Anticancer Drugs Practice Questions

Q: What is the mechanism of action of imatinib mesylate?

Blocks the action of the chimeric fusion protein BCR-ABL.. **Explanation:** **1. Why Option C is Correct:** Imatinib mesylate is a revolutionary targeted therapy known as a **selective tyrosine kinase inhibitor (TKI)**. It specifically targets the **BCR-ABL** tyrosine kinase, a chimeric fusion protein resulting from the **Philadelphia chromosome (t[9;22])**. In Chronic Myeloid Leukemia (CML), this protein is constitutively active, leading to uncontrolled cell proliferation. Imatinib works by acting as a **competitive inhibitor at the ATP-binding site** of the BCR-ABL enzyme, preventing the phosphorylation of substrates and effectively "turning off" the oncogenic signal. **2. Why Other Options are Incorrect:** * **Options A & B:** P-glycoprotein (P-gp) is an efflux pump associated with multi-drug resistance (MDR) in cancer cells. While Imatinib is a substrate for P-gp (which can lead to drug resistance), its primary therapeutic mechanism of action is not the modulation of this protein. * **Option D:** Imatinib is a **competitive** inhibitor, not a non-competitive one. It competes directly with ATP for the binding pocket on the kinase domain. **3. NEET-PG High-Yield Clinical Pearls:** * **Drug of Choice (DOC):** Imatinib is the first-line treatment for **Chronic Myeloid Leukemia (CML)** and **Gastrointestinal Stromal Tumors (GIST)**. * **GIST Mechanism:** In GIST, it inhibits the **c-KIT (CD117)** tyrosine kinase. * **Other Targets:** It also inhibits the Platelet-Derived Growth Factor Receptor (**PDGFR**). * **Side Effects:** The most characteristic side effect is **periorbital edema** (fluid retention). Others include nausea, muscle cramps, and diarrhea. * **Resistance:** Resistance often develops due to point mutations in the BCR-ABL kinase domain (e.g., **T315I mutation**), which may require second-generation TKIs like **Dasatinib** or **Nilotinib**.

Q: High dose Methotrexate is used for the treatment of which of the following conditions?

Osteosarcoma. **Explanation:** **Methotrexate (MTX)** is a folate antagonist that inhibits the enzyme **dihydrofolate reductase (DHFR)**, leading to a depletion of intracellular folate pools and inhibition of DNA synthesis. **Why Osteosarcoma is correct:** High-dose Methotrexate (HDMTX), typically defined as doses >500 mg/m², is a cornerstone in the treatment of **Osteosarcoma**. Because osteosarcoma cells often have poor drug uptake or high levels of DHFR, massive doses are required to create a concentration gradient sufficient to bypass resistance mechanisms. This regimen necessitates **Leucovorin Rescue** (Folinic acid) to protect healthy cells from lethal hematological and GI toxicity. **Why other options are incorrect:** * **Rhabdomyosarcoma:** Primarily treated with the **VAC regimen** (Vincristine, Actinomycin-D, and Cyclophosphamide). * **Retinoblastoma:** Management usually involves local therapy or systemic chemotherapy using **VEC** (Vincristine, Etoposide, and Carboplatin). * **Ewing’s Sarcoma:** The standard protocol is the **VDC/IE regimen** (Vincristine, Doxorubicin, Cyclophosphamide alternating with Ifosfamide and Etoposide). **High-Yield Clinical Pearls for NEET-PG:** 1. **Leucovorin Rescue:** Must be started 24 hours after MTX to provide an alternative source of reduced folate for normal cells. 2. **Hydration & Alkalinization:** To prevent **nephrotoxicity** (MTX precipitates in acidic urine), patients must be hydrated and given sodium bicarbonate to keep urine pH >7.0. 3. **Glucarpidase:** An enzyme used as an antidote for MTX toxicity in patients with renal failure. 4. **Resistance:** Occurs via decreased polyglutamation, decreased uptake (reduced folate carrier), or gene amplification of DHFR.

Q: What is the primary effect of tamoxifen?

