Anticancer Drugs Practice Questions

Q: Which of the following drugs binds to tubulin and arrests the metaphase of the cell cycle?

Vincristine. **Explanation:** **Vincristine (Option A)** is the correct answer. It belongs to the **Vinca Alkaloids** class of antineoplastic agents. These drugs act as "spindle poisons" by binding specifically to **tubulin dimers**, preventing their polymerization into microtubules. This disruption prevents the formation of the mitotic spindle, leading to **cell cycle arrest in the Metaphase (M-phase)**. **Analysis of Incorrect Options:** * **Carmustine (Option B):** A Nitrosourea (Alkylating agent) that works by cross-linking DNA strands. It is cell-cycle non-specific and is notable for its high lipid solubility, allowing it to cross the blood-brain barrier (used in brain tumors). * **Infliximab (Option C):** A monoclonal antibody against **TNF-alpha**. It is used in the treatment of autoimmune conditions like Crohn’s disease and Rheumatoid Arthritis, not as a cytotoxic microtubule inhibitor. * **Methotrexate (Option D):** An Antimetabolite that inhibits **Dihydrofolate Reductase (DHFR)**. It interferes with DNA synthesis (S-phase) by depleting tetrahydrofolate levels. **High-Yield Clinical Pearls for NEET-PG:** * **Vinca Alkaloids (Vincristine, Vinblastine):** Prevent **assembly** (polymerization) of microtubules. * **Taxanes (Paclitaxel, Docetaxel):** Prevent **disassembly** (depolymerization) of microtubules; they "freeze" the spindle. * **Dose-Limiting Toxicity:** Vincristine is notorious for **Peripheral Neuropathy** (paresthesia, foot drop) but is relatively bone marrow-sparing. In contrast, Vinblastine is known for significant **Bone Marrow Suppression** ("Blast" = Bone marrow). * **Contraindication:** Vincristine must **never** be given intrathecally, as it is fatal (causes ascending myeloencephalopathy).

Q: Sodium 2-mercaptoethanesulfonate is used as a protective agent in:

Cancer chemotherapy. **Explanation:** **Sodium 2-mercaptoethanesulfonate (MESNA)** is a sulfhydryl compound used specifically as a cytoprotective agent in cancer chemotherapy to prevent **hemorrhagic cystitis**. **Why it is the correct answer:** Chemotherapeutic agents like **Cyclophosphamide** and **Ifosfamide** (oxazaphosphorines) are metabolized into **acrolein**, a highly reactive and toxic metabolite. Acrolein accumulates in the urinary bladder, causing irritation and sloughing of the bladder mucosa, leading to gross hematuria (hemorrhagic cystitis). MESNA works by concentrating in the urine, where its free thiol (-SH) group binds to and neutralizes acrolein, forming a non-toxic stable thioether. **Why other options are incorrect:** * **Radiotherapy:** While radioprotectors like *Amifostine* (a free radical scavenger) are used to protect salivary glands and lungs, MESNA has no role in mitigating radiation damage. * **Lithotripsy:** This is a procedure to break kidney stones; it does not involve chemical toxicity requiring a thiol-based protector. * **Hepatic encephalopathy:** This condition is managed with Lactulose, Rifaximin, or Neomycin to reduce ammonia levels, not MESNA. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** **M**ESNA **E**mpties **S**pecific **N**oxious **A**crolein. * **Hydration:** Vigorous intravenous hydration is always used alongside MESNA to further dilute acrolein. * **Ifosfamide vs. Cyclophosphamide:** MESNA is *mandatory* with Ifosfamide (due to higher acrolein production) but used with high-dose Cyclophosphamide. * **Other Protective Agents:** * **Dexrazoxane:** Prevents Doxorubicin-induced cardiotoxicity. * **Leucovorin (Folinic acid):** "Rescue" for Methotrexate toxicity. * **Amifostine:** Prevents Cisplatin-induced nephrotoxicity.

Q: A 50-year-old lady with severe rheumatoid disease causing joint pains and functional limitation is treated with methotrexate, requiring folinic rescue therapy. What is the mechanism by which methotrexate acts?

