Anticancer Drugs — MCQs

Anticancer Drugs Indian Medical PG Practice Questions and MCQs

Question 231: Which of the following is an aromatase inhibitor used in breast cancer therapy?

A. Letrozole (Correct Answer)
B. Anastrozole
C. Exemestane
D. Tamoxifen

Explanation: **Explanation:** **Aromatase inhibitors (AIs)** are the mainstay of treatment for hormone receptor-positive (ER/PR+) breast cancer in **postmenopausal women**. In these patients, estrogen is primarily produced in peripheral tissues (fat, muscle, liver) by the conversion of adrenal androgens into estrogens via the enzyme **aromatase**. **1. Why Letrozole is correct:** Letrozole (along with Anastrozole) is a **Type II (Non-steroidal) Reversible Aromatase Inhibitor**. It competitively binds to the heme group of the cytochrome P450 subunit of the aromatase enzyme, effectively blocking the production of estrogen. It is highly potent and is often the first-line choice for adjuvant therapy or metastatic disease in postmenopausal women. **2. Analysis of Incorrect Options:** * **B & C (Anastrozole & Exemestane):** While both are indeed aromatase inhibitors, the question asks to identify "an" aromatase inhibitor. In many standardized exams like NEET-PG, if multiple correct drug classes are listed, the question often focuses on the most commonly used prototype or a specific distinction. However, technically, A, B, and C are all AIs. In a "single best answer" scenario, Letrozole is frequently highlighted as the prototype. * **D (Tamoxifen):** This is a **SERM (Selective Estrogen Receptor Modulator)**. It does not inhibit estrogen production; instead, it acts as a competitive antagonist at the estrogen receptor in breast tissue. It is the drug of choice for premenopausal women. **3. High-Yield Clinical Pearls for NEET-PG:** * **Classification:** * *Type I (Irreversible/Steroidal):* Exemestane. * *Type II (Reversible/Non-steroidal):* Letrozole, Anastrozole. * **Side Effects:** Unlike Tamoxifen, AIs do **not** cause uterine cancer or thromboembolism. However, they cause **decreased bone mineral density (osteoporosis)** and joint pain (arthralgia). * **Indication:** AIs are ineffective in premenopausal women because they cannot override the high estrogen production from the ovaries.

Question 232: Which of the following anticancer drugs can cause a hypercoagulable state?

A. 5-FU
B. L-asparaginase (Correct Answer)
C. Melphalan
D. Carmustine

Explanation: **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.

Question 233: What is the primary reason for administering mesna along with cyclophosphamide?

A. To increase absorption
B. To decrease excretion
C. To ameliorate hemorrhagic cystitis (Correct Answer)
D. To decrease metabolism

Explanation: **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 234: Imatinib used in CML acts by which mechanism?

A. Inhibiting BCR/ABL translocation tyrosine kinase
B. Blocking the action of P glycoprotein
C. Competitive inhibition of the ATP binding site of ABL kinase (Correct Answer)
D. C-Kit kinase inhibition

Explanation: **Explanation:** **1. Why Option C is Correct:** Imatinib is a selective small-molecule tyrosine kinase inhibitor (TKI). In Chronic Myeloid Leukemia (CML), the hallmark is the **Philadelphia chromosome (t[9;22])**, which creates the **BCR-ABL** fusion gene. This gene produces a constitutively active tyrosine kinase that drives uncontrolled cell proliferation. Imatinib works by **competitively binding to the ATP-binding site** of the ABL kinase domain. By blocking ATP from binding, the enzyme cannot phosphorylate its substrate, effectively "turning off" the signals for leukemic cell growth and inducing apoptosis. **2. Analysis of Incorrect Options:** * **Option A:** While Imatinib inhibits the *activity* of the BCR-ABL protein, it does **not** inhibit the translocation process itself (the genetic rearrangement). It targets the protein product after it has been formed. * **Option B:** P-glycoprotein is an efflux pump associated with multi-drug resistance. Imatinib is actually a *substrate* for P-glycoprotein (which can lead to resistance), but its primary therapeutic mechanism is not blocking this pump. * **Option C-Kit kinase inhibition:** While Imatinib **does** inhibit C-Kit (useful in Gastrointestinal Stromal Tumors - GIST), the question specifically asks for its mechanism in **CML**, where BCR-ABL inhibition is the primary driver. **3. High-Yield Clinical Pearls for NEET-PG:** * **Indications:** CML (First-line), GIST (targets C-Kit/CD117), and Hypereosinophilic syndrome (targets PDGFR). * **Adverse Effects:** Most characteristic is **periorbital edema** (fluid retention). Others include muscle cramps and GI upset. * **Resistance:** Most commonly occurs due to point mutations in the BCR-ABL kinase domain (e.g., **T315I mutation**). * **Next-Gen TKIs:** Dasatinib and Nilotinib are used if Imatinib resistance develops. Ponatinib is used specifically for the T315I mutation.

