Role of Composite Measurable Residual Disease Assessment with PET-CT and flow cytometry in Multiple Myeloma patients undergoing Autologous Transplant.

Background: Bone marrow (BM) Measurable Residual Disease (MRD) assessments underestimate disease burden in multiple myeloma, as focal lesions can exist outside the marrow. Functional imaging, like positron emission tomography-computed tomography (PET-CT), offers valuable insights into residual disease beyond the marrow. Combining marrow flow cytometry (FCM) with PET-CT for a composite MRD (cMRD) assessment before and after autologous stem cell transplant (ASCT) is expected to provide prognostic information, particularly in settings where patients receive extended duration of anti-myeloma therapy prior to ASCT. Methods: In this retrospective cohort study, we evaluated the prognostic impact of cMRD in newly diagnosed multiple myeloma (NDMM) patients who underwent triplet/quadruplet-based induction followed by ASCT from January 2017 to June 2023. cMRD was assessed before ASCT and again around day 100 post-transplant. cMRD negativity was defined as undetectable residual clonal plasma cells (sensitivity 1×10 Results: Among 106 patients undergoing ASCT, 82 had cMRD assessments before and on day 100 post-ASCT. Median pre-ASCT treatment duration was 11 months (interquartile range [IQR]: 4-18). At the pre-ASCT time point, sixty seven percent patients were bone marrow MRD negative (BM-MRD Conclusions: Pre-ASCT cMRD assessment using both PET-CT and bone marrow FCM provides prognostic value in NDMM. This approach is particularly relevant in real-world settings where patients often receive prolonged induction therapy before ASCT.