Long-Term Molecular Results Of The Gimema VEL-03-096 Trial: Molecular Remission Achievement and Loss Are Major Outcome Predictors

Background and aims The extensive use of new drugs in multiple myeloma (MM) allowed the achievement of unprecedented levels of cytoreduction and major advantages in survival rates, though almost all patients still relapse after a successful treatment. PCR-based minimal residual disease (MRD) studies are powerful prognostic tools, able to indentify patients at high risk of relapse. Thus, there is a growing interest in MRD to modulate therapy also in MM, as already happens in other lymphoid neoplasms. However available reports have a too short follow-up to be conclusive. In particular some points need to be addressed: 1) which is the long-term outcome of patients achieving molecular remission (MR) in the absence of further treatment? 2) What is the prognostic impact of MR loss? 3) How long is the window between MR loss and clinical relapse? These issues have been addressed based on the mature results of the GIMEMA VEL-03-096 trial [EudraCT Number 2004-000531-28], which currently has a median follow-up (mFU) of 93 months. Patients and methods Inclusion criteria and treatment schedule have been already reported [Ladetto et al., J Clin Oncol 2010]. MRD was assessed on bone marrow at diagnosis, study entry, after two VTD courses, at the end of treatment and then every six months up to clinical relapse. Patients underwent MRD detection using both qualitative nested PCR and Real Time Quantitative (RQ)-PCR, employing immunoglobulin heavy chain-derived patient specific primers, as described [Voena et al., Leukemia 1997; Ladetto et al., Biol Bone Marrow Transpl 2000; van der Velden et al., Leukemia 2007]. MR was defined as negative MRD results by nested-PCR or less than 1EE-04 by RQ-PCR. Loss of MR was defined as an increase of MRD levels of at least one log in consecutive samples at whenever timepoint. For survival analysis duration of response (DOR), progression-free survival (PFS), time to next treatment (TNT) and overall survival (OS) rates were used, as detailed in IMWG criteria [Rajkumar et al., Blood 2011]. Results Thirty-nine patients were enrolled. So far 27 serological progressions, 22 clinical relapses needing salvage treatment and 12 deaths (two non-MM-related) were observed. Median PFS was 60 months, median TNT 67 months and OS at mFU was 64%. 270 of the planned samples for MRD monitoring (86%) were actually received by the centralized lab. Currently, 26 MR and 11 MR losses have been registered. The achievement of MR was strongly associated with a better outcome, in terms of median DOR (62 vs 9 months, p<0.001), PFS (67 vs 22 months, p<0.001), TNT (108 vs 30 months, p<0.001) and resulted significant for OS, too (72% vs 48% at mFU, p=0.04, Figure 1A-B). Moreover, patients with ongoing MR, MR loss or not achieving MR at all showed increasing risk of relapse, respectively (DOR not reached vs 38 vs 9 months, PFS 92 vs 63 vs 22 months, TNT not reached vs 72 vs 30 months, each p<0.001, Figure 2). Interestingly, the time lag between MR loss and clinical relapse for patients achieving and then loosing MR was comparable to that between end of consolidation and clinical relapse for patients never obtaining MR (TNT 19 vs 11 months p=0.34). Finally, analyzing the relationship between MR achievement, MR loss and need for a salvage treatment, of the 26 patients who obtained MR only 11 (42%) received a retreatment at a median time of 42 months (range: 22-87 months). Of these 11 clinical relapses, 7 were anticipated by a molecular relapse (64%), occurring at a median time of 9 months (range: 2-39 months). The 4 relapses not anticipated by MR loss occurred in cases with inadequate follow-up sampling or at least two years after the end of the planned molecular follow-up. Conclusions Besides confirming the strong prognostic value of PCR-based MRD monitoring in MM, our long-term results indicate the following: 1) the 42 months TNT of patients achieving MR underlines the excellent disease control of MM patients once obtained MR; 2) the occurrence of MR loss heralds relapse, with a TNT from MR loss comparable to TNT of patients not achieving MR; 3) there is a 9 months lag between MR loss and need for salvage treatment. These observations will have increasing relevance considering that ongoing methodological developments will allow effective MRD monitoring in the vast majority of MM patients. Disclosures: Off Label Use: Bortezomib and thalidomide as post-transplant consolidation during first-line treatment of multiple myeloma. Ladetto:Celgene: Research Funding, Speakers Bureau; Jannsen Cilag: Research Funding, Speakers Bureau; Mundipharma: Research Funding, Speakers Bureau; Roche: Research Funding, Speakers Bureau; Amgen: Research Funding, Speakers Bureau. Cavallo:Celgene: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Jannsen Cilag: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding. Caravita:Celgene: Honoraria, Research Funding; Jannsen Cilag: Honoraria. Guglielmelli:Celgene: Research Funding. Boccadoro:Celgene: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Jannsen Cilag: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding. Palumbo:Bristol-Myers Squibb: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Janssen Pharmaceuticals: Consultancy, Honoraria; Millenium: Consultancy, Honoraria; Onyx: Consultancy, Honoraria; Amgen: Consultancy, Honoraria.