Increased risk of endometrial carcinoma. **Explanation:** Tamoxifen is a **Selective Estrogen Receptor Modulator (SERM)**. Its primary mechanism involves acting as a competitive antagonist at estrogen receptors in breast tissue, making it a cornerstone in the treatment of hormone receptor-positive breast cancer. **1. Why Option A is correct:** The "selective" nature of Tamoxifen means it acts as an **agonist** (estrogen-like effect) in certain tissues, specifically the **uterus** and bone. By stimulating the estrogen receptors in the endometrium, it promotes endometrial hyperplasia, which significantly increases the risk of **endometrial carcinoma**. This is a classic high-yield association for medical exams. **2. Why the other options are incorrect:** * **Option B:** Tamoxifen does not significantly decrease the risk of ovarian cancer; its primary protective role is in breast tissue. * **Option C:** Cardiotoxicity is a hallmark side effect of **Anthracyclines** (e.g., Doxorubicin) and **Trastuzumab**, not Tamoxifen. Tamoxifen is actually associated with a slightly increased risk of thromboembolism (DVT/PE). * **Option D:** Because Tamoxifen acts as an **agonist in bone**, it increases bone mineral density and actually **decreases the risk of osteoporosis** in postmenopausal women. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Tamoxifen is the DOC for breast cancer in **premenopausal** women. (Aromatase inhibitors are preferred in postmenopausal women). * **Side Effects:** Hot flashes (most common), venous thromboembolism, and endometrial cancer. * **Raloxifene:** Another SERM that is an antagonist in both breast and uterus; therefore, it does **not** increase the risk of endometrial cancer but is used primarily for osteoporosis.

Q: Which of the following agents inhibits microtubule formation?

Vincristine. **Explanation:** The correct answer is **Vincristine**. This question tests your understanding of drugs acting on the mitotic spindle (M-phase of the cell cycle). **1. Why Vincristine is Correct:** Vincristine belongs to the **Vinca Alkaloids** (derived from *Catharanthus roseus*). Its mechanism of action involves binding to **tubulin dimers**, which **prevents their polymerization** into microtubules. This inhibition of microtubule formation leads to "mitotic arrest" in the metaphase, eventually causing cell death. **2. Why the Other Options are Incorrect:** * **Paclitaxel:** While it also acts on microtubules, its mechanism is the opposite. It **promotes polymerization** and stabilizes microtubules, preventing their *disassembly* (de-polymerization). This creates "frozen" microtubules. * **Etoposide:** This is a **Topoisomerase II inhibitor**. It acts in the S and G2 phases by causing DNA strand breaks. * **Irinotecan:** This is a **Topoisomerase I inhibitor**, primarily used in colorectal cancer. It prevents the religation of single-strand DNA breaks. **3. High-Yield Clinical Pearls for NEET-PG:** * **Vincristine Side Effects:** Characterized by **Peripheral Neuropathy** (paresthesia, loss of reflexes) and paralytic ileus. Notably, it is **bone marrow sparing** (minimal myelosuppression). * **Vinblastine Side Effect:** Unlike Vincristine, its dose-limiting toxicity is **Bone Marrow Suppression** (*"Blast" blasts the bone marrow*). * **Taxanes (Paclitaxel):** Common side effects include peripheral neuropathy and hypersensitivity reactions (pre-medicate with steroids/antihistamines). * **Mnemonic:** **V**incristine **P**revents polymerization; **T**axanes **T**ighten (stabilize) the polymer.

Q: Which of the following drugs is used in the adjuvant setting for carcinoma of the colon?

Oxaliplatin. **Explanation:** **Oxaliplatin** is the correct answer because it is a cornerstone of **adjuvant chemotherapy** for Stage III (and high-risk Stage II) colon cancer. The standard adjuvant regimens are **FOLFOX** (5-Fluorouracil, Leucovorin, and Oxaliplatin) or **CAPOX** (Capecitabine and Oxaliplatin). Adjuvant therapy aims to eliminate micrometastases after surgical resection to reduce the risk of recurrence. **Analysis of Incorrect Options:** * **Bevacizumab (Option A):** This is a VEGF inhibitor (angiogenesis inhibitor). While highly effective in the **metastatic** (palliative) setting, clinical trials (like NSABP C-08) showed it provides no survival benefit in the adjuvant setting for colon cancer. * **Cetuximab (Option B):** An EGFR inhibitor used specifically for **metastatic** colorectal cancer in patients with **KRAS wild-type** tumors. Similar to Bevacizumab, it has failed to show benefit in adjuvant trials. * **Irinotecan (Option C):** A Topoisomerase I inhibitor. It is a key component of the **FOLFIRI** regimen used for **metastatic** disease. However, adding Irinotecan to adjuvant 5-FU (IFL regimen) did not improve outcomes compared to 5-FU alone and increased toxicity. **High-Yield Clinical Pearls for NEET-PG:** * **Dose-limiting toxicity of Oxaliplatin:** Peripheral sensory neuropathy (often triggered or exacerbated by **cold exposure**). * **Mechanism:** Platinum compound that forms intra-strand DNA cross-links. * **5-Fluorouracil (5-FU):** Always the "backbone" of colon cancer therapy; its action is enhanced by **Leucovorin** (folinic acid), which stabilizes the binding of 5-dUMP to thymidylate synthase. * **Microsatellite Instability (MSI-H):** Patients with Stage II colon cancer and MSI-H have a good prognosis and generally do *not* benefit from adjuvant 5-FU monotherapy.

