Anticancer Drugs — MCQs

Anticancer Drugs Indian Medical PG Practice Questions and MCQs

Question 411: All of the following are direct DNA interacting cytotoxic agents except?

A. Melphalan
B. Hydroxyurea (Correct Answer)
C. Carmustine
D. Ifosfamide

Explanation: ### Explanation The core concept in this question is the classification of anticancer drugs based on their mechanism of action: **Direct DNA-damaging agents** vs. **Antimetabolites**. **Why Hydroxyurea is the Correct Answer:** Hydroxyurea is an **antimetabolite** that acts as a **Ribonucleotide Reductase inhibitor**. It prevents the conversion of ribonucleotides to deoxyribonucleotides, thereby depleting the building blocks of DNA synthesis. It does not physically bind to or damage the DNA strand itself; rather, it inhibits the *synthesis* of new DNA. It is specifically **S-phase active**. **Why the Other Options are Incorrect:** * **Melphalan (Option A):** This is a nitrogen mustard and a classic **Alkylating agent**. It forms covalent bonds with DNA (specifically at the N7 position of guanine), causing cross-linking and direct structural damage. * **Carmustine (Option C):** This is a **Nitrosourea**. Like other alkylating agents, it causes direct DNA cross-linking and carbamoylation of proteins. * **Ifosfamide (Option D):** This is a nitrogen mustard (an analogue of cyclophosphamide). It is a pro-drug that is metabolized to active alkylating species which directly attack DNA. --- ### High-Yield Clinical Pearls for NEET-PG: * **Hydroxyurea Clinical Uses:** It is used in Chronic Myeloid Leukemia (CML), Polycythemia Vera, and notably in **Sickle Cell Anemia** (because it increases the production of **Fetal Hemoglobin/HbF**). * **Nitrosoureas (Carmustine/Lomustine):** These are highly lipid-soluble and cross the blood-brain barrier, making them the drugs of choice for **Brain Tumors (Gliomas)**. * **Ifosfamide Toxicity:** It can cause **Hemorrhagic Cystitis** due to the metabolite **Acrolein**. This is managed with aggressive hydration and **MESNA** (a sulfhydryl compound that neutralizes acrolein). * **Cell Cycle Specificity:** Alkylating agents (Melphalan, Ifosfamide) are **Cell Cycle Non-Specific (CCNS)**, whereas Hydroxyurea is **Cell Cycle Specific (CCS)** for the S-phase.

Question 412: Which of the following parameters is not monitored in a patient on methotrexate therapy?

A. Liver function tests
B. Lung function tests
C. Eye examination (Correct Answer)
D. Hemogram

Explanation: **Explanation:** Methotrexate (MTX) is a folate antimetabolite that inhibits the enzyme **dihydrofolate reductase (DHFR)**. While it is a cornerstone in treating malignancies and autoimmune conditions (like Rheumatoid Arthritis), it carries a significant profile of systemic toxicities. **Why Eye Examination is the Correct Answer:** Unlike drugs such as Hydroxychloroquine (which requires retinal monitoring) or Ethambutol (which causes optic neuritis), **Methotrexate does not typically cause ocular toxicity**. Therefore, routine eye examinations are not a standard part of MTX monitoring protocols. **Why other options are monitored:** * **Liver Function Tests (LFTs):** MTX is hepatotoxic. Chronic use can lead to elevated transaminases, steatosis, and eventually **hepatic fibrosis or cirrhosis**. Baseline and periodic LFTs are mandatory. * **Hemogram (CBC):** As a cytotoxic drug, MTX causes **bone marrow suppression** (myelosuppression), leading to leucopenia, thrombocytopenia, and anemia. Monitoring the CBC is critical to prevent life-threatening pancytopenia. * **Lung Function Tests:** MTX can induce **interstitial pneumonitis** (Methotrexate-induced lung injury) or pulmonary fibrosis. Patients presenting with a dry cough or dyspnea require urgent pulmonary evaluation. **High-Yield Clinical Pearls for NEET-PG:** * **Rescue Therapy:** **Leucovorin (Folinic acid)** is used to "rescue" normal cells from MTX toxicity by bypassing the inhibited DHFR enzyme. * **Nephrotoxicity:** High-dose MTX can precipitate in renal tubules; **vigorous hydration and urinary alkalinization** are required. * **Contraindication:** MTX is highly **teratogenic** (Category X) and must be avoided in pregnancy. * **Antidote for Overdose:** **Glucarpidase** (carboxypeptidase G2) can rapidly reduce toxic plasma MTX levels.