Question 235: Which of the following drugs is widely used in the management of carcinoma of the breast?

A. Actinomycin–D
B. Bleomycin
C. Doxorubicin (Correct Answer)
D. Dacarbazine

Explanation: **Explanation:** **Doxorubicin** (an Anthracycline antibiotic) is a cornerstone in the management of breast cancer. Its primary mechanism of action involves inhibiting **Topoisomerase II**, intercalating between DNA base pairs, and generating free radicals that cause DNA strand breaks. It is a key component of standard chemotherapy regimens such as **AC** (Adriamycin/Doxorubicin + Cyclophosphamide) and **FAC** (5-FU + Adriamycin + Cyclophosphamide). **Analysis of Incorrect Options:** * **Actinomycin–D (Dactinomycin):** Primarily used for pediatric solid tumors like **Wilms’ tumor**, Ewing’s sarcoma, and Rhabdomyosarcoma, as well as Gestational Choriocarcinoma. It is not a first-line agent for breast carcinoma. * **Bleomycin:** Known for causing pulmonary fibrosis, it is mainly used in **Germ cell tumors** (Testicular cancer), Hodgkin’s lymphoma, and squamous cell carcinomas of the head and neck. * **Dacarbazine:** An alkylating agent that is the drug of choice for **Malignant Melanoma** and is used in the ABVD regimen for Hodgkin’s Lymphoma. **High-Yield Clinical Pearls for NEET-PG:** * **Cardiotoxicity:** The most significant side effect of Doxorubicin is dose-dependent dilated cardiomyopathy. **Dexrazoxane** is an iron-chelating agent used to prevent this toxicity. * **Red Urine:** Doxorubicin can cause a harmless reddish discoloration of urine (not hematuria). * **Other Breast Cancer Drugs:** Remember that **Tamoxifen** (SERM) is used for ER/PR positive cases, and **Trastuzumab** is used for HER2/neu positive cases.

Question 236: All of the following immunosuppressives cause profound myelosuppression except?

A. Sirolimus
B. Cyclosporine (Correct Answer)
C. Azathioprine
D. Mercaptopurine

Explanation: ### Explanation The core concept in this question is distinguishing between **cytotoxic immunosuppressants** and **calcineurin inhibitors**. **Why Cyclosporine is the Correct Answer:** Cyclosporine is a **calcineurin inhibitor**. It works by binding to cyclophilin, which inhibits the phosphatase activity of calcineurin. This prevents the translocation of Nuclear Factor of Activated T-cells (NFAT), ultimately blocking the production of IL-2 and T-cell proliferation. Because its mechanism is highly specific to T-lymphocyte signaling and does not involve the inhibition of DNA synthesis or cell division in rapidly dividing cells, it is **not myelosuppressive**. Its primary toxicities are nephrotoxicity, gingival hyperplasia, and hirsutism. **Analysis of Incorrect Options:** * **Azathioprine & Mercaptopurine:** These are antimetabolites (purine analogs) that interfere with DNA synthesis. Since bone marrow cells are rapidly dividing, these drugs inherently cause significant **myelosuppression** (leukopenia and thrombocytopenia) as a primary side effect. * **Sirolimus (Rapamycin):** While it is not a calcineurin inhibitor (it is an mTOR inhibitor), it is well-known for causing **thrombocytopenia** and anemia as common side effects, making it more myelosuppressive than cyclosporine. **High-Yield NEET-PG Pearls:** * **Calcineurin Inhibitors (Cyclosporine, Tacrolimus):** Mnemonic for Cyclosporine side effects: **"6 H's"** — **H**ypertension, **H**yperlipidemia, **H**yperkalemia, **H**irsutism, **H**yperplasia of gums, and **H**epatotoxicity (plus Nephrotoxicity). * **Tacrolimus vs. Cyclosporine:** Tacrolimus is more potent and does *not* cause hirsutism or gingival hyperplasia (it may cause alopecia instead). * **Drug Interaction:** Azathioprine/6-MP levels increase dangerously when co-administered with **Allopurinol** (due to Xanthine Oxidase inhibition), leading to life-threatening bone marrow suppression.

