Correct Answer: C. Oprelvekin (IL-11)
Oprelvekin (IL-11) is a thrombopoietic agent specifically indicated for chemotherapy-induced thrombocytopenia (CIT). It acts as a megakaryocyte growth and development factor, directly stimulating platelet production from bone marrow precursors. In Indian cancer centres, oprelvekin is the gold-standard cytokine for managing severe thrombocytopenia (platelet count <20,000/μL) when transfusion-dependent bleeding occurs post-chemotherapy. The drug works by binding to IL-11 receptors on megakaryocytes, promoting their proliferation and maturation, thereby increasing circulating platelet counts within 5–9 days of initiation. Unlike other supportive agents, oprelvekin directly addresses the platelet deficit rather than preventing further damage or stimulating other cell lines. It is particularly valuable in patients requiring continued chemotherapy cycles, as it allows dose escalation or timely cycle completion without transfusion dependency—a critical outcome measure in Indian oncology practice where blood product availability and transfusion-related complications are significant concerns.
Why the other options are wrong
A. Amifostine — Amifostine is a cytoprotective agent (free-radical scavenger) that reduces chemotherapy toxicity to normal tissues, not a platelet-stimulating drug. It prevents thrombocytopenia rather than treating established low platelet counts. While it may reduce the incidence of CIT in some regimens, it does not increase platelet production once counts have already fallen—making it unsuitable for a patient with already-reduced platelets requiring immediate intervention. B. Filgrastim — Filgrastim is a granulocyte colony-stimulating factor (G-CSF) that stimulates neutrophil production, not platelet production. It is the DOC for chemotherapy-induced neutropenia, not thrombocytopenia. Confusing G-CSF with thrombopoietic agents is a common NBE trap; students may select this thinking 'any growth factor will help,' but filgrastim has no direct effect on megakaryocytes or platelet counts. D. Erythropoietin — Erythropoietin (EPO) is a hematopoietic agent that stimulates red blood cell production, addressing chemotherapy-induced anemia, not thrombocytopenia. While EPO is used in cancer patients with concurrent anemia, it does not increase platelet counts. The question specifically asks for treatment of reduced platelets, making EPO irrelevant despite being a legitimate supportive care drug in oncology.
High-Yield Facts
- Oprelvekin (IL-11) is the only FDA-approved thrombopoietic cytokine for chemotherapy-induced thrombocytopenia with platelet counts <20,000/μL.
- Filgrastim = G-CSF (neutrophils); Oprelvekin = IL-11 (platelets); Erythropoietin = RBCs—each targets a different cell line.
- Oprelvekin onset: 5–9 days; peak effect at 14–19 days post-injection; requires subcutaneous administration.
- Amifostine is a cytoprotective agent (prevents toxicity), not a hematopoietic agent (treats deficiency).
- In Indian oncology, oprelvekin reduces transfusion dependency and allows continuation of chemotherapy cycles without dose delays.
Mnemonics
HGF Trio in Oncology G-CSF → Neutrophils (Filgrastim); IL-11 → Platelets (Oprelvekin); EPO → RBCs (Erythropoietin). Each cytokine targets one cell line—match the deficiency to the growth factor. Cytoprotection vs. Hematopoiesis Amifostine = Protect (prevent damage); Oprelvekin/G-CSF/EPO = Produce (stimulate cells). If the question says 'already low counts,' use a growth factor, not a protectant.
NBE Trap
NBE pairs chemotherapy toxicity with multiple supportive agents (amifostine, filgrastim, EPO, oprelvekin) to test whether students can distinguish cytoprotection (amifostine) from hematopoiesis (growth factors) and identify the correct growth factor for the specific cell line deficit (platelets → IL-11, not G-CSF or EPO).
Clinical Pearl
In Indian tertiary cancer centres, oprelvekin is reserved for severe, transfusion-dependent thrombocytopenia because platelet transfusions carry high alloimmunization risk in multiply-transfused patients. Oprelvekin allows chemotherapy continuation without transfusion dependency—a critical outcome in resource-limited settings where blood product availability is constrained.
_Reference: KD Tripathi Pharmacology Ch. 48 (Hematopoietic Agents); Harrison Ch. 97 (Supportive Care in Cancer)_