Length of treatment after partial or complete remission in immunotherapy for metastatic melanoma: An EUMelaReg real world study.

9531 Background: A significant proportion of patients (pts) with non-resectable melanoma treated with immune checkpoint inhibitors (ICI) achieve durable remissions, but there is limited data on the optimal duration of ICI therapy in these pts. Therefore, the influence of the duration and maintenance of ICI therapy in pts with a partial (PR) or complete remission (CR) on further outcome was investigated. Methods: Primary objectives was the survival outcome after achieving PR or CR in non-resectable stage III/IV melanoma in relation to baseline prognostic variables and duration of maintenance treatment with ICIs in 1 st line. This retrospective study evaluated melanoma cases from the EUMelaReg treatment registry, who achieved a best overall response (BOR) of PR or CR with either single agent anti-PD1 or combined anti-PD1/anti-CTLA4 in 1 st line. Cases were stratified according to treatment duration after achieving a PR or CR: 12 M. To address immortal time bias, cases with early progression were cloned into all respectively compatible strata. These synthetical strata were further analyzed and compared by propensity score weighting, and robust confidence intervals were retrieved by bootstrapping techniques. Results: A total of 1,291 pts were included in the analysis. After cloning, 2,144 cases could be stratified to the synthetical arms of 12 M (42.1%) treatment continuation after achieving PR or CR. Adjusted Kaplan-Meier estimates showed that treatment until progressive disease (PD) or > 12 M after remission resulted in prolonged progression-free (PFS) and overall survival (OS) compared to the 12 M or until progression after achieving PR or CR compared to pts treated for < 6 M. Table: see text