Question 237: Which of the following blocks DNA replication by getting incorporated into the DNA strand?

A. Cytarabine (Correct Answer)
B. Nalidixic acid
C. Ciprofloxacin
D. Paclitaxel

Explanation: **Explanation:** **Correct Option: A. Cytarabine** Cytarabine (Ara-C) is a pyrimidine analog (antimetabolite) that acts specifically during the **S-phase** of the cell cycle. Its mechanism involves two primary steps: 1. It is phosphorylated intracellularly into its active form, **cytarabine triphosphate**. 2. This active form competes with deoxycytidine triphosphate to be **incorporated into the DNA strand**. Once incorporated, it acts as a DNA chain terminator and inhibits **DNA polymerase**, thereby blocking DNA synthesis and repair. **Incorrect Options:** * **B & C (Nalidixic acid and Ciprofloxacin):** These are Quinolone/Fluoroquinolone antibiotics. They inhibit **DNA Gyrase** (Topoisomerase II) and **Topoisomerase IV** in bacteria. They do not get incorporated into the DNA strand. * **D (Paclitaxel):** This is a Taxane that acts on microtubules. It **stabilizes microtubules** by preventing depolymerization (freezing them in the polymerized state), leading to cell cycle arrest in the **M-phase**. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Cytarabine is a cornerstone in the induction therapy of **Acute Myeloid Leukemia (AML)**. * **Specific Toxicity:** High-dose Cytarabine is associated with **Cerebellar toxicity** (ataxia, dysarthria) and **conjunctivitis** (prophylactic steroid drops are often used). * **Resistance:** Resistance to Cytarabine often occurs due to a decrease in the activating enzyme **deoxycytidine kinase**.

Question 238: Fulvestrant is used in the treatment of which of the following conditions?

A. HR positive metastatic breast cancer in postmenopausal women (Correct Answer)
B. Male breast cancer
C. Paget's disease
D. Acute myeloid leukemia associated with Down's syndrome

Explanation: **Fulvestrant** is a **Selective Estrogen Receptor Degrader (SERD)** [1], [2]. Unlike Selective Estrogen Receptor Modulators (SERMs) like Tamoxifen, which have agonist-antagonist effects, Fulvestrant is a pure estrogen receptor antagonist [2]. It binds to the estrogen receptor (ER), blocks estrogen binding, and triggers the rapid degradation of the receptor protein itself [1]. 1. **Why Option A is Correct:** Fulvestrant is specifically indicated for **Hormone Receptor (HR) positive metastatic breast cancer** in postmenopausal women, especially those who have progressed on prior anti-estrogen therapy (like Tamoxifen or Aromatase Inhibitors) [2]. By depleting the number of estrogen receptors, it effectively halts the growth of estrogen-dependent tumors [1]. 2. **Why Other Options are Incorrect:** * **Option B:** While Tamoxifen is the gold standard for male breast cancer, Fulvestrant is not the primary choice due to limited clinical data in men. * **Option C:** Paget’s disease of the bone is treated with Bisphosphonates (e.g., Zoledronate) or Calcitonin. * **Option D:** AML in Down’s syndrome is typically treated with Cytarabine-based chemotherapy regimens, not hormonal therapy. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** "Pure Antagonist" – it causes down-regulation of ER [1]. * **Administration:** It is administered via **intramuscular injection** (once monthly), unlike Tamoxifen which is oral [1]. * **Side Effects:** Hot flashes, injection site pain, and nausea. It does **not** increase the risk of endometrial cancer (unlike Tamoxifen) because it lacks agonist activity. * **Key Comparison:** Tamoxifen = SERM (Partial agonist); Fulvestrant = SERD (Pure antagonist) [2].