Question 413: Which of the following causes peripheral neuritis?

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

Explanation: **Explanation:** **Vincristine** is a Vinca alkaloid that acts as a **microtubule inhibitor**. It binds to tubulin and inhibits its polymerization into microtubules, leading to mitotic arrest in the M-phase. Microtubules are not only essential for cell division but are also critical for **axonal transport** in neurons. By disrupting these microtubule tracks, Vincristine interferes with the transport of neurotransmitters and essential proteins along the long axons of peripheral nerves, leading to **dose-limiting peripheral neuropathy (neuritis)**. This typically manifests as symmetrical "glove and stocking" paresthesia, loss of deep tendon reflexes, and motor weakness. **Why other options are incorrect:** * **Methotrexate:** A folate antagonist (antimetabolite) primarily known for bone marrow suppression, mucositis, and hepatotoxicity. It can cause neurotoxicity (leukoencephalopathy) if given intrathecally, but peripheral neuritis is not its hallmark. * **Busulfan:** An alkylating agent (alkyl sulfonate) most famous for causing **pulmonary fibrosis** ("Busulfan lung") and hyperpigmentation (Addisonian-like syndrome). * **Cyclophosphamide:** An alkylating agent (nitrogen mustard) notorious for **hemorrhagic cystitis** due to the metabolite **Acrolein**. It is also highly emetogenic and causes alopecia. **High-Yield Clinical Pearls for NEET-PG:** * **Vincristine vs. Vinblastine:** Remember the mnemonic: **Vincristine** = **C**NS/Nerve toxicity (Peripheral neuropathy); **Vinblastine** = **B**last (Bone marrow suppression). * Vincristine is notably **bone marrow sparing**, making it ideal for combination regimens. * **Fatal Error:** Vincristine is for **Intravenous use ONLY**. Intrathecal administration is fatal due to ascending myeloencephalopathy. * Other anticancer drugs causing peripheral neuropathy: **Paclitaxel** (microtubule stabilizer) and **Cisplatin** (platinum compound).

Question 414: Which of the following is/are used in the hormonal therapy of breast carcinoma?

A. Letrozole
B. Anastrozole
C. Tamoxifen
D. All of the above (Correct Answer)

Explanation: Hormonal therapy is a cornerstone in the management of hormone receptor-positive (ER/PR+) breast cancer. The goal is to either block estrogen receptors or decrease circulating estrogen levels. **Explanation of Options:** * **Tamoxifen (Option C):** This is a **Selective Estrogen Receptor Modulator (SERM)**. It acts as a competitive antagonist at estrogen receptors in breast tissue, making it the gold standard for pre-menopausal women. It also has agonist effects on the bone (preventing osteoporosis) and endometrium (increasing the risk of endometrial carcinoma). * **Letrozole and Anastrozole (Options A & B):** These are **Third-generation Aromatase Inhibitors (AIs)**. They inhibit the enzyme aromatase, which converts peripheral androgens into estrogens. Since they cannot stop ovarian estrogen production, they are primarily used in **post-menopausal women**. **Why "All of the above" is correct:** All three drugs are FDA-approved and standard-of-care agents used to treat or prevent the recurrence of breast carcinoma by targeting the estrogen signaling pathway. **High-Yield Clinical Pearls for NEET-PG:** 1. **Drug of Choice:** Tamoxifen is preferred in pre-menopausal women; Aromatase Inhibitors (Letrozole/Anastrozole) are preferred in post-menopausal women. 2. **Side Effects:** Tamoxifen increases the risk of **thromboembolism** and **endometrial cancer**. Aromatase inhibitors are associated with an increased risk of **osteoporosis** and joint pain. 3. **Fulvestrant:** A Selective Estrogen Receptor Downregulator (SERD) used in tamoxifen-resistant cases. 4. **Trastuzumab:** Not a hormonal agent, but a monoclonal antibody used for HER2/neu positive breast cancer.

