Absence of Contribution to a Differential Outcome of the Stringent Complete Response IMWG Category Respect to the Conventional CR in Multiple Myeloma. a Validation Analysis Based on the Pethema/GEM2012MENOS65 Phase III Clinical Trial

Introduction: To discriminate different outcomes among patients in CR, the International Myeloma Working Group (IMWG )introduced more stringent CR (sCR) criteria by adding to the pre-existing CR parameters the requirement of a normal free-light chain ratio (sFLCr) plus the absence of clonal plasma cells (PCs) in bone marrow (BM) by immunohistochemistry (IHC). In 2011,the low-sensitivity cytometrycriteria were included as alternative methodology to IHC to define sCR. Aim: To validate the preliminary data of our previous study (Blood 2015. 126:858-62) regarding the lack of influence of an abnormal sFLCr in the outcome of MM patients, through the analysis of a more extensiveseries of newly diagnosed multiple myeloma (NDMM) patients in CR or sCR. Patients and Methods: This study is based on 459 NDMM patients who were transplant candidates and enrolled in the GEM2012MENOS65phase 3trial;evaluable patients were enrolled in a subsequent maintenance trial (NCT02406144).CR and sCR was defined according to the IMWG criteria. Agreeing to the protocol, patients with