Anticancer Drugs — MCQs

Anticancer Drugs Indian Medical PG Practice Questions and MCQs

Question 151: 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 152: 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 153: 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 154: 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 155: 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 156: 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 157: 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 158: 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 159: 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).

Question 160: Paclitaxel acts on which phase of the cell cycle?

A. G1
B. S
C. G2
D. M (Correct Answer)

Explanation: **Explanation:** **Mechanism of Action (Why M phase is correct):** Paclitaxel belongs to the **Taxane** class of anticancer drugs. Its primary mechanism is the **stabilization of microtubules** [2]. Unlike Vinca alkaloids (which prevent microtubule assembly), Paclitaxel binds to the $\beta$-tubulin subunit and promotes the assembly of microtubules while inhibiting their disassembly (depolymerization) [2]. This results in the formation of non-functional, stable microtubule bundles, leading to "mitotic freeze." Consequently, the cell cannot form a functional mitotic spindle, arresting the cell cycle specifically in the **M (Mitosis) phase** [3, 5]. **Analysis of Incorrect Options:** * **G1 Phase:** Drugs like Corticosteroids or L-asparaginase typically act here. Paclitaxel requires the presence of mitotic spindles, which are absent in G1. * **S Phase:** This is the site of action for Antimetabolites (e.g., Methotrexate, 5-FU) and DNA polymerase inhibitors (e.g., Cytarabine), which interfere with DNA synthesis [3]. * **G2 Phase:** Drugs like Bleomycin and Etoposide primarily exert their effects in the late S or G2 phase [3]. **NEET-PG Clinical Pearls:** * **Source:** Paclitaxel is derived from the bark of the Pacific Yew tree (*Taxus brevifolia*) [2]. * **Adverse Effects:** The dose-limiting toxicity is **Bone Marrow Suppression** (Neutropenia). It is also notorious for causing **peripheral neuropathy** [1] and **hypersensitivity reactions** (often due to the Cremophor EL vehicle; premedication with dexamethasone and antihistamines is required) [1]. * **Albumin-bound Paclitaxel (Abraxane):** A newer formulation that reduces hypersensitivity risks [1]. * **Mnemonic:** **T**axanes **T**erminate (stabilize) the **T**ubules.

Practice by Chapter

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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