Question 415: Which of the following is the main mechanism by which mechlorethamine exerts its cell killing?

A. Alkylating DNA, causing cross-links between parallel DNA strands (Correct Answer)
B. Blocking microtubular assembly and mitosis during M-phase
C. Inhibiting topoisomerase, preventing repair of DNA strand breaks
D. Intercalating in DNA strands, thereby preventing DNA replication by mRNA

Explanation: **Explanation:** **Mechlorethamine** is the prototype of the **Nitrogen Mustards**, which belong to the class of **Alkylating Agents**. These drugs are cell-cycle non-specific (CCNS) but are most effective during the late G1 and S phases. 1. **Mechanism of Action (Option A):** Mechlorethamine undergoes an intramolecular cyclization to form a highly reactive **ethyleniminium ion**. This intermediate acts as an electrophile that attaches an alkyl group to the **N7 position of Guanine** in DNA. Because mechlorethamine is bifunctional (has two reactive groups), it can bind to two different guanine bases, primarily causing **inter-strand cross-linking**. This prevents the separation of DNA strands, inhibiting replication and transcription, ultimately leading to apoptosis. 2. **Analysis of Incorrect Options:** * **Option B:** This describes **Vinca Alkaloids** (e.g., Vincristine, Vinblastine), which bind to tubulin and inhibit microtubule polymerization. * **Option C:** This describes **Topoisomerase inhibitors** such as Etoposide (Topoisomerase II) or Irinotecan (Topoisomerase I). * **Option D:** This describes **Antitumor Antibiotics** (e.g., Doxorubicin, Dactinomycin), which intercalate between base pairs. Note: mRNA is involved in translation, not DNA replication. **High-Yield NEET-PG Pearls:** * **MOPP Regimen:** Mechlorethamine was historically a key component of the MOPP regimen for **Hodgkin’s Lymphoma** (Mechlorethamine, Oncovin, Procarbazine, Prednisone). * **Vesicant Property:** It is a potent vesicant; accidental extravasation causes severe tissue necrosis. Sodium thiosulfate is used as an antidote. * **Dose-limiting toxicity:** Bone marrow suppression (myelosuppression).

Question 416: Imatinib is used in the treatment of which of the following conditions?

A. Chronic myelomonocytic leukemia
B. Myelodysplastic syndrome
C. Acute lymphoblastic leukemia
D. Gastrointestinal stromal tumors (Correct Answer)

Explanation: **Explanation:** **Imatinib** is a revolutionary targeted therapy that acts as a selective **tyrosine kinase inhibitor (TKI)** [4]. Its primary mechanism involves inhibiting the Bcr-Abl tyrosine kinase, but it also potently inhibits the **c-KIT (CD117)** and **PDGFR** (Platelet-Derived Growth Factor Receptor) tyrosine kinases [1], [5]. 1. **Why Option D is correct:** Gastrointestinal Stromal Tumors (GIST) are characterized by the overexpression of the **c-KIT receptor tyrosine kinase** (in ~95% of cases). Imatinib binds to the ATP-binding site of the c-KIT receptor, blocking downstream signaling and tumor proliferation [2], [5]. It is the first-line medical treatment for metastatic or unresectable GIST. 2. **Why other options are incorrect:** * **Chronic Myelomonocytic Leukemia (CMML):** While Imatinib is the gold standard for Chronic *Myeloid* Leukemia (CML), it is not the standard for CMML, which often requires hypomethylating agents like Azacitidine. * **Myelodysplastic Syndrome (MDS):** MDS is typically treated with Lenalidomide or supportive care; Imatinib has no role unless a specific PDGFR rearrangement is present (rare). * **Acute Lymphoblastic Leukemia (ALL):** Imatinib is only used in the specific subtype of **Philadelphia chromosome-positive (Ph+) ALL** [3]. It is not a general treatment for all ALL cases. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice (DOC):** Chronic Myeloid Leukemia (CML) – targets the Philadelphia chromosome $t(9;22)$ [4]. * **Mechanism:** Competitive inhibition of the ATP-binding site [2]. * **Side Effects:** Fluid retention (periorbital edema), muscle cramps, and hepatotoxicity. * **Resistance:** Often occurs due to point mutations in the kinase domain (e.g., **T315I mutation**), which requires second-generation TKIs like **Dasatinib** or **Nilotinib** [3].

