency; check serum B12 and methylmalonic acid
D) Alkylating-agent-related leukemia; expect monosomy 7 and a long latency
E) Treatment-related acute myeloid leukemia from the topoisomerase II poison etoposide; prioritize bone marrow examination with cytogenetics specifically looking for an MLL rearrangement at chromosome 11q23
ANSWER: E
Rationale:
A short latency of about two years, an abrupt leukemic presentation without a preceding myelodysplastic phase, and prior etoposide exposure point to topoisomerase II poison-related acute myeloid leukemia; the confirmatory step is bone marrow examination with cytogenetics specifically seeking the characteristic MLL rearrangement at 11q23.
Option A: Option A is incorrect because pancytopenia with circulating blasts indicates a marrow process (leukemia), not relapsed germ cell tumor, which is assessed by markers and imaging.
Option B: Option B is incorrect because the presence of blasts indicates leukemia rather than aplastic anemia, which shows marrow hypoplasia without blasts.
Option C: Option C is incorrect because B12 deficiency does not produce circulating blasts and does not fit prior etoposide exposure with this presentation.
Option D: Option D is incorrect because monosomy 7 with long latency and a preceding myelodysplastic phase characterizes alkylating-agent leukemia, which is the contrasting pattern, not the short-latency 11q23/MLL etoposide signature seen here.
11. A 55-year-old woman received epirubicin during adjuvant breast cancer therapy several years ago. She now has a new malignancy for which doxorubicin is proposed. Before writing the order, the oncologist wants to estimate how much of the patient's safe lifetime anthracycline exposure remains. What is the correct approach?
A) Ignore the prior epirubicin because it was a different anthracycline given for a different cancer
B) Count only the new doxorubicin, since the prior course was years ago and has cleared
C) Convert the prior epirubicin dose and the planned doxorubicin dose into common doxorubicin-equivalent units and sum them, because anthracycline cardiotoxicity is cumulative and irreversible across all lifetime exposure regardless of which anthracycline was used
D) Add the raw milligrams of epirubicin and doxorubicin together without any conversion factor
E) Assume the cardiac risk resets with each new cancer diagnosis
ANSWER: C
Rationale:
Because anthracycline cardiotoxicity reflects cumulative, irreversible cardiomyocyte injury that accrues across all anthracycline exposure, the correct method is to express the prior epirubicin and the planned doxorubicin in common doxorubicin-equivalent units (epirubicin is less cardiotoxic per milligram, so a conversion factor applies) and sum them to estimate the remaining safe lifetime margin.
Option A: Option A is incorrect because prior anthracycline exposure of any type counts toward cumulative cardiac risk and cannot be ignored.
Option B: Option B is incorrect because plasma clearance of the earlier drug does not reverse the accumulated cardiac injury, so prior dosing still counts.
Option D: Option D is incorrect because raw milligram addition ignores the different per-milligram cardiotoxicity of epirubicin and doxorubicin; conversion to equivalents is required.
Option E: Option E is incorrect because cardiac risk does not reset with a new diagnosis; the cumulative principle persists across the patient's lifetime.
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