Anticancer Drugs — MCQs

Anticancer Drugs Indian Medical PG Practice Questions and MCQs

Question 151: Which of the following anticancer drugs is known to be cardiotoxic?

A. Methotrexate
B. Cyclophosphamide
C. Adriamycin (Correct Answer)
D. Vincristine

Explanation: **Explanation:** **Adriamycin (Doxorubicin)**, an anthracycline antibiotic, is the correct answer. Its primary dose-limiting toxicity is **cardiotoxicity**. This occurs via two mechanisms: the generation of iron-dependent free radicals (superoxide anions) that cause lipid peroxidation of the myocardial membrane, and the inhibition of Topoisomerase IIβ in cardiomyocytes. This can manifest as acute arrhythmias or, more commonly, chronic **dilated cardiomyopathy** leading to congestive heart failure. **Analysis of Incorrect Options:** * **Methotrexate:** An antimetabolite (folate antagonist) primarily known for bone marrow suppression, mucositis, and hepatotoxicity. High doses can cause nephrotoxicity. * **Cyclophosphamide:** An alkylating agent. While very high doses (used in bone marrow transplants) can cause acute carditis, its "signature" high-yield side effect is **hemorrhagic cystitis** (prevented by Mesna). * **Vincristine:** A vinca alkaloid that inhibits microtubule assembly. Its hallmark toxicity is **peripheral neuropathy** (paresthesia, loss of deep tendon reflexes) and autonomic dysfunction (constipation). It is notably bone marrow-sparing. **High-Yield Clinical Pearls for NEET-PG:** 1. **Dexrazoxane:** An iron chelator used to prevent/reduce Adriamycin-induced cardiotoxicity. 2. **Monitoring:** Patients on Adriamycin should have regular **ECHO/MUGA scans** to monitor the Left Ventricular Ejection Fraction (LVEF). 3. **Lifetime Dose:** The risk of heart failure increases significantly once the cumulative dose of Doxorubicin exceeds **450–550 mg/m²**. 4. **Trastuzumab:** Another high-yield cardiotoxic drug (HER2 inhibitor), but unlike Adriamycin, its cardiotoxicity is usually reversible and not dose-dependent.

Question 152: Which antineoplastic agent is known for its potential cardiotoxicity?

A. Doxorubicin (Correct Answer)
B. Bleomycin
C. Fluorouracil
D. Dacarbazine

Explanation: **Explanation:** **Doxorubicin** (an Anthracycline antibiotic) is the correct answer because its most notorious dose-limiting toxicity is **cardiotoxicity**. This occurs via the generation of iron-dependent **free radicals** (superoxide anions) and increased oxidative stress, leading to lipid peroxidation of the myocardial membranes. Since the heart has low levels of the protective enzyme *catalase*, it is particularly vulnerable to this damage. **Analysis of Options:** * **Bleomycin:** Known primarily for **Pulmonary Fibrosis** ("Bleo-Lung"). It lacks significant cardiac side effects. * **Fluorouracil (5-FU):** Primarily causes gastrointestinal distress, mucositis, and myelosuppression. While it can rarely cause coronary vasospasm, it is not the classic answer for general cardiotoxicity. * **Dacarbazine:** An alkylating agent used in melanoma and Hodgkin lymphoma; its main side effects are severe nausea, vomiting, and myelosuppression. **High-Yield Clinical Pearls for NEET-PG:** 1. **Two types of Doxorubicin Cardiotoxicity:** * *Acute:* Transient ECG changes (arrhythmias, ST-T changes). * *Chronic:* Cumulative dose-dependent **Dilated Cardiomyopathy** leading to Congestive Heart Failure (CHF). 2. **Dose Limit:** Risk increases significantly when the cumulative dose exceeds **550 mg/m²**. 3. **Prevention:** **Dexrazoxane**, an iron-chelating agent, is administered to reduce the formation of free radicals and protect the myocardium. 4. **Monitoring:** Periodic **Echocardiography** or MUGA scans to monitor Left Ventricular Ejection Fraction (LVEF) is mandatory.

Question 153: Which of the following is NOT true regarding selective estrogen receptor down-regulator (SERD), Fulvestrant?

