Impact of duration of induction therapy on survival in newly diagnosed multiple myeloma patients undergoing upfront autologous stem cell transplantation.

The optimal duration of induction therapy (IT) in transplant-eligible multiple myeloma (MM) patients in not well defined, resulting in a wide variation in clinical practice. The objective of our study was to determine whether the duration of IT in patients undergoing upfront autologous stem cell transplantation (ASCT) has an impact on progression-free survival (PFS) in the era of proteasome inhibitors and immunomodulatory drugs. A total of 596 patients who underwent ASCT at Mayo Clinic between 2007 and 2014 were included. The patients were divided into two cohorts based on the duration of IT: IT ≤ 4 and IT > 4 months. At a median follow-up of 54·5 months from ASCT, the median PFS in the IT ≤ 4 group was 28 months [95% confidence interval (CI), 25-33], compared to 26 months in the IT > 4 group (95% CI, 24-31) [P = 0·605]. There was no significant difference in overall survival (OS) in the two groups (P = 0·904). The lack of impact of IT duration on PFS and OS was consistent in subgroups with high-risk features at diagnosis (International Staging System III or high-risk cytogenetics) and different depths of pre-transplant response [≥very good partial response (VGPR) and <VGPR]. In conclusion, prolonging the duration of IT beyond 4 months does not impact survival in patients with newly diagnosed MM who complete a single line of IT followed by consolidation with ASCT.