Among vinca alkaloids, which is more likely to cause severe bone marrow suppression?

• A. Vincristine has greater myelosuppression
• B. Vinblastine has greater myelosuppression
• C. Both cause no myelosuppression
• D. Neither cause myelosuppression

Answer: (B)

Toxicity patterns differ within the vinca alkaloids. Bone marrow suppression is the dose-limiting toxicity for several chemotherapies, and among these agents it is most prominent with vinblastine. Vincristine, while it inhibits mitosis, is delivered with relatively less impact on hematopoietic cells and is mainly limited by neurotoxicity. Vinblastine, on the other hand, markedly affects rapidly dividing bone marrow progenitors, leading to significant neutropenia and other marrow suppression. So, vinblastine is the one more likely to cause severe bone marrow suppression. (Vinorelbine also causes marrow suppression but generally not as severely as vinblastine.)