Q: Thalidomide is used in the treatment of all EXCEPT:

Malaria. **Explanation:** Thalidomide is a potent immunomodulatory and anti-angiogenic drug. It acts by inhibiting **Tumor Necrosis Factor-alpha (TNF-α)** and modulating T-cell responses. While it was historically withdrawn due to severe teratogenicity, it has been repurposed for several specific clinical conditions. **Why Malaria is the correct answer:** Thalidomide has **no role** in the treatment of Malaria. Malaria is caused by *Plasmodium* parasites and requires antiprotozoal agents (like Artemisinin-based combination therapy or Chloroquine). Thalidomide does not possess any antiparasitic properties. **Analysis of other options:** * **Multiple Myeloma:** Thalidomide (often in combination with Dexamethasone) is a first-line agent. Its anti-angiogenic properties inhibit the blood supply to malignant plasma cells and induce apoptosis. * **DLE (Discoid Lupus Erythematosus):** Thalidomide is highly effective in refractory cases of DLE and cutaneous lupus due to its ability to suppress UV-induced TNF-α production in the skin. * **AML (Acute Myeloid Leukemia):** Though less common than its use in Myeloma, Thalidomide and its analogs (Lenalidomide) are used in certain subtypes of AML and Myelodysplastic Syndromes (MDS) to inhibit leukemic cell proliferation. **High-Yield Clinical Pearls for NEET-PG:** 1. **Teratogenicity:** The most famous side effect is **Phocomelia** (seal-like limbs). It is a Category X drug. 2. **Drug of Choice:** Thalidomide is the drug of choice for **Erythema Nodosum Leprosum (ENL)**, a Type 2 lepra reaction. 3. **Side Effects:** Apart from teratogenicity, it causes **peripheral neuropathy** (often irreversible) and increased risk of **thromboembolism**. 4. **Mechanism:** It binds to a protein called **Cereblon**, which is part of an E3 ubiquitin ligase complex.

Q: Which of the following anticancer drugs can cause a hypercoagulable state?

L-asparaginase. **Explanation:** **L-asparaginase** is the correct answer because its primary mechanism of action involves the depletion of asparagine, which is essential for protein synthesis in leukemic cells. However, this inhibition of protein synthesis is not selective and also affects the liver’s production of endogenous anticoagulants. Specifically, it leads to a significant **decrease in Protein C, Protein S, and Antithrombin III** levels. This deficiency shifts the hemostatic balance toward a **hypercoagulable state**, increasing the risk of venous thromboembolism (VTE) and sagittal sinus thrombosis. **Analysis of Incorrect Options:** * **A. 5-Fluorouracil (5-FU):** Primarily known for causing gastrointestinal toxicity (mucositis), myelosuppression, and a unique **hand-foot syndrome**. While it can cause cardiotoxicity (vasospasm), it is not classically associated with systemic hypercoagulability. * **C. Melphalan:** An alkylating agent (nitrogen mustard) used in multiple myeloma. Its dose-limiting toxicity is **bone marrow suppression**. * **D. Carmustine:** A nitrosourea that is highly lipid-soluble and crosses the blood-brain barrier. Its major toxicities include **delayed myelosuppression** and pulmonary fibrosis. **High-Yield Clinical Pearls for NEET-PG:** * **L-asparaginase** is a mainstay in **Acute Lymphoblastic Leukemia (ALL)** protocols. * **Key Side Effects:** Acute pancreatitis (high-yield), hyperglycemia (due to decreased insulin synthesis), and hypersensitivity reactions (anaphylaxis). * **Monitoring:** Patients on L-asparaginase should be monitored for signs of thrombosis and fibrinogen levels. * **Contrast:** While most anticancer drugs cause bleeding due to thrombocytopenia, L-asparaginase is unique for its **pro-thrombotic** potential.

Q: What is the primary reason for administering mesna along with cyclophosphamide?

