Significance of cycle 1 bone marrow biopsy in predicting outcomes and toxicities of venetoclax-based therapy for myeloid malignancies.

For older unfit patients receiving venetoclax-based induction, data on the significance of interim bone marrow biopies (BMBx) findings on clinical outcomes is lacking. We retrospectively evaluated interim BMBx results performed on Cycle 1 days 21-28 of venetoclax-based therapy in 69 adults with myeloid malignancies to determine whether blast clearance was associated with overall survival (OS) and overall response rate (ORR). Median age was 75 years (range 69-78). Results demonstrated blast reduction (BR, <5% blasts) in 71%. Venetoclax was held to allow count recovery in 86% of these patients. Achieving interim BMBx BR was significantly associated with OS (p = 0.0033) and ORR (Cohen's kappa 0.39). Patients whose venetoclax was held experienced low rates of infection and reduced cytopenias. These findings support the importance of cycle 1 BMBx assessment during venetoclax-based therapies, specifically in predicting which patients will achieve optimal outcomes and in mitigating toxicity.