A. Used for treatment of advanced breast cancer.
B. Is a selective estrogen antagonist.
C. Is slower and short acting and less safer than SERMs. (Correct Answer)
D. Administered as once a month i.m. dose.

Explanation: **Explanation:** **Fulvestrant** is a unique anticancer agent classified as a **Selective Estrogen Receptor Down-regulator (SERD)** [1]. Unlike SERMs (like Tamoxifen), which have agonist effects in some tissues and antagonist effects in others, Fulvestrant is a **pure estrogen antagonist** [1]. **Why Option C is the correct (False) statement:** Fulvestrant is actually **long-acting** and has a **better safety profile** regarding uterine health compared to SERMs. It is formulated in an oil-based vehicle for slow release, giving it a long half-life (approx. 40 days) [1]. Furthermore, because it lacks the partial agonist activity of Tamoxifen, it does **not** increase the risk of endometrial cancer or venous thromboembolism, making it "safer" in those specific contexts. **Analysis of Incorrect Options:** * **Option A:** It is FDA-approved for the treatment of **hormone receptor-positive (HR+) metastatic or advanced breast cancer**, especially in postmenopausal women who have progressed on anti-estrogen therapy. * **Option B:** It binds to the estrogen receptor (ER) and triggers its degradation (down-regulation) [1]. It has **zero agonist activity**, making it a pure/selective antagonist [1]. * **Option C:** Due to its long half-life, it is conveniently administered as a **500 mg intramuscular (i.m.) injection once a month** (with an additional loading dose two weeks after the first) [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Competitive inhibition of ER binding + acceleration of ER degradation (proteasomal pathway) [1]. * **SERM vs. SERD:** Tamoxifen (SERM) increases endometrial cancer risk; Fulvestrant (SERD) does not. * **Side Effects:** Most common are injection site pain, hot flashes, and nausea. * **Indication:** Often used in combination with CDK4/6 inhibitors (e.g., Palbociclib) for advanced breast cancer.

Question 154: What is the most characteristic side effect of adriamycin?

A. Nephrotoxicity
B. Neurotoxicity
C. Cardiotoxicity (Correct Answer)
D. Hemorrhagic cystitis

Explanation: **Explanation:** **Adriamycin (Doxorubicin)** is an anthracycline antibiotic used widely in cancer chemotherapy. The most characteristic and dose-limiting side effect of this drug is **Cardiotoxicity**. **Why Cardiotoxicity occurs:** Doxorubicin generates **free radicals** (superoxide anions) through an iron-dependent process. The myocardium is particularly vulnerable because it has low levels of protective enzymes like **catalase** and **glutathione peroxidase**. This leads to oxidative stress, resulting in: 1. **Acute toxicity:** Arrhythmias and ECG changes (usually reversible). 2. **Chronic toxicity:** Dilated cardiomyopathy and congestive heart failure (dose-dependent and often irreversible). **Analysis of Incorrect Options:** * **A. Nephrotoxicity:** Characteristic of **Cisplatin**. While many drugs are cleared renally, Adriamycin is primarily metabolized by the liver. * **B. Neurotoxicity:** Classic side effect of **Vincristine** (peripheral neuropathy) or **Paclitaxel**. * **D. Hemorrhagic cystitis:** This is the hallmark toxicity of **Cyclophosphamide** and **Ifosfamide**, caused by the metabolite **Acrolein**. **High-Yield Clinical Pearls for NEET-PG:** * **Antidote:** **Dexrazoxane** (an iron chelator) is used to prevent/reduce doxorubicin-induced cardiotoxicity. * **Dose Limit:** The risk of heart failure increases significantly once the cumulative dose exceeds **550 mg/m²**. * **Monitoring:** Periodic **ECHO or MUGA scans** are mandatory to monitor the Left Ventricular Ejection Fraction (LVEF). * **Appearance:** It is often called the "Red Devil" because it can cause harmless red discoloration of urine.

Question 155: Which of the following drugs is used in the treatment of estrogen-dependent breast carcinoma?

