Anticancer Drugs Practice Questions

Q: Which of the following is NOT an alkylating agent?

Zalcitabine. The correct answer is **Zalcitabine**. **1. Why Zalcitabine is the correct answer:** Zalcitabine (ddC) is **not** an alkylating agent; it is a **Nucleoside Reverse Transcriptase Inhibitor (NRTI)** [1]. It is an antiretroviral drug used in the treatment of HIV/AIDS. It works by inhibiting the viral reverse transcriptase enzyme and causing DNA chain termination, rather than by cross-linking DNA strands like alkylating agents [1]. **2. Analysis of Incorrect Options (Alkylating Agents):** * **Cyclophosphamide:** A nitrogen mustard and the most widely used alkylating agent [2][3]. It is a prodrug activated by hepatic CYP450 to form phosphoramide mustard, which cross-links DNA [2][3]. * **Lomustine:** A member of the **Nitrosourea** family [3]. These are highly lipid-soluble alkylating agents that can cross the blood-brain barrier, making them first-line for brain tumors (e.g., glioblastoma). * **Busulfan:** An **Alkyl sulfonate**. It specifically targets the bone marrow and is frequently used in conditioning regimens before bone marrow transplantation. **3. NEET-PG High-Yield Clinical Pearls:** * **Cyclophosphamide:** Associated with **Hemorrhagic Cystitis** due to the metabolite **Acrolein** [2]. This is prevented by aggressive hydration and **MESNA**. * **Busulfan:** Known for causing **Pulmonary Fibrosis** ("Busulfan lung") and hyperpigmentation (Addisonian-like skin darkening). * **Nitrosoureas (Lomustine/Carmustine):** Unique for their CNS penetration; they are used for primary brain malignancies. * **Zalcitabine Side Effect:** The most significant dose-limiting toxicity is **peripheral neuropathy**.

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

Eye examination. **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.

Q: Which of the following causes peripheral neuritis?

Vincristine. **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).

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

All of the above. 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.

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

Gastrointestinal stromal tumors. **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].

Q: All of the following statements about methotrexate are true EXCEPT:

Folic acid reverses its toxic effects.. ### 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**.

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

Methotrexate. **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.

Q: Which of the following drugs cause metaphase arrest?

Vincristine, Paclitaxel, Colchicine. ### 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 1

Which of the following is NOT an alkylating agent?

Accepted Answer

Zalcitabine

Answer

Cyclophosphamide

Answer

Lomustine

Answer

Busulfan

Question 2

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

Accepted Answer

Hydroxyurea

Answer

Melphalan

Answer

Carmustine

Answer

Ifosfamide

Question 3

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

Accepted Answer

Eye examination

Answer

Liver function tests

Answer

Lung function tests

Answer

Hemogram

Question 4

Which of the following causes peripheral neuritis?

Accepted Answer

Vincristine

Answer

Methotrexate

Answer

Busulfan

Answer

Cyclophosphamide

Question 5

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

Accepted Answer

All of the above

Answer

Letrozole

Answer

Anastrozole

Answer

Tamoxifen

Question 6

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

Accepted Answer

Alkylating DNA, causing cross-links between parallel DNA strands

Answer

Blocking microtubular assembly and mitosis during M-phase

Answer

Inhibiting topoisomerase, preventing repair of DNA strand breaks

Answer

Intercalating in DNA strands, thereby preventing DNA replication by mRNA

Question 7

Imatinib is used in the treatment of which of the following conditions?

Accepted Answer

Gastrointestinal stromal tumors

Answer

Chronic myelomonocytic leukemia

Answer

Myelodysplastic syndrome

Answer

Acute lymphoblastic leukemia

Question 8

All of the following statements about methotrexate are true EXCEPT:

Accepted Answer

Folic acid reverses its toxic effects.

Answer

It is cell cycle specific and kills cells in the S phase.

Answer

Its toxicity primarily affects bone marrow and epithelial structures.

Answer

It is the drug of choice for choriocarcinoma.

Question 9

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

Accepted Answer

Methotrexate

Answer

6-Mercaptopurine

Answer

Thio-TEPA

Answer

Cytosine arabinoside

Question 10

Which of the following drugs cause metaphase arrest?

Accepted Answer

Vincristine, Paclitaxel, Colchicine

Answer

Griseofulvin, Vincristine, Paclitaxel

Answer

Griseofulvin, Paclitaxel, Etoposide

Answer

Vincristine, Etoposide, Colchicine

Anticancer Drugs — MCQs

Anticancer Drugs — MCQs

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