Anticancer Drugs Practice Questions

Q: What is the only FDA-approved radioactive antibody that can be used for the treatment of lymphoma?

Ibritumomab. **Explanation:** **Correct Answer: B. Ibritumomab** The correct answer is **Ibritumomab tiuxetan**. This is a radioimmunotherapy agent consisting of a monoclonal antibody (targeting the **CD20** antigen on B-cells) conjugated to a chelator (tiuxetan) that carries a radioactive isotope, typically **Yttrium-90 ($^{90}$Y)**. It works by delivering targeted beta-radiation directly to malignant B-cells in Non-Hodgkin Lymphoma (NHL), causing DNA damage to both the bound cell and neighboring tumor cells (the "bystander effect"). **Analysis of Incorrect Options:** * **A. Trastuzumab:** A monoclonal antibody targeting the **HER2/neu** receptor. It is used primarily in HER2-positive breast and gastric cancers. It is not radioactive. * **C. Rituximab:** A chimeric monoclonal antibody against **CD20**. While it is the "parent" antibody for many lymphoma treatments, it is a non-radioactive immunotherapy that works via ADCC (Antibody-Dependent Cellular Cytotoxicity) and complement activation. * **D. Imatinib:** A small molecule **Tyrosine Kinase Inhibitor (TKI)** targeting BCR-ABL, c-KIT, and PDGFR. It is the first-line oral treatment for Chronic Myeloid Leukemia (CML) and GIST, not an antibody. **High-Yield Clinical Pearls for NEET-PG:** * **Radioisotope:** Ibritumomab is most commonly linked with **Yttrium-90** (pure beta emitter). * **Tositumomab:** Another radioactive antibody (linked to Iodine-131) was previously FDA-approved but has been discontinued from the market. * **Target:** All "mabs" ending in "-ximab" or "-mumab" used in lymphoma generally target **CD20**. * **Side Effect:** The dose-limiting toxicity for Ibritumomab is **myelosuppression** (thrombocytopenia and neutropenia) due to the systemic effects of the radiation.

Q: Leucovorin rescue is related to which of the following?

Methotrexate toxicity. **Explanation:** **Leucovorin (Folinic Acid)** is a reduced form of folic acid. Its primary role in oncology is to bypass the metabolic block created by **Methotrexate (MTX)**. 1. **Why Methotrexate is the correct answer:** Methotrexate acts by inhibiting the enzyme **Dihydrofolate Reductase (DHFR)**, which prevents the conversion of folic acid to its active form, Tetrahydrofolate (THF). This depletion of THF halts DNA synthesis, leading to cell death. Leucovorin does not require DHFR for activation; it provides a direct source of reduced folate to healthy cells, "rescuing" them from lethal toxicity. This is typically administered 24 hours after high-dose MTX to prevent bone marrow suppression and GI mucosal damage. 2. **Why other options are incorrect:** * **Cyclophosphamide:** Toxicity (Hemorrhagic Cystitis) is managed with **MESNA** and aggressive hydration. * **Oncovin (Vincristine):** Toxicity (Peripheral Neuropathy) is managed symptomatically; there is no specific "rescue" agent. * **Cisplatin:** Nephrotoxicity is managed with **Amifostine** and vigorous hydration with chloride diuresis. **High-Yield Clinical Pearls for NEET-PG:** * **The "Leucovorin Potentiation":** While Leucovorin *rescues* cells from MTX, it actually *enhances* the activity 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 breaks down MTX. * **Mnemonic for MTX side effects:** **M**yelosuppression, **T**eratogenic, **X**-tra (Mucositis/Liver Cirrhosis).

Q: Hand, foot, and mouth syndrome is caused by which of the following?

5-Fluorouracil. **Explanation:** **Hand-Foot Syndrome (HFS)**, also known as Palmar-Plantar Erythrodysesthesia (PPE), is a distinct dermatological toxicity characterized by redness, swelling, and pain on the palms and soles. 1. **Why 5-Fluorouracil (5-FU) is correct:** 5-FU and its oral prodrug, **Capecitabine**, are the most common causes of HFS. The underlying mechanism involves the leakage of the drug from small capillaries in the palms and soles due to high pressure and friction. Once leaked, the drug causes local tissue damage. Capecitabine is actually more frequently associated with this syndrome than bolus 5-FU. 2. **Why other options are incorrect:** * **Cisplatin:** Primarily known for its "C" toxicities: **C**ytotoxicity (Ototoxicity) and **C**idney (Nephrotoxicity). It is also highly emetogenic. * **Methotrexate:** Its hallmark toxicities include myelosuppression, mucositis, and hepatotoxicity. It is managed with Leucovorin rescue. * **Methysergide:** This is an ergot alkaloid used for migraine prophylaxis, not an anticancer drug. Its classic side effect is **retroperitoneal fibrosis**. **High-Yield Clinical Pearls for NEET-PG:** * **Management of HFS:** Dose reduction or interruption of the drug is the primary treatment. Supportive care includes urea-based creams and avoiding heat/friction. * **5-FU Toxicity:** Aside from HFS, 5-FU is notorious for causing **mucositis** and diarrhea. * **DPD Deficiency:** Patients with Dihydropyrimidine Dehydrogenase (DPD) deficiency are at a high risk of severe, life-threatening toxicity when given 5-FU. * **Other drugs causing HFS:** Sorafenib, Sunitinib, and Cytarabine.