A. Tamoxifen (Correct Answer)
B. Methotrexate
C. Paclitaxel
D. Adriamycin

Explanation: ### Explanation **Correct Option: A (Tamoxifen)** Tamoxifen is the gold standard for treating **estrogen receptor-positive (ER+) breast cancer** [1]. It belongs to the class of **Selective Estrogen Receptor Modulators (SERMs)**. Its mechanism of action is tissue-specific: it acts as a **competitive antagonist** at estrogen receptors in breast tissue, thereby inhibiting the growth of estrogen-dependent tumor cells [1]. However, it acts as a partial agonist in the bone (preventing osteoporosis) and the endometrium. **Analysis of Incorrect Options:** * **B. Methotrexate:** An antimetabolite that inhibits **dihydrofolate reductase (DHFR)**. While used in some breast cancer regimens (e.g., CMF protocol), it is a non-hormonal cytotoxic agent and does not specifically target estrogen-dependent pathways. * **C. Paclitaxel:** A taxane that stabilizes **microtubules**, preventing mitosis. It is used for advanced or node-positive breast cancer regardless of ER status but is not a hormone-specific therapy. * **D. Adriamycin (Doxorubicin):** An anthracycline antibiotic that inhibits **Topoisomerase II** and generates free radicals. It is a potent cytotoxic drug used in many breast cancer protocols (e.g., AC regimen) but lacks specificity for estrogen-dependent mechanisms. **High-Yield Clinical Pearls for NEET-PG:** * **Adverse Effect:** Tamoxifen increases the risk of **endometrial carcinoma** (due to its agonist effect on the uterus) and **thromboembolism** [1]. * **Drug of Choice:** Tamoxifen is used in both pre- and post-menopausal women, whereas **Aromatase Inhibitors** (e.g., Letrozole, Anastrozole) are preferred specifically for post-menopausal ER+ breast cancer [1]. * **Prophylaxis:** Tamoxifen is also approved for the primary prevention of breast cancer in high-risk women.

Question 156: Bleomycin causes damage to which of the following cellular components in the lung?

A. Type 1 pneumocytes (Correct Answer)
B. Type 2 pneumocytes
C. Both Type 1 and Type 2 pneumocytes
D. Pulmonary endothelial cells

Explanation: **Explanation:** **Mechanism of Action & Target:** Bleomycin is a cytotoxic antibiotic that acts by binding to DNA and creating free radicals (superoxide and hydroxyl radicals), leading to single- and double-strand breaks. Its most notorious dose-limiting toxicity is **pulmonary fibrosis**. The primary target of this oxidative damage in the lungs is the **Type 1 pneumocyte**. These cells are particularly vulnerable because they lack the enzyme **Bleomycin hydrolase**, which normally inactivates the drug in other tissues (like the liver). Damage to Type 1 pneumocytes leads to alveolar wall thickening, inflammatory cell infiltration, and subsequent irreversible fibrosis. **Analysis of Options:** * **Option A (Correct):** Type 1 pneumocytes are the structural cells covering 95% of the alveolar surface. Their destruction by free radicals is the initiating event in Bleomycin-induced lung injury. * **Option B & C (Incorrect):** While Type 2 pneumocytes may proliferate as a compensatory mechanism to repair the damaged alveolar epithelium, they are not the primary site of initial damage. * **Option D (Incorrect):** Although some endothelial damage occurs, the hallmark of Bleomycin toxicity is the destruction of the alveolar epithelial lining (Type 1 cells). **High-Yield NEET-PG Pearls:** 1. **Enzyme Deficiency:** The lung and skin have low levels of **Bleomycin hydrolase**, explaining why toxicity is localized to these organs (Pulmonary fibrosis and Skin hyperpigmentation/flagellate dermatitis). 2. **Monitoring:** Patients on Bleomycin should be monitored with **DLCO (Diffusion Capacity of Carbon Monoxide)**; a decrease in DLCO often precedes symptomatic respiratory distress. 3. **Risk Factor:** High inspired oxygen concentrations (e.g., during surgery) can exacerbate Bleomycin lung injury due to increased free radical formation. 4. **Cell Cycle:** Bleomycin is **G2 phase-specific**.

