Pb2120 the impact of depth of response before and after autologous stem cell transplant for multiple myeloma patients

Background: Over the last decade there has been an improvement on the outcome of multiple myeloma (MM) patients. In patients eligible for high‐dose chemotherapy and autologous stem cell transplant (ASCT), the inclusion of bortezomib in induction chemotherapy (ICT) has significantly delayed disease progression. Several studies have shown that achieving a complete response (CR) after ASCT is a predictive factor for disease control, leading to improved progression‐free survival (PFS) and overall survival (OS). Aims: Assessing the impact of depth of response before and after ASCT on PFS in a population of MM patients treated with ICT including bortezomib and identifying predictive/protective factors for disease progression. Methods Retrospective study of MM patients admitted for ASCT between January 2015 and December 2017 treated in first line with VCd (bortezomib, cyclophosphamide, and dexamethasone) or VTd (bortezomib, thalidomide and dexamethasone). Demographic (gender, age), clinical and biological variables at diagnosis were collected, as well as response obtained before and at D + 100 after ASCT, and time elapsed between ASCT and disease progression. Statistical analysis was performed using STATA software (V13). Results: A total of 53 MM patients in the first line setting were included in this study. 43.4% were male; median age at diagnosis was 60 years old (IQR, 40‐72). Both groups (VCd and VTd) had similar baseline characteristics. Median follow‐up after induction chemotherapy was 20.6 months. PFS of patients who achieved CR or very good partial response (VGPR) post‐induction was 73.7%, versus 60% in patients who achieved partial response (PR) or lower (log‐rank p = 0.07). Looking at different variables that could modify the time between ASCT and disease progression, we observed that ISS stage 3 is an independent predictive factor for disease progression (HR 3.1; p = 0.014), and obtaining CR/VGPR at D + 100 post‐ASCT is an independent protective factor against disease progression (HR 0.2; p = 0.004). Summary/Conclusion: Despite the relatively short follow‐up period, in this population of transplant‐eligible MM patients, we have demonstrated that the depth of response after induction chemotherapy (VGPR/CR) is critical for a greater PFS, and that a profound reduction in tumor burden (VGPR/CR) after ASCT allows for prolonged disease control. However, ISS stage 3 is a risk factor for disease progression regardless of the obtained response.