7558 Background: Survival in patients with multiple myeloma (MM) continues to improve with the newer therapies, but there is no clear evidence of a cure and patients continue to relapse. However, most patients have the most extended period without progression with their first-line therapy, and subsequent therapies often provide a shorter duration of response due to the use of drugs with overlapping mechanisms of action and, more importantly, a shorter first remission, pointing toward more aggressive disease biology. With newer immunotherapies being used at 1st relapse, this may change. We designed this study to explore the natural history of MM after the 1st relapse and define the predictors of outcome after the initial relapse. Methods: We identified all patients in the Mayo Clinic database diagnosed between Jan 2004-June 2019 who had had initial disease progression. The study cohort included 2005 patients. We explored the overall survival (OS) from the time of documented disease progression or the start of second-line treatment in patients who had not met IMWG criteria before second-line therapy. Front-line therapy was grouped into those with either an IMiD or PI, both IMiD and PI, daratumumab with IMiD and PI, and none of these agents. The IMiD and PI were always used with dexamethasone with or without an alkylator. Results: The median age was 63 (range 24-95) years and 60% were male. The median estimated follow-up from diagnosis for all patients was 86 mos. (95% CI; 82, 88) and the median time to progression from the start of therapy was 25 mos. (95% CI; 24, 26). The median OS from the first progression was 45 mos. (95% CI; 42, 50), 36 mos. for those diagnosed before 2009, and 52-53 mos. for those diagnosed later. On univariate analysis, age <70 at 1st relapse, RISS I, novel agents in initial therapy, CR in the first line, diagnosis after 2009, initial remission >18 mos, and initiation of therapy before IMWG progression were all associated with improved OS after 1st relapse (Table). On multivariate analysis, age <70, RISS I, initial remission >18 mos, and initiation of therapy before IMWG progression were all associated with improved OS after 1st relapse. Conclusions: The study provides an estimate of the outcomes and significant predictors of outcomes after 1st relapse in patients with MM. These factors should be taken into consideration when designing clinical trials in this patient population. In particular, these factors identify a high-risk group of patients not always identified by baseline characteristics and should be the focus of future trials. [Table: see text]
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