Question 239: Which of the following drugs is specifically for HER2-positive breast carcinoma?

A. Trastuzumab (Correct Answer)
B. Tamoxifen
C. Exemestane
D. Fulvestrant

Explanation: **Explanation:** **1. Why Trastuzumab is correct:** Trastuzumab is a **recombinant humanized monoclonal antibody** that specifically targets the extracellular domain of the **HER2/neu (ErbB2)** receptor. HER2 is a proto-oncogene (tyrosine kinase receptor) that is overexpressed in approximately 20–30% of breast cancer cases. By binding to this receptor, Trastuzumab inhibits cell proliferation and promotes antibody-dependent cellular cytotoxicity (ADCC), making it the gold standard for HER2-positive breast carcinoma. **2. Why the other options are incorrect:** * **Tamoxifen:** This is a **Selective Estrogen Receptor Modulator (SERM)**. It acts as an antagonist in the breast and is used for **ER/PR-positive** breast cancer, not specifically for HER2-positive cases. * **Exemestane:** This is an **Irreversible Aromatase Inhibitor (Type I)**. It works by blocking the peripheral conversion of androgens to estrogens. It is used in postmenopausal women with hormone-sensitive (ER+) breast cancer. * **Fulvestrant:** This is a **Selective Estrogen Receptor Downregulator (SERD)**. It binds to and degrades the estrogen receptor. It is used in advanced ER-positive breast cancer that has progressed after anti-estrogen therapy. **3. High-Yield Clinical Pearls for NEET-PG:** * **Cardiotoxicity:** The most significant side effect of Trastuzumab is **reversible cardiomyopathy** (decrease in LVEF). Unlike Doxorubicin, it does not cause structural damage (no myofibrillar dropout). * **Combination Warning:** Never co-administer Trastuzumab with Anthracyclines (like Doxorubicin) due to the high risk of synergistic cardiotoxicity. * **Other HER2 Drugs:** Lapatinib (dual TKI for EGFR/HER2) and Pertuzumab (inhibits HER2 dimerization) are also used in HER2+ cases.

Question 240: Which of the following is the most emetogenic anticancer drug?

A. Cisplatin (Correct Answer)
B. Carboplatin
C. High dose cyclophosphamide
D. High dose methotrexate

Explanation: **Explanation:** The emetogenicity of chemotherapy is categorized based on the percentage of patients who experience vomiting without antiemetic prophylaxis. **Cisplatin** is the prototype of **High Emetogenic Chemotherapy (HEC)**, with an emetic risk of >90%. **1. Why Cisplatin is the correct answer:** Cisplatin induces nausea and vomiting through two distinct pathways: * **Acute Phase (<24 hours):** Primarily due to the release of serotonin (5-HT) from enterochromaffin cells in the GI tract, stimulating 5-HT3 receptors. * **Delayed Phase (24–72 hours):** Primarily mediated by Substance P acting on Neurokinin-1 (NK1) receptors in the brainstem. Because it triggers both pathways intensely, it is considered the most emetogenic conventional agent. **2. Why the other options are incorrect:** * **Carboplatin:** While related to cisplatin, it is significantly less emetogenic (Moderate Emetogenic Risk, 30–90%) and has less renal and ototoxicity. * **High-dose Cyclophosphamide:** This is classified as HEC (especially >1500 mg/m²), but statistically, Cisplatin remains the gold standard for the highest emetic potential in clinical pharmacology. * **High-dose Methotrexate:** This is generally classified as having **Moderate to Low** emetogenic potential (30–60% risk). **3. Clinical Pearls for NEET-PG:** * **Drug of Choice for Cisplatin-induced vomiting:** A combination of a **5-HT3 antagonist** (e.g., Ondansetron), a **Corticosteroid** (Dexamethasone), and an **NK1 antagonist** (e.g., Aprepitant). * **Other HEC agents:** Dacarbazine, Mechlorethamine, and Streptozocin. * **Cisplatin Toxicity Profile:** Remember the mnemonic "3 Os" — **O**totoxicity, **O**ne (Nephrotoxicity), and **O**mited (Vomiting/Emesis). Amifostine is used to reduce cisplatin-induced nephrotoxicity.

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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