Binding to dihydrofolate reductase. **Explanation:** **Mechanism of Action (Correct Answer: C):** Methotrexate (MTX) is a folate antimetabolite. It acts by **competitively inhibiting the enzyme Dihydrofolate Reductase (DHFR)**. Under normal conditions, DHFR reduces dihydrofolate into tetrahydrofolate (THF), which is a crucial co-factor for the synthesis of thymidylate and purine nucleotides. By binding to DHFR with an affinity 1,000 times greater than the natural substrate, MTX depletes the cellular pool of THF, leading to a "thymineless death" of rapidly dividing cells. **Analysis of Incorrect Options:** * **Option A:** MTX does not increase folic acid excretion; it interferes with its intracellular metabolism. * **Option B:** DNA binding is the mechanism of Alkylating agents (e.g., Cyclophosphamide) or Antitumor antibiotics (e.g., Doxorubicin), not antimetabolites. * **Option D:** MTX **decreases** nucleotide synthesis by inhibiting the formation of precursors required for DNA and RNA production. **High-Yield Clinical Pearls for NEET-PG:** * **Folinic Acid (Leucovorin) Rescue:** As mentioned in the stem, Leucovorin is a reduced form of folate that bypasses the DHFR block. It is used to "rescue" normal cells from MTX toxicity (e.g., bone marrow suppression, mucositis). * **Resistance:** The most common mechanism of resistance to MTX is the production of **altered DHFR** with reduced affinity for the drug or decreased polyglutamation. * **Toxicity:** Watch for **Hepatotoxicity** (cirrhosis with long-term use in RA) and **Pulmonary fibrosis**. * **Drug Interaction:** NSAIDs and Penicillins decrease the renal excretion of MTX, increasing its toxicity.

Q: Which of the following anti-cancer drugs does not possess anti-inflammatory or immunosuppressive properties?

L-Asparaginase. **Explanation:** The correct answer is **L-Asparaginase**. **1. Why L-Asparaginase is correct:** L-Asparaginase is a unique enzyme used primarily in **Acute Lymphoblastic Leukemia (ALL)**. Its mechanism involves degrading circulating **L-asparagine** into aspartic acid and ammonia. Since leukemic cells lack the enzyme *asparagine synthetase*, they cannot synthesize asparagine endogenously and die due to protein synthesis inhibition. Unlike most cytotoxic drugs, L-Asparaginase is **not a general bone marrow suppressant** and does not interfere with the proliferation of normal T or B lymphocytes in a way that provides anti-inflammatory or immunosuppressive benefits. Its side effect profile is distinct, focusing on hypersensitivity, pancreatitis, and clotting factor deficiencies. **2. Why the other options are incorrect:** * **Methotrexate (MTX):** A folate antagonist that inhibits dihydrofolate reductase. It is a potent immunosuppressant and is the "gold standard" Disease-Modifying Antirheumatic Drug (DMARD) for **Rheumatoid Arthritis**. * **Azathioprine:** A purine antimetabolite (prodrug of 6-Mercaptopurine) that inhibits lymphocyte proliferation. It is widely used for **organ transplant rejection** and autoimmune conditions like SLE. * **Cyclophosphamide:** An alkylating agent that suppresses both B-cell and T-cell functions. It is used in severe autoimmune diseases like **Wegener’s Granulomatosis** and Lupus Nephritis. **3. NEET-PG High-Yield Pearls:** * **L-Asparaginase Toxicity:** Look for "Acute Pancreatitis" or "Thrombosis/Bleeding" (due to decreased synthesis of clotting factors and Antithrombin III) in clinical vignettes. * **Unique Property:** It is one of the few anticancer drugs that is **bone marrow sparing**. * **Resistance:** Occurs due to increased expression of asparagine synthetase by tumor cells.

Q: SIADH is caused by all of the following drugs except:

Actinomycin D. **Explanation:** The Syndrome of Inappropriate Antidiuretic Hormone (SIADH) is a common paraneoplastic syndrome, but it is also a well-documented side effect of several chemotherapeutic agents. **Why Actinomycin D is the correct answer:** Actinomycin D (Dactinomycin) is an antitumor antibiotic used primarily in pediatric tumors like Wilms' tumor and Ewing sarcoma. Unlike the other options listed, it is **not** associated with the induction of SIADH. Its primary dose-limiting toxicities are bone marrow suppression and gastrointestinal mucosal damage. **Analysis of incorrect options:** * **Vincristine & Vinblastine (Vinca Alkaloids):** These are classic causes of drug-induced SIADH. They are thought to exert a direct toxic effect on the neurohypophysis or the hypothalamic-neurohypophyseal tract, leading to the unregulated release of ADH. * **Cyclophosphamide:** This alkylating agent is a high-yield cause of SIADH, particularly when administered in high doses. It enhances the effect of ADH on the renal tubules. **Clinical Note:** This is particularly dangerous because patients receiving cyclophosphamide are often aggressively hydrated to prevent hemorrhagic cystitis, increasing the risk of severe hyponatremia. **NEET-PG High-Yield Pearls:** 1. **Common Drugs causing SIADH (Mnemonic: "S-S-C-V"):** **S**SRIs (Fluoxetine), **S**ulfonylureas (Chlorpropamide), **C**arbamazepine/Cyclophosphamide, and **V**inca Alkaloids. 2. **Management:** The mainstay of treatment for drug-induced SIADH is the discontinuation of the offending agent and fluid restriction. In chronic cases, **Demeclocycline** (an ADH antagonist) or **Tolvaptan** (V2 receptor antagonist) may be used. 3. **Diagnosis:** Look for hyponatremia, low serum osmolality, and inappropriately high urine osmolality in a normovolemic patient.