Q: Which of the following are anticancer drugs of plant origin?

Vincristine and Isotretinoin. **Explanation:** The correct answer is **D (Vincristine and Isotretinoin)** because both drugs are derived from natural plant sources and used in oncology. 1. **Vincristine:** This is a classic **Vinca alkaloid** derived from the Madagascar periwinkle plant (*Catharanthus roseus*). It acts as a cell-cycle specific agent (M-phase) by binding to tubulin and inhibiting microtubule polymerization, thereby preventing spindle formation. 2. **Isotretinoin:** While often associated with dermatology, Isotretinoin (13-cis-retinoic acid) is a **Retinoid**, which is a derivative of **Vitamin A**. Vitamin A is naturally sourced from plant carotenoids (like beta-carotene). In oncology, it is used as a differentiating agent, particularly in the treatment of high-risk neuroblastoma and certain skin cancers. **Analysis of Incorrect Options:** * **Bleomycin (Option A):** This is an antitumor antibiotic. It is derived from the fungus-like bacterium ***Streptomyces verticillus***, not a plant. * **Isotretinoin alone (Option B/C):** While correct in origin, these options are incomplete as Vincristine also fits the criteria. **High-Yield NEET-PG Pearls:** * **Plant-Derived Anticancer Groups:** * **Vinca Alkaloids:** Vincristine, Vinblastine (Source: *Catharanthus roseus*). * **Taxanes:** Paclitaxel, Docetaxel (Source: *Taxus brevifolia/baccata*). * **Epipodophyllotoxins:** Etoposide, Teniposide (Source: *Podophyllum peltatum*). * **Camptothecins:** Irinotecan, Topotecan (Source: *Camptotheca acuminata*). * **Side Effect Note:** Vincristine is notorious for **peripheral neuropathy** (paresthesia, foot drop) but is relatively **bone marrow sparing**, unlike Vinblastine.

Q: What enzyme is inhibited by etoposide?

Topoisomerase II. **Explanation:** **Correct Answer: B. Topoisomerase II** Etoposide (and its analog Teniposide) is a semi-synthetic derivative of podophyllotoxin. Its primary mechanism of action involves inhibiting **Topoisomerase II**. This enzyme is responsible for creating transient double-stranded breaks in DNA to relieve torsional strain during replication. Etoposide binds to the DNA-topoisomerase II complex, preventing the religation of these breaks. This leads to permanent DNA strand scission, triggering apoptosis. It is cell-cycle specific, acting primarily in the **late S and G2 phases**. **Analysis of Incorrect Options:** * **A. Topoisomerase I:** This enzyme creates single-stranded breaks. It is inhibited by the **Camptothecins** (e.g., Irinotecan and Topotecan). * **C. Dihydrofolate Reductase (DHFR):** This enzyme is inhibited by **Methotrexate**, which prevents the conversion of dihydrofolate to tetrahydrofolate, disrupting thymidylate synthesis. * **D. Dihydroorotate Oxidase:** This mitochondrial enzyme is involved in de novo pyrimidine synthesis and is inhibited by **Leflunomide** (used in Rheumatoid Arthritis). **High-Yield Clinical Pearls for NEET-PG:** * **Indications:** Etoposide is a cornerstone in treating Small Cell Lung Cancer (SCLC), testicular tumors (as part of the BEP regimen), and lymphomas. * **Adverse Effects:** Apart from myelosuppression, a high-yield side effect is **secondary leukemia** (specifically Acute Myeloid Leukemia with 11q23 translocation), which typically occurs 2–3 years after treatment. * **Mnemonic:** Remember "**E**-**T**-**O**-poside" inhibits Topoisomerase **TWO** (II).

Q: Which drug is used in estrogen-dependent breast cancer?