Question 157: Ipilimumab is a:

A. Anti CD30 Monoclonal Antibody
B. PDL1 receptor inhibitor
C. CTLA4 inhibitor (Correct Answer)
D. PTPN22 inhibitor

Explanation: **Ipilimumab** is a recombinant human monoclonal antibody that acts as an **immune checkpoint inhibitor**. Its primary mechanism involves binding to and blocking **CTLA-4** (Cytotoxic T-Lymphocyte Antigen 4), a molecule expressed on the surface of T-cells. Normally, CTLA-4 acts as an "off switch" to prevent overactivation of the immune system. By inhibiting this checkpoint, Ipilimumab allows T-cells to remain active and mount an effective immune response against tumor cells. It is primarily used in the treatment of advanced (metastatic) melanoma [1].**Analysis of Incorrect Options:** * **Option A (Anti-CD30):** This describes **Brentuximab vedotin**, which is used in Hodgkin lymphoma and Anaplastic large cell lymphoma [1]. * **Option B (PD-L1 inhibitor):** Drugs in this class include **Atezolizumab, Durvalumab, and Avelumab**. (Note: Nivolumab and Pembrolizumab are PD-1 inhibitors, not PD-L1). * **Option D (PTPN22 inhibitor):** PTPN22 is a gene associated with autoimmune diseases (like Rheumatoid Arthritis); there are currently no standard anticancer monoclonal antibodies targeting this in clinical practice.**High-Yield Clinical Pearls for NEET-PG:**1. **Mechanism:** Ipilimumab works at the **priming phase** (lymph node level), whereas PD-1 inhibitors work at the **effector phase** (tumor microenvironment).2. **Adverse Effects:** Checkpoint inhibitors cause **immune-related Adverse Events (irAEs)**, such as colitis, dermatitis, and hypophysitis (pituitary inflammation), and anti-CTLA-4 antibodies can be associated with autoimmune toxicity [1].3. **FDA Approval:** It was the first checkpoint inhibitor to show a survival benefit in metastatic melanoma.

Question 158: Inhibition of which of the following enzymes is responsible for the anticancer action of 5-Fluorouracil?

A. Dihydrofolate reductase
B. Thymidylate kinase
C. Thymidylate reductase
D. Thymidylate synthase (Correct Answer)

Explanation: ### Explanation **1. Why Thymidylate Synthase is the Correct Answer:** 5-Fluorouracil (5-FU) is a pyrimidine antimetabolite. Inside the cell, it is converted into its active metabolite, **5-fluoro-2'-deoxyuridine-5'-monophosphate (FdUMP)**. FdUMP acts as a suicide inhibitor by forming a stable ternary complex with the enzyme **Thymidylate Synthase** and the cofactor N5,N10-methylene tetrahydrofolate. This inhibition prevents the conversion of deoxyuridylate (dUMP) to deoxythymidylate (dTMP). The resulting "thymine-less death" halts DNA synthesis and repair, leading to the drug's cytotoxic effect. **2. Analysis of Incorrect Options:** * **A. Dihydrofolate reductase (DHFR):** This enzyme is inhibited by **Methotrexate**. While 5-FU and Methotrexate both affect the folate pathway, their primary targets are distinct. * **B. Thymidylate kinase:** This enzyme converts dTMP to dTDP. It is not the primary target of 5-FU. * **C. Thymidylate reductase:** This is a distractor; the relevant enzyme in this pathway is a synthase, not a reductase. **3. High-Yield Clinical Pearls for NEET-PG:** * **Synergy:** Leucovorin (folinic acid) is often given with 5-FU because it increases the stability of the FdUMP-Thymidylate Synthase complex, thereby **potentiating** the efficacy of 5-FU (unlike its role as a "rescue" agent for Methotrexate). * **Pharmacogenetics:** Patients with **Dihydropyrimidine Dehydrogenase (DPD) deficiency** are at high risk of severe, life-threatening toxicity when treated with 5-FU. * **Adverse Effects:** Hand-foot syndrome (palmar-plantar erythrodysesthesia) and GI toxicity/mucositis are characteristic side effects. * **Topical Use:** 5-FU is used topically for actinic keratosis and superficial basal cell carcinoma.