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

ALK positive Non-small cell carcinoma of lung. **Explanation:** **Crizotinib** is a first-generation tyrosine kinase inhibitor (TKI) that primarily targets the **ALK (Anaplastic Lymphoma Kinase)** protein. In approximately 3–5% of Non-Small Cell Lung Cancer (NSCLC) cases, a chromosomal rearrangement occurs (typically the EML4-ALK fusion gene), leading to constitutive activation of ALK signaling, which drives tumor growth. Crizotinib effectively inhibits this signaling pathway, making it the standard initial therapy for **ALK-positive NSCLC**. **Analysis of Incorrect Options:** * **Option A & C (FLT-3 positive):** FLT-3 mutations are hallmark drivers in **Acute Myeloid Leukemia (AML)**. The drugs used for FLT-3 positive AML include **Midostaurin** and **Gilteritinib**, not Crizotinib. * **Option D (BRCA-2 positive):** BRCA mutations involve DNA repair pathways. The treatment of choice for BRCA-positive metastatic breast or ovarian carcinoma involves **PARP inhibitors** such as **Olaparib** or **Niraparib**. **Clinical Pearls for NEET-PG:** * **Mechanism:** Crizotinib inhibits ALK, **ROS1**, and **c-MET** tyrosine kinases. * **Resistance:** Most patients eventually develop resistance to Crizotinib (often via the L1196M "gatekeeper" mutation). Second-generation ALK inhibitors like **Ceritinib**, **Alectinib**, and **Brigatinib** are used to overcome this. * **Side Effects:** Notable side effects include **visual disturbances** (flashes of light), hepatotoxicity, and QT interval prolongation. * **High-Yield Association:** Always associate **ALK rearrangement** with **younger age** and **non-smokers** in the context of lung adenocarcinoma.

Q: Amifostine protects all of the following organs, EXCEPT:

CNS. **Explanation:** **Amifostine** is a cytoprotective agent (a prodrug) that is converted by alkaline phosphatase into its active thiol metabolite, **WR-1065**. This metabolite acts as a potent scavenger of free radicals generated by cisplatin and radiation therapy, thereby protecting normal tissues from toxicity. **Why CNS is the correct answer:** Amifostine **does not cross the blood-brain barrier (BBB)**. Consequently, it cannot provide any protective effect to the Central Nervous System (CNS). This is a critical pharmacological limitation that makes it ineffective against neurotoxicity. **Analysis of incorrect options:** * **Kidneys:** Amifostine is FDA-approved to reduce cumulative **nephrotoxicity** associated with cisplatin in patients with advanced ovarian cancer. * **Salivary glands:** It is used to reduce the incidence of **xerostomia** (dry mouth) in patients undergoing post-operative radiation therapy for head and neck cancer. * **GIT:** It provides protection to the gastrointestinal mucosa against radiation-induced damage (proctitis/mucositis) and reduces bone marrow suppression (neutropenia). **High-Yield Clinical Pearls for NEET-PG:** * **Differential Uptake:** Amifostine protects normal cells more than tumor cells because normal cells have higher alkaline phosphatase activity and better vascularity, leading to higher concentrations of the active metabolite. * **Common Side Effect:** The most significant dose-limiting side effect of Amifostine is **hypotension** (seen in ~60% of patients), followed by nausea and vomiting. * **Drug Class:** It is specifically known as a **"Radioprotector."** * **Other Cytoprotectants to remember:** * **Mesna:** Prevents hemorrhagic cystitis (Cyclophosphamide/Ifosfamide). * **Dexrazoxane:** Prevents cardiotoxicity (Anthracyclines). * **Leucovorin:** Rescues bone marrow (Methotrexate).