Tamoxifen. **Tamoxifen** is the gold standard for treating estrogen receptor-positive (ER+) breast cancer [1]. It belongs to the class of **Selective Estrogen Receptor Modulators (SERMs)** [2]. Its mechanism of action is tissue-specific: it acts as a competitive **antagonist** in breast tissue, blocking estrogen from binding to its receptor, thereby inhibiting the growth of estrogen-dependent tumor cells [1]. **Analysis of Incorrect Options:** * **Clomiphene citrate:** While also a SERM, it acts primarily as an antagonist at the hypothalamus. This blocks the negative feedback of estrogen, leading to increased FSH/LH secretion. It is used for **ovulation induction** in infertility, not breast cancer [2]. * **Estrogen:** Administering estrogen would stimulate the growth of estrogen-dependent tumors, worsening the prognosis. * **Adriamycin (Doxorubicin):** This is a potent cytotoxic antibiotic (anthracycline) used in many cancers. While used in breast cancer chemotherapy (AC regimen), it is **not specific** to estrogen-dependent pathways; it works via DNA intercalation and topoisomerase II inhibition. **NEET-PG High-Yield Pearls:** * **Dual Nature:** Tamoxifen is an antagonist in the breast but an **agonist in the endometrium and bone** [2]. * **Side Effects:** Due to its agonistic effect on the uterus, it increases the risk of **endometrial carcinoma**. It also increases the risk of thromboembolism (DVT/PE) [1]. * **Prophylaxis:** It is used for both treatment and primary prevention of breast cancer in high-risk women [1]. * **Drug of Choice:** For post-menopausal ER+ breast cancer, **Aromatase Inhibitors** (e.g., Letrozole, Anastrozole) are now often preferred over Tamoxifen [1].

Q: Hemorrhagic cystitis is a known side effect of which of the following medications?

Cyclophosphamide. **Explanation:** **Cyclophosphamide** (and its analog Ifosfamide) is an alkylating agent of the nitrogen mustard group. It is a prodrug metabolized in the liver to form two active metabolites: **Aldophosphamide** and **Phosphoramide mustard**. During this process, a toxic byproduct called **Acrolein** is generated. Acrolein is excreted in the urine, where it causes direct irritation and sloughing of the bladder mucosa, leading to **hemorrhagic cystitis**. **Analysis of Incorrect Options:** * **B. Busulfan:** An alkylating agent primarily used in CML. Its classic side effects include pulmonary fibrosis ("Busulfan lung"), hyperpigmentation, and adrenal insufficiency-like syndrome. * **C. Ketoprofen:** A non-steroidal anti-inflammatory drug (NSAID). While it can cause renal impairment or gastric ulcers, it is not associated with hemorrhagic cystitis. * **D. 5-Fluorouracil:** An antimetabolite (pyrimidine analog). Its hallmark side effects include hand-foot syndrome, myelosuppression, and mucositis. **NEET-PG High-Yield Pearls:** 1. **Prevention:** Hemorrhagic cystitis is prevented by aggressive hydration and the administration of **MESNA** (2-Mercaptoethane Sulfonate Na). 2. **Mechanism of MESNA:** It contains a thiol (-SH) group that binds to and neutralizes acrolein in the bladder, forming a non-toxic compound. 3. **Other Cyclophosphamide Side Effects:** It is notorious for causing SIADH and is a potent immunosuppressant. 4. **Long-term Risk:** Chronic irritation from acrolein increases the risk of **Transitional Cell Carcinoma** of the bladder.

Q: Which tyrosine kinase inhibitor has HER2/NEU receptor inhibition activity?

Lapatinib. **Explanation:** **Lapatinib** is a dual tyrosine kinase inhibitor (TKI) that targets both the **Epidermal Growth Factor Receptor (EGFR/ErbB1)** and the **Human Epidermal Growth Factor Receptor 2 (HER2/neu/ErbB2)**. Unlike monoclonal antibodies like Trastuzumab which bind to the extracellular domain, Lapatinib acts intracellularly to inhibit the ATP-binding domain of these receptors. It is primarily used in the treatment of HER2-positive advanced or metastatic breast cancer. **Analysis of Incorrect Options:** * **Imatinib:** The first-line TKI for Chronic Myeloid Leukemia (CML). It targets **BCR-ABL**, c-KIT, and PDGFR. It has no activity against HER2. * **Nilotinib:** A second-generation TKI designed to overcome Imatinib resistance in CML. Like Imatinib, its primary target is the **BCR-ABL** tyrosine kinase. * **Sunitinib:** A multi-targeted TKI that primarily inhibits **VEGFR** and PDGFR. It is used in Renal Cell Carcinoma (RCC) and Gastrointestinal Stromal Tumors (GIST) due to its potent anti-angiogenic properties. **High-Yield Clinical Pearls for NEET-PG:** * **Lapatinib vs. Trastuzumab:** Lapatinib is small enough to cross the **blood-brain barrier**, making it useful for CNS metastases in HER2+ breast cancer, where Trastuzumab (a large antibody) has limited penetration. * **Side Effects:** A common side effect of Lapatinib is a skin rash (common to EGFR inhibitors) and diarrhea. * **Other HER2 Inhibitors:** **Neratinib** and **Afatinib** are irreversible ErbB family blockers. * **Drug of Choice:** Imatinib remains the DOC for CML and GIST (c-KIT positive).

