Anticancer Drugs Practice Questions

Q: A 42-year-old female with acute lymphoblastic leukemia is being treated with a multi-drug chemotherapy protocol. On day 3 of treatment, she develops confusion, seizures, and laboratory investigations show: serum uric acid 12 mg/dL, potassium 6.2 mEq/L, phosphate 7.8 mg/dL, calcium 6.5 mg/dL, and creatinine 2.8 mg/dL. She was given allopurinol prophylaxis before starting chemotherapy. Which agent would have been more effective in preventing this complication?

Rasburicase administered before chemotherapy initiation. ***Rasburicase administered before chemotherapy initiation*** - **Rasburicase** is a recombinant **urate oxidase** enzyme that converts existing **uric acid** into **allantoin**, which is 5-10 times more soluble and easily excreted by the kidneys. - It is significantly more effective than allopurinol for **high-risk Tumor Lysis Syndrome (TLS)** because it eliminates the current uric acid burden rather than just preventing new synthesis. *Febuxostat at higher doses* - Like allopurinol, **febuxostat** is a **xanthine oxidase inhibitor** that only prevents the formation of new uric acid and does not degrade existing levels. - It is not recommended as a replacement for rasburicase in cases or high-risk scenarios involving **acute kidney injury** and severe **hyperuricemia**. *Probenecid with increased hydration* - **Probenecid** is a **uricosuric** that increases uric acid excretion, which significantly increases the risk of **uric acid crystal precipitation** in the renal tubules during TLS. - It is contraindicated in this setting as it can exacerbate **obstructive uropathy** and worsen the patient's rising **creatinine**. *Sodium bicarbonate for urinary alkalinization* - **Urinary alkalinization** is often avoided in TLS because it promotes the precipitation of **calcium phosphate crystals** in the kidneys. - In patients with severe **hyperphosphatemia**, as seen here, alkalinization increases the risk of **metastatic calcification** and causes a further drop in **serum calcium**.

Q: Which drug is used exclusively in organ transplantation and autoimmune diseases, but not in cancers?

Cyclosporine. **Explanation:** The correct answer is **Cyclosporine**. **1. Why Cyclosporine is correct:** Cyclosporine is a **calcineurin inhibitor** that selectively inhibits T-cell activation by blocking the production of Interleukin-2 (IL-2). Unlike traditional cytotoxic drugs, it does not interfere with DNA synthesis or cause bone marrow suppression. Because it lacks direct anti-proliferative activity against malignant cells, it has **no role in cancer chemotherapy**. Its clinical utility is strictly limited to preventing graft rejection in organ transplantation and managing severe autoimmune conditions (e.g., Psoriasis, Rheumatoid Arthritis). **2. Why other options are incorrect:** * **Cyclophosphamide (Option A):** An alkylating agent used for both cancers (Lymphomas, Breast cancer) and autoimmune diseases (SLE, Wegener’s). * **Methotrexate (Option B):** A folate antagonist used in high doses for malignancies (Osteosarcoma, ALL) and in low doses for autoimmune conditions (RA, Psoriasis). * **6-Mercaptopurine (Option D):** A purine analogue primarily used in the maintenance therapy of Acute Lymphoblastic Leukemia (ALL) and also in Inflammatory Bowel Disease (IBD). **3. High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Cyclosporine binds to **Cyclophilin**, forming a complex that inhibits Calcineurin. * **Side Effects:** "The 4 H's" — **H**ypertension, **H**irsutism, **H**yperplasia of gums (Gingival Hyperplasia), and **H**yperlipidemia. * **Dose-limiting toxicity:** Nephrotoxicity (afferent arteriolar vasoconstriction). * **Metabolism:** Metabolized by **CYP3A4**; avoid grapefruit juice as it increases drug levels. * **Tacrolimus:** Another calcineurin inhibitor (binds to FKBP-12) that is more potent than Cyclosporine but does *not* cause hirsutism or gingival hyperplasia.

Q: Tamoxifen is useful in which of the following conditions?

