Role of flow cytometric measurable residual disease assessment in multiple myeloma

Abstract

Despite the high rates of complete response achieved with current treatments, patients with multiple myeloma (MM) continue to relapse due to the presence of minute amounts of residual MM cells. These are referred to as "minimal" or "measurable" residual disease (MRD).As conventional serological and morphological techniques have become suboptimal for evaluating the depth of response, high sensitivity methods, next-generation flow (NGF) cytometry and next-generation sequencing are recommended in MRD assessment in the bone marrow. Under optimal conditions, these methods can detect one MM cell among 1,000,000 normal cells (a sensitivity of 10 -6 ). Furthermore, imaging techniques, particularly positron emission tomography-computed tomography, have an important role to play in MRD assessment outside of the bone marrow, and alternative blood-based methods for MRD assessment are under investigation. There is a growing consensus that MRD is the most relevant prognostic factor in MM, and achieving a negative MRD status significantly prolongs progression-free survival and overall survival. This review examines the various methods used to detect MRD, including methodological aspects of NGF. It also presents considerations for implementing MRD as a surrogate biomarker to accelerate drug development and guide MM therapy.