Question 417: All of the following statements about methotrexate are true EXCEPT:

A. It is cell cycle specific and kills cells in the S phase.
B. Its toxicity primarily affects bone marrow and epithelial structures.
C. Folic acid reverses its toxic effects. (Correct Answer)
D. It is the drug of choice for choriocarcinoma.

Explanation: ### Explanation **1. Why Option C is the correct (False) statement:** Methotrexate (MTX) is a folate antagonist that works by inhibiting the enzyme **Dihydrofolate Reductase (DHFR)**. This prevents the conversion of dihydrofolate to tetrahydrofolate (THF). Once MTX binds to DHFR, the cell’s pool of active folate is depleted. Administering **Folic acid** is ineffective because it also requires DHFR to be converted into its active form. To reverse MTX toxicity, we must provide **Folinic acid (Leucovorin/Citrovorum factor)**, which is already a reduced form of folate (N5-formyl-THF) that bypasses the inhibited enzyme. This is known as **"Leucovorin Rescue."** **2. Analysis of other options:** * **Option A:** MTX is a classic **Antimetabolite**. These drugs are **Cell Cycle Specific (CCS)** and act specifically during the **S-phase** by inhibiting DNA synthesis. * **Option B:** Like most cytotoxic drugs, MTX targets rapidly dividing cells. Its primary dose-limiting toxicities include **Bone Marrow Suppression** (myelosuppression) and damage to **Epithelial structures** (leading to oral mucositis and GI ulceration). * **Option D:** MTX is highly effective against trophoblastic tumors and remains the **Drug of Choice for Choriocarcinoma**, often achieving a 100% cure rate in low-risk cases. **3. NEET-PG High-Yield Clinical Pearls:** * **Resistance:** Occurs via decreased drug uptake, decreased polyglutamation, or altered DHFR with lower affinity for MTX. * **Excretion:** MTX is primarily excreted renally. **Salicylates and Sulfonamides** can displace MTX from plasma proteins and inhibit its renal secretion, leading to fatal toxicity. * **Other Uses:** Low-dose MTX is a first-line **Disease-Modifying Antirheumatic Drug (DMARD)** for Rheumatoid Arthritis and is used in Ectopic Pregnancy. * **Specific Toxicity:** Long-term use can lead to **Hepatic Fibrosis/Cirrhosis**.

Question 418: Leucovorin is used to decrease the toxicity of which of the following drugs?

A. Methotrexate (Correct Answer)
B. 6-Mercaptopurine
C. Thio-TEPA
D. Cytosine arabinoside

Explanation: **Explanation:** **1. Why Methotrexate is Correct:** 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. [3] **Leucovorin (Folinic Acid)** is a reduced form of folate that does not require DHFR for activation. [1] When administered after high-dose MTX, it bypasses the blocked enzyme to provide a source of THF for healthy cells, effectively "rescuing" them from bone marrow and GI toxicity. [3] This process is known as **Leucovorin Rescue.** [4] **2. Why Other Options are Incorrect:** * **6-Mercaptopurine (6-MP):** This is a purine antimetabolite. Its toxicity is managed by dose reduction, especially when co-administered with Allopurinol (which inhibits its metabolism by Xanthine Oxidase). [2] * **Thio-TEPA:** This is an alkylating agent. Its primary toxicity is myelosuppression, which is managed with supportive care or growth factors (G-CSF), not Leucovorin. * **Cytosine Arabinoside (Cytarabine):** This is a pyrimidine antagonist. Its dose-limiting toxicity is bone marrow suppression and cerebellar ataxia; Leucovorin has no role in its metabolic pathway. **3. High-Yield Clinical Pearls for NEET-PG:** * **Potentiation:** While Leucovorin *decreases* MTX toxicity, it is used to *increase* the efficacy of **5-Fluorouracil (5-FU)** by stabilizing the binding of 5-dUMP to thymidylate synthase. * **Glucarpidase:** An alternative for MTX toxicity in patients with renal failure; it enzymatically cleaves MTX into inactive metabolites. * **Timing:** Leucovorin rescue must be started within 24–42 hours of MTX administration to be effective.