Estrogen receptor-positive breast carcinoma. **Explanation:** **Tamoxifen** is the prototype **Selective Estrogen Receptor Modulator (SERM)**. Its therapeutic utility depends on its tissue-specific action: it acts as an **antagonist** in the breast but as a partial **agonist** in the endometrium and bone. 1. **Why Option C is Correct:** In breast tissue, Tamoxifen competitively binds to estrogen receptors (ER), blocking the proliferative effects of endogenous estrogen. Since approximately 70% of breast cancers are hormone-dependent, Tamoxifen is the gold standard for the treatment and prophylaxis of **ER-positive breast carcinoma** in both pre- and post-menopausal women. 2. **Why Other Options are Incorrect:** * **Carcinoma of the Prostate (A):** This is an androgen-dependent malignancy. Treatment typically involves androgen deprivation therapy (e.g., GnRH agonists like Leuprolide or anti-androgens like Flutamide), not anti-estrogens. * **Carcinoma of the Ovary (B):** While some ovarian cancers express ER, Tamoxifen is not a primary treatment modality. Standard care involves platinum-based chemotherapy (e.g., Carboplatin and Paclitaxel). * **Seminoma (D):** This is a germ cell tumor of the testis. It is highly radiosensitive and chemosensitive (e.g., BEP regimen: Bleomycin, Etoposide, Cisplatin), but not responsive to SERMs. **High-Yield NEET-PG Pearls:** * **Side Effects:** Increased risk of **endometrial carcinoma** (due to agonist action on the uterus) and **thromboembolism** (DVT/PE). * **Beneficial Side Effect:** It prevents post-menopausal bone loss (agonist action on bone). * **Drug Interaction:** It is a prodrug activated by **CYP2D6**. Potent inhibitors like Fluoxetine or Paroxetine can decrease its efficacy. * **Alternative:** For post-menopausal women, **Aromatase Inhibitors** (e.g., Letrozole, Anastrozole) are often preferred over Tamoxifen.

Q: Which phase of the cell cycle is resistant to most chemotherapeutic agents that are classified as phase-specific?

G0. ### Explanation **Correct Option: A (G0 Phase)** The **G0 phase (Resting Phase)** is the period where cells are quiescent and have exited the replicative cycle. Most cell cycle-specific (CCS) chemotherapeutic agents target metabolic processes active during DNA synthesis or cell division. Since cells in G0 are not actively dividing, they lack the targets (like topoisomerase, thymidylate synthase, or mitotic spindles) that these drugs attack. This makes G0 the most resistant phase and a major cause of tumor recurrence, as these "dormant" cells can re-enter the cycle after treatment ends. **Incorrect Options:** * **B (G1 Phase):** This is the pre-synthetic phase. While less sensitive than S or M, certain drugs like **Vinblastine** or **Asparaginase** can act here. * **C (G2 Phase):** This is the post-synthetic phase where proteins for mitosis are synthesized. It is specifically targeted by **Bleomycin** and **Etoposide**. * **D (M Phase):** The Mitotic phase is the most sensitive phase for **Vinca alkaloids** (inhibit microtubule assembly) and **Taxanes** (inhibit microtubule disassembly). **NEET-PG High-Yield Pearls:** 1. **Cell Cycle Specific (CCS) Drugs:** Act on dividing cells (e.g., Antimetabolites, Vincas, Taxanes). They are **schedule-dependent** (best given in divided doses or infusions). 2. **Cell Cycle Non-Specific (CCNS) Drugs:** Act on both resting and dividing cells (e.g., Alkylating agents like Cyclophosphamide, Cisplatin). They are **dose-dependent** (bolus doses). 3. **S-Phase Specific:** Most Antimetabolites (Methotrexate, 5-FU, Cytarabine). 4. **Growth Fraction:** Tumors with a high growth fraction (more cells in cycle, fewer in G0) respond better to chemotherapy (e.g., Burkitt’s Lymphoma).

Question 1

A 42-year-old female with acute lymphoblastic leukemia is being treated with a multi-drug chemotherapy protocol. On day 3 of treatment, she develops confusion, seizures, and laboratory investigations show: serum uric acid 12 mg/dL, potassium 6.2 mEq/L, phosphate 7.8 mg/dL, calcium 6.5 mg/dL, and creatinine 2.8 mg/dL. She was given allopurinol prophylaxis before starting chemotherapy. Which agent would have been more effective in preventing this complication?

Accepted Answer

Rasburicase administered before chemotherapy initiation

Answer

Febuxostat at higher doses

Answer

Probenecid with increased hydration

Answer

Sodium bicarbonate for urinary alkalinization

Question 2

A pharmaceutical company develops a new checkpoint inhibitor targeting LAG-3 (Lymphocyte Activation Gene-3) for melanoma. Compared to PD-1 inhibitors, what advantage would combination therapy with both agents theoretically provide?

Accepted Answer

Dual blockade of different inhibitory pathways enhancing T-cell activation

Answer

Complete elimination of immune-related adverse events

Answer

Activation of humoral immunity instead of cellular immunity

Answer

Reduced cost of treatment due to synergistic dosing

Question 3

Which drug is used exclusively in organ transplantation and autoimmune diseases, but not in cancers?

Accepted Answer

Cyclosporine

Answer

Cyclophosphamide

Answer

Methotrexate

Answer

6-Mercaptopurine

Question 4

Tamoxifen is useful in which of the following conditions?

Accepted Answer

Estrogen receptor-positive breast carcinoma

Answer

Carcinoma of the prostate

Answer

Carcinoma of the ovary

Answer

Seminoma

Question 5

Which phase of the cell cycle is resistant to most chemotherapeutic agents that are classified as phase-specific?

Accepted Answer

G0

Answer

G1

Answer

G2

Answer

M

Anticancer Drugs — MCQs

Anticancer Drugs — MCQs

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