Q: Which of the following statements about Cytarabine is false?

It is a purine analogue.. ### **Explanation** **1. Why Option D is the Correct Answer (The False Statement):** Cytarabine (Ara-C) is a **Pyrimidine analogue**, not a purine analogue. It is a deoxycytidine analogue that acts as an antimetabolite. Its mechanism involves being phosphorylated into its active form (Ara-CTP), which then competes with deoxycytidine triphosphate for incorporation into DNA. This inhibits **DNA polymerase**, leading to the termination of DNA chain elongation during the **S-phase** of the cell cycle. **2. Analysis of Other Options:** * **Option A (Short acting):** Cytarabine has a very short half-life (approximately 10–20 minutes) because it is rapidly deaminated by the enzyme **cytidine deaminase** into the inactive metabolite uracil arabinoside (Ara-U). * **Option B (Continuous IV infusion):** Due to its rapid metabolism and S-phase specificity, it must be administered via continuous intravenous infusion to ensure that cells entering the S-phase are consistently exposed to the drug. * **Option C (Cerebellar toxicity):** High-dose Cytarabine (HiDAC) can cross the blood-brain barrier. A classic and specific side effect is **cerebellar ataxia** (dysarthria, nystagmus, and dysmetria). **3. Clinical Pearls for NEET-PG:** * **Drug of Choice:** It is the backbone of the "7+3" induction regimen for **Acute Myeloid Leukemia (AML)**. * **Specific Side Effects:** Apart from cerebellar toxicity, it causes **conjunctivitis** (prophylactic steroid eye drops are used) and severe myelosuppression. * **Resistance:** Resistance often develops due to a decrease in the activating enzyme **deoxycytidine kinase**. * **Mnemonics:** Remember **"Cy-tarabine = Cy-tosine"** (Pyrimidine) and **"C for Cerebellum."**

Q: Which of the following is NOT a radiosensitizing drug?

Cyclophosphamide. **Radiosensitizers** are drugs that enhance the lethal effects of ionizing radiation on tumor cells. The correct answer is **Cyclophosphamide** because it is a cell-cycle non-specific alkylating agent that does not significantly sensitize cells to radiation; rather, it is typically used as a primary chemotherapeutic agent [1, 2, 3].**Why the other options are Radiosensitizers:** * **5-Fluorouracil (5-Fu):** An antimetabolite that inhibits thymidylate synthase. It sensitizes cells by depleting nucleotide pools and interfering with DNA repair mechanisms following radiation damage [1]. * **5-Bromo-2'-deoxyuridine (BUDR):** A halogenated pyrimidine analog that incorporates into DNA in place of thymidine. This makes the DNA strand more susceptible to breakage when exposed to radiation. * **Hydroxyurea:** This drug inhibits ribonucleotide reductase, arresting cells in the **G1-S phase**. Since cells are most sensitive to radiation in the late G1 and early S phases, it acts as a potent radiosensitizer.**High-Yield NEET-PG Pearls:**1. **Mechanism:** Radiosensitizers often work by increasing the production of free radicals or by inhibiting the repair of sublethal radiation damage.2. **Hypoxic Cell Sensitizers:** **Misonidazole** and **Nimorazole** are specific agents designed to mimic oxygen (the best natural radiosensitizer) in hypoxic tumor centers.3. **Gemcitabine** and **Cisplatin** are also clinically significant radiosensitizers used in concurrent chemoradiotherapy (e.g., in cervical or head and neck cancers).4. **Cell Cycle:** Remember that cells are most **radiosensitive** in the **M and G2 phases** and most **radioresistant** in the **S phase**.

Q: A patient undergoing treatment with R-CHOP chemotherapy for non-Hodgkin's lymphoma develops symmetric 'stocking and glove' type distal neuropathy, presenting as tingling in the hands and feet. If these symptoms are a side effect of the chemotherapy, which drug in the regimen is most likely responsible, and at which stage of the cell cycle does it cause arrest?