Question 419: Which of the following drugs cause metaphase arrest?

A. Vincristine, Paclitaxel, Colchicine (Correct Answer)
B. Griseofulvin, Vincristine, Paclitaxel
C. Griseofulvin, Paclitaxel, Etoposide
D. Vincristine, Etoposide, Colchicine

Explanation: ### Explanation **1. Mechanism of Metaphase Arrest** Metaphase arrest occurs when drugs interfere with the **mitotic spindle apparatus**, preventing the separation of sister chromatids. This triggers the "spindle assembly checkpoint," halting the cell cycle in the **M-phase (Metaphase)**. * **Vinca Alkaloids (Vincristine/Vinblastine):** These bind to tubulin and **inhibit polymerization**, preventing the formation of microtubules ("Spindle poisons"). * **Taxanes (Paclitaxel/Docetaxel):** These bind to tubulin and **enhance polymerization**, stabilizing microtubules and preventing their disassembly ("Spindle stabilizers"). * **Colchicine:** Primarily used in gout, it also inhibits microtubule polymerization, leading to metaphase arrest. **2. Analysis of Incorrect Options** * **Option B & C (Griseofulvin):** While Griseofulvin is an antifungal that interferes with microtubule function, it is **not** classified as a standard anticancer drug. Furthermore, Option C includes Etoposide. * **Option C & D (Etoposide):** Etoposide is a **Topoisomerase II inhibitor**. It acts primarily in the **S and G2 phases** of the cell cycle, not the M-phase. It causes DNA strand breaks rather than spindle interference. **3. NEET-PG High-Yield Pearls** * **Cell Cycle Specificity:** Vincas and Taxanes are **M-phase specific**. * **Dose-Limiting Toxicities:** * **Vincristine:** Peripheral neuropathy (Areflexia, paralytic ileus). Note: It is relatively bone marrow sparing. * **Vinblastine:** Bone marrow suppression ("Blast" the marrow). * **Paclitaxel:** Hypersensitivity reactions (pre-treat with dexamethasone/antihistamines) and neuropathy. * **Other M-phase inhibitors:** Ixabepilone (Epothilones) and Eribulin.

Question 420: Which of the following agents is not a proliferation-independent agent?

A. Vincristine (Correct Answer)
B. Carmustine
C. Melphalan
D. Cyclophosphamide

Explanation: ### Explanation Anticancer drugs are classified based on their relationship to the cell cycle into two categories: **Cell Cycle-Specific (CCS)** and **Cell Cycle-Nonspecific (CCNS)**. **1. Why Vincristine is the Correct Answer:** Vincristine is a **Cell Cycle-Specific (CCS)** agent. It belongs to the Vinca alkaloid class, which acts specifically during the **M-phase (Mitosis)** of the cell cycle. It binds to tubulin and inhibits its polymerization into microtubules, preventing the formation of the mitotic spindle. Because its efficacy is strictly dependent on the cell being in the process of division (proliferation), it is a **proliferation-dependent** agent. **2. Why the other options are incorrect:** * **Cyclophosphamide, Melphalan, and Carmustine:** These are all **Alkylating Agents**. Alkylating agents work by covalently bonding alkyl groups to DNA, leading to cross-linking and DNA strand breaks. This damage occurs regardless of whether the cell is actively dividing or in a resting state ($G_0$ phase). Therefore, they are classified as **Cell Cycle-Nonspecific (CCNS)** or **proliferation-independent** agents. ### NEET-PG High-Yield Pearls: * **M-Phase Specific Drugs:** Vinca alkaloids (Vincristine, Vinblastine) and Taxanes (Paclitaxel, Docetaxel). *Mnemonic: Vinca prevents assembly; Taxanes prevent disassembly.* * **S-Phase Specific Drugs:** Antimetabolites (Methotrexate, 5-FU, Cytarabine). * **$G_2$-Phase Specific Drugs:** Bleomycin. * **Dose-limiting toxicity of Vincristine:** Peripheral neuropathy (unlike Vinblastine, which is Bone Marrow Suppression). * **Carmustine/Lomustine:** Highly lipid-soluble nitrosoureas used primarily for brain tumors because they cross the blood-brain barrier.

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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