Minimally Invasive Assessment of Peripheral Residual Disease During Maintenance or Observation in Transplant-Eligible Patients With Multiple Myeloma.

JCO In multiple myeloma (MM), measurable residual disease (MRD) is assessed in bone marrow (BM). However, less invasive evaluation of peripheral residual disease (PRD) in blood could be advantageous and less cumbersome. We investigated the prognostic value of PRD monitoring after 24 cycles of maintenance in 138 transplant-eligible patients with MM enrolled in the GEM2012MENOS65/GEM2014MAIN clinical trials. PRD was assessed using next-generation flow (NGF) and mass spectrometry (MS). Positive PRD by NGF in 16/138 (11.5%) patients was associated with a 13-fold increased risk of progression and/or death; median progression-free survival (PFS) and overall survival (OS) were 2.5 and 47 months, respectively. Considering patients' MRD status in BM as the reference, PRD detection using NGF showed positive and negative predictive values of 100% and 73%, respectively. Presence of PRD helped identifying patients at risk of imminent progression among those with positive MRD in BM. Patients with undetectable PRD according to both NGF and MS showed 2-year PFS and OS rates of 97% and 100%, respectively. In multivariate analyses including the Revised International Staging System and the complete remission status, only MRD in BM and PRD by NGF showed independent prognostic value for PFS. This study supports the use of less invasive PRD monitoring during maintenance or observation in transplant-eligible patients with MM.