Abstract
e19525
Background: Minimal residual disease (MRD) negativity after completed therapy is associated with longer progression-free survival (PFS) in patients with multiple myeloma (MM). Current standard of care for MRD testing use flow cytometry and/or next generation sequencing (NGS)-based assays applied on bone marrow (BM) aspirate samples. To develop a strategy for MRD tracking in peripheral blood (PB), we were motivated to evaluate MALDI-TOF head-to-head with established bone marrow-based MRD assays. Methods: We used MALDI-TOF mass spectrometry to detect M-proteins in PB. Our cohort included patients who had serum samples available at 2 timepoints including during active disease and within 60 days of MRD results as determined by flow cytometry of BM aspirates. The cohort enrolled 71 patients (26 females, 45 males) with a median age of 61 years (37-78 years). Twenty-seven patients had high-risk cytogenetics at baseline. Patients were classified at diagnosis as ISS1 (n = 38), ISS2 (n = 18) or ISS3 (n = 6). The flow cytometry based MRD assay was performed using MSKCCs 10-color, single-tube method. MALDI-TOF analysis was performed as described by Mills et al. Samples taken during active disease were used to identify the mass/charge ratio of the M-protein at baseline and in follow-up samples. MALDI-TOF results were compared to flow cytometry bone marrow-based MRD results. Results: The median time between diagnosis and the MRD timepoint was 13.4 months (3.4-91 months). MALDI-TOF in PB and flow cytometry BM-based MRD results were concordant for 44/71 (62%) patients (8+/+, 36 -/- respectively) while 27 were discordant (10 +/-, 17-/+). Fifty-four of 71 patients were in complete response (CR) (45/54 in sCR) at the time of MRD. MALDI-TOF was still positive in 13 of these 54 CR patients. In this cohort, the median PFS since MRD assessment was not reached in the 2 subgroups of double negative patients (n = 31) or in patients with a positive result in at least one technique (n = 23) with a median follow-up of 11.2 months (0-34.6 months). Conclusions: In 44/71 (62%) samples, MALDI-TOF of PB results and flow cytometry BM-based MRD results were concordant. MALDI-TOF of PB may be useful for detecting measurable residual disease and for the monitoring of MM patients during maintenance therapy with the future goal to rule out early recurrent disease.