To ameliorate hemorrhagic cystitis. **Explanation:** **1. Why Option C is Correct:** Cyclophosphamide and Ifosfamide are nitrogen mustards that are metabolized in the liver to form **Acrolein**, a toxic metabolite. Acrolein is excreted in the urine and causes direct irritation to the bladder mucosa, leading to **Hemorrhagic Cystitis** (characterized by hematuria and bladder pain). **Mesna** (2-MercaptoEthane Sulfonate Na) is a sulfhydryl compound that acts as a regional detoxifier. It concentrates in the bladder and reacts chemically with acrolein to form a non-toxic, water-soluble stable adduct, thereby preventing bladder damage. **2. Why Other Options are Incorrect:** * **Option A & D:** Mesna does not influence the pharmacokinetics (absorption or metabolism) of cyclophosphamide. Cyclophosphamide is a prodrug activated by hepatic CYP450 enzymes; Mesna does not interfere with this activation. * **Option B:** Mesna does not decrease the excretion of the drug. In fact, it is essential that both Mesna and the toxic metabolites are excreted together in the urine for the protective effect to occur. **3. High-Yield Clinical Pearls for NEET-PG:** * **Hydration:** Vigorous intravenous hydration is the first line of defense against hemorrhagic cystitis to dilute the acrolein. * **Ifosfamide:** While Mesna is optional for low-dose cyclophosphamide, it is **mandatory** when administering Ifosfamide due to higher acrolein production. * **Other Side Effects:** Apart from cystitis, cyclophosphamide is notorious for causing **SIADH** and **Alopecia**. * **Dose-Limiting Toxicity:** For cyclophosphamide, the dose-limiting toxicity is **Bone Marrow Suppression**.

Question 1

What is the mechanism of action of imatinib mesylate?

Accepted Answer

Blocks the action of the chimeric fusion protein BCR-ABL.

Answer

Increases the metabolism of P-glycoprotein.

Answer

Blocks the action of P-glycoprotein.

Answer

Non-competitive inhibition of the ATP binding site.

Question 2

High dose Methotrexate is used for the treatment of which of the following conditions?

Accepted Answer

Osteosarcoma

Answer

Rhabdomyosarcoma

Answer

Retinoblastoma

Answer

Ewing's sarcoma

Question 3

What is the primary effect of tamoxifen?

Accepted Answer

Increased risk of endometrial carcinoma

Answer

Decreased risk of ovarian cancer

Answer

Causes cardiotoxicity

Answer

Increased risk of osteoporosis

Question 4

A 55-year-old male patient complains of an abnormal growth on his right cheek. The patient has a history of tobacco chewing for 30 years. Radiologic findings reveal an 8x8 cm fungating mass invading the maxilla and mandible on the right side. Histologic findings are suggestive of squamous cell carcinoma. Which of the following statements regarding the treatment of this condition is NOT true?

Accepted Answer

Topoisomerase inhibitors promote the unwinding of parental DNA strands and prevent replication.

Answer

The drugs used are designed to block DNA replication.

Answer

Methotrexate and 5-fluorouracil block nucleotide synthesis.

Answer

The drugs used for cancer therapy inhibit the enzymes that participate in replication.

Question 5

Which of the following agents inhibits microtubule formation?

Accepted Answer

Vincristine

Answer

Paclitaxel

Answer

Etoposide

Answer

Irinotecan

Question 6

Which of the following drugs is used in the adjuvant setting for carcinoma of the colon?

Accepted Answer

Oxaliplatin

Answer

Bevacizumab

Answer

Cetuximab

Answer

Irinotecan

Question 7

Thalidomide is used in the treatment of all EXCEPT:

Accepted Answer

Malaria

Answer

Multiple myeloma

Answer

DLE

Answer

AML

Question 8

Which of the following is an aromatase inhibitor used in breast cancer therapy?

Accepted Answer

Letrozole

Answer

Anastrozole

Answer

Exemestane

Answer

Tamoxifen

Question 9

Which of the following anticancer drugs can cause a hypercoagulable state?

Accepted Answer

L-asparaginase

Answer

5-FU

Answer

Melphalan

Answer

Carmustine

Question 10

What is the primary reason for administering mesna along with cyclophosphamide?

Accepted Answer

To ameliorate hemorrhagic cystitis

Answer

To increase absorption

Answer

To decrease excretion

Answer

To decrease metabolism

Anticancer Drugs — MCQs

Anticancer Drugs — MCQs

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