Q: Which drug is used to counteract Methotrexate toxicity?

Folinic acid. **Explanation:** **Mechanism of Action & Correct Answer:** Methotrexate (MTX) is an antimetabolite that acts as a folic acid antagonist. It competitively inhibits the enzyme **Dihydrofolate Reductase (DHFR)**, preventing the conversion of Dihydrofolate (DHF) to Tetrahydrofolate (THF). THF is essential for DNA synthesis (purine and thymidine synthesis). **Folinic acid (Leucovorin)** is the correct answer because it is a reduced form of folic acid (5-formyl THF). Unlike regular folic acid, it does **not** require DHFR for activation. It bypasses the blocked enzyme to provide the necessary folate pool for healthy cells, a process known as **"Leucovorin Rescue."** **Analysis of Incorrect Options:** * **Folic acid:** Ineffective because MTX inhibits DHFR, the very enzyme needed to convert folic acid into its active form. * **Mesna:** Used specifically to prevent hemorrhagic cystitis caused by Cyclophosphamide and Ifosfamide by neutralizing acrolein in the bladder. * **Vitamin B12:** While involved in DNA synthesis, it does not counteract the DHFR inhibition caused by MTX. **High-Yield Clinical Pearls for NEET-PG:** 1. **Timing:** Leucovorin must be administered within 24–42 hours of MTX to be effective. 2. **Glucarpidase:** An alternative "rescue" agent used in patients with MTX-induced renal failure; it enzymatically breaks down MTX. 3. **Toxicity Profile:** MTX toxicity typically manifests as myelosuppression, mucositis, and hepatotoxicity. 4. **Resistance:** MTX resistance often occurs via decreased polyglutamation or altered DHFR affinity.

Question 1

What is the only FDA-approved radioactive antibody that can be used for the treatment of lymphoma?

Accepted Answer

Ibritumomab

Answer

Trastuzumab

Answer

Rituximab

Answer

Imatinib

Question 2

Leucovorin rescue is related to which of the following?

Accepted Answer

Methotrexate toxicity

Answer

Cyclophosphamide toxicity

Answer

Oncovin toxicity

Answer

Cisplatin toxicity

Question 3

Hand, foot, and mouth syndrome is caused by which of the following?

Accepted Answer

5-Fluorouracil

Answer

Cisplatin

Answer

Methotrexate

Answer

Metvcergide

Question 4

Which of the following are anticancer drugs of plant origin?

Accepted Answer

Vincristine and Isotretinoin

Answer

Vincristine and Bleomycin

Answer

Vincristine

Answer

Isotretinoin

Question 5

What enzyme is inhibited by etoposide?

Accepted Answer

Topoisomerase II

Answer

Topoisomerase I

Answer

Dihydrofolate reductase

Answer

Dihydroorotate oxidase

Question 6

Which drug is used in estrogen-dependent breast cancer?

Accepted Answer

Tamoxifen

Answer

Clomiphene citrate

Answer

Estrogen

Answer

Adriamycin

Question 7

Hemorrhagic cystitis is a known side effect of which of the following medications?

Accepted Answer

Cyclophosphamide

Answer

Busulfan

Answer

Ketoprofen

Answer

5-Fluorouracil

Question 8

What is the most common side effect of 5-fluorouracil?

Accepted Answer

Gastrointestinal toxicity

Answer

Bone marrow depression

Answer

Cardiotoxicity

Answer

Neurotoxicity

Question 9

Which tyrosine kinase inhibitor has HER2/NEU receptor inhibition activity?

Accepted Answer

Lapatinib

Answer

Imatinib

Answer

Nilotinib

Answer

Sunitinib

Question 10

Which drug is used to counteract Methotrexate toxicity?

Accepted Answer

Folinic acid

Answer

Mesna

Answer

Folic acid

Answer

Vitamin B12

Anticancer Drugs — MCQs

Anticancer Drugs — MCQs

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