M phase. The patient is presenting with **peripheral neuropathy** (stocking-and-glove distribution), a classic dose-limiting toxicity of **Vincristine** [2, 3], which is the 'O' (Oncovin) in the **R-CHOP** regimen (Rituximab, Cyclophosphamide, Hydroxydaunorubicin/Doxorubicin, Oncovin, Prednisolone) [2]. Vincristine belongs to the **Vinca Alkaloids** class [1, 2]. These drugs work by binding to tubulin and **inhibiting microtubule polymerization** (preventing the formation of the mitotic spindle). Since the mitotic spindle is essential for chromosome separation, the cell cannot progress through mitosis, leading to **M phase arrest** [1, 2]. The neuropathy occurs because microtubules are also vital for axonal transport in neurons. ### 2. Why Incorrect Options are Wrong * **A & B (G1-S transition / S phase):** Drugs like **Antimetabolites** (e.g., Methotrexate, 5-Fluorouracil) act specifically during the S phase by inhibiting DNA synthesis. While Cyclophosphamide (in R-CHOP) is cell-cycle non-specific, its primary impact is on DNA cross-linking, not spindle formation. * **C (G2-M transition):** This is the site of action for **Bleomycin** (which causes G2 arrest) and sometimes Etoposide. These do not typically cause the symmetric peripheral neuropathy described. ### 3. NEET-PG High-Yield Pearls * **Vincristine vs. Vinblastine:** Remember the mnemonic: **"Vincristine blasts the Nerves (Neurotoxicity); Vinblastine blasts the Marrow (Bone marrow suppression)."** [3] * **Taxanes (Paclitaxel):** Also act on the **M phase** but via the opposite mechanism—they **hyper-stabilize** microtubules (inhibiting *depolymerization*) [3]. * **R-CHOP Side Effects:** * **D**oxorubicin: Cardiotoxicity (Dilated Cardiomyopathy). * **C**yclophosphamide: Hemorrhagic cystitis (prevented by **MESNA**). * **V**incristine: Peripheral neuropathy and paralytic ileus [2, 3].

Question 1

Which of the following drugs binds to tubulin and arrests the metaphase of the cell cycle?

Accepted Answer

Vincristine

Answer

Carmustine

Answer

Infliximab

Answer

Methotrexate

Question 2

Sodium 2-mercaptoethanesulfonate is used as a protective agent in:

Accepted Answer

Cancer chemotherapy

Answer

Radiotherapy

Answer

Lithotripsy

Answer

Hepatic encephalopathy

Question 3

A 50-year-old lady with severe rheumatoid disease causing joint pains and functional limitation is treated with methotrexate, requiring folinic rescue therapy. What is the mechanism by which methotrexate acts?

Accepted Answer

Binding to dihydrofolate reductase

Answer

Increasing folic acid excretion

Answer

DNA binding

Answer

Increasing nucleotide synthesis

Question 4

Which of the following anti-cancer drugs does not possess anti-inflammatory or immunosuppressive properties?

Accepted Answer

L-Asparaginase

Answer

Methotrexate

Answer

Azathioprine

Answer

Cyclophosphamide

Question 5

SIADH is caused by all of the following drugs except:

Accepted Answer

Actinomycin D

Answer

Vincristine

Answer

Vinblastine

Answer

Cyclophosphamide

Question 6

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

Accepted Answer

ALK positive Non-small cell carcinoma of lung

Answer

FLT-3 positive Non-small cell carcinoma of lung

Answer

FLT-3 positive Acute myeloid leukemia

Answer

BRCA-2 positive metastatic breast carcinoma

Question 7

Amifostine protects all of the following organs, EXCEPT:

Accepted Answer

CNS

Answer

GIT

Answer

Kidneys

Answer

Salivary glands

Question 8

Which of the following statements about Cytarabine is false?

Accepted Answer

It is a purine analogue.

Answer

It is very short acting.

Answer

It is given as continuous IV infusion.

Answer

It can lead to cerebellar toxicity.

Question 9

Which of the following is NOT a radiosensitizing drug?

Accepted Answer

Cyclophosphamide

Answer

5-Fluorouracil (5-Fu)

Answer

5-Bromo-2'-deoxyuridine (BUDR)

Answer

Hydroxyurea

Question 10

A patient undergoing treatment with R-CHOP chemotherapy for non-Hodgkin's lymphoma develops symmetric 'stocking and glove' type distal neuropathy, presenting as tingling in the hands and feet. If these symptoms are a side effect of the chemotherapy, which drug in the regimen is most likely responsible, and at which stage of the cell cycle does it cause arrest?

Accepted Answer

M phase

Answer

G1-S transition

Answer

S phase

Answer

G2-M transition

Anticancer Drugs — MCQs

Anticancer Drugs — MCQs

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