Question 159: Folinic acid counteracts the toxicity of which of the following agents?

A. Doxorubicin
B. Methotrexate (Correct Answer)
C. Cyclophosphamide
D. Fluorouracil

Explanation: **Explanation:** **Methotrexate (MTX)** is a folate antagonist that inhibits the enzyme **Dihydrofolate Reductase (DHFR)** [1]. This inhibition prevents the conversion of dihydrofolate to tetrahydrofolate (THF), the active form of folic acid required for DNA synthesis [1]. **Folinic acid (Leucovorin)** is a reduced form of folate that does not require DHFR for activation [1]. By providing a source of active folate downstream of the metabolic block, it "rescues" normal cells from MTX-induced bone marrow and GI toxicity [2]. This strategy is known as **Leucovorin Rescue** [2]. **Analysis of Incorrect Options:** * **A. Doxorubicin:** Toxicity (Cardiotoxicity) is managed with **Dexrazoxane**, an iron chelator that reduces free radical formation. * **C. Cyclophosphamide:** Hemorrhagic cystitis caused by its metabolite *acrolein* is managed with **MESNA** and aggressive hydration. * **D. Fluorouracil (5-FU):** While Folinic acid is used with 5-FU, it is **not** used to counteract toxicity. Instead, it acts as a **potentiator** [2]. It stabilizes the binding of 5-dUMP to thymidylate synthase, enhancing the drug's efficacy [2]. **High-Yield Clinical Pearls for NEET-PG:** * **Leucovorin Rescue** is typically initiated 24 hours after high-dose MTX to allow the drug to kill tumor cells first. * **Glucarpidase** is another agent used in MTX toxicity; it directly breaks down MTX in the blood. * **Vincristine** toxicity (peripheral neuropathy) has no specific rescue agent; treatment is symptomatic. * **Amifostine** is used to reduce nephrotoxicity associated with **Cisplatin**.

Question 160: Which chemotherapeutic agent is most commonly administered by continuous infusion?

A. Cytarabine (Ara-C) (Correct Answer)
B. 5-Fluorouracil (5-FU)
C. Cisplatin
D. Etoposide

Explanation: **Explanation:** **Why Cytarabine (Ara-C) is the Correct Answer:** Cytarabine is a **cell-cycle specific (S-phase)** antimetabolite. Its mechanism involves inhibition of DNA polymerase. The primary reason for continuous infusion is its **extremely short half-life** (approximately 10–20 minutes) due to rapid deamination by the enzyme cytidine deaminase in the blood and liver. To maintain therapeutic plasma concentrations and ensure that leukemic cells entering the S-phase at different times are exposed to the drug, it is traditionally administered via continuous intravenous infusion (e.g., in the "7+3" regimen for AML). **Analysis of Incorrect Options:** * **5-Fluorouracil (5-FU):** While 5-FU is frequently given as a continuous infusion in colorectal cancer to improve the safety profile and efficacy, it is also commonly given as a bolus. In the context of standard pharmacological teaching for competitive exams, Cytarabine’s pharmacokinetics make it the classic prototype for continuous infusion. * **Cisplatin:** This is a cell-cycle non-specific alkylating-like agent. It is typically administered as a short-term infusion with aggressive pre- and post-hydration to prevent nephrotoxicity, rather than a continuous maintenance infusion. * **Etoposide:** An inhibitor of Topoisomerase II, usually administered as an intermittent intravenous infusion over 30–60 minutes to avoid hypotension. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Cytarabine is the backbone of Induction therapy for **Acute Myeloid Leukemia (AML)**. * **Specific Toxicity:** High-dose Cytarabine (HiDAC) is associated with **Cerebellar toxicity** (ataxia, nystagmus) and conjunctivitis (prophylactic steroid drops are used). * **Mechanism:** It is a pyrimidine analog (specifically a Cytidine analog).

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Principles of Cancer Chemotherapy

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Alkylating Agents

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Antimetabolites

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Antitumor Antibiotics

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Plant Alkaloids

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Topoisomerase Inhibitors

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Hormonal Agents

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Targeted Therapy

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Immunotherapy

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Management of Chemotherapy Side Effects

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