e22001 Background: Optimal duration of anti-PD-1 antibody therapy remains undefined. Currently, treatment is given up to two years in metastatic melanoma based on clinical trials. However, recent observations suggest that anti-PD-1 antibodies may work as well if given for shorter time periods. To better understand duration of anti-PD-1 antibody treatment, we reviewed outcomes for patients who discontinued immunotherapy earlier than 2 years in our Cancer Center. Methods: This is a retrospective, single-institution review of metastatic melanoma patients who received anti-PD-1 antibodies from January 2010 to December 2019. We further identified the patients discontinuing treatment before completion of 2 years for reasons other than disease progression. Duration was categorized into three groups: < 6 months (A), 6-12 months (B) and > 12 months (C) and outcomes were analyzed. Progression free survival (PFS) was defined as the time from the initiation of anti-PD1-therapy to the date of progression as determined by treating physician based on radiological, biochemical and/or clinical criteria. Results: 25 patients with mean age 69 years (49-91; N = 19 > 60yo) were identified. Number of patients who received anti-PD-1 antibodies were N = 8, N = 9 and N = 8 in in groups A, B and C respectively. 44% of patients discontinued treatment after achieving either partial or near complete remission, whereas the remaining 66% of patients discontinued treatment due to adverse events. Majority of patients who stopped treatment due to adverse events were older than 60 (71.4%). In 29 months of median follow up (range 11-54), none of patients who received treatment in group B progressed, whereas in groups A and C, 25% percentage progressed in each group with 80% PFS at 12.8 months and 88% PFS at 26 months respectively. 12.5% of patients in group A had progression at 12 months follow up, where no progression was noticed in groups B and C during the same time period. Conclusions: Retrospective analysis of our experience supports other retrospective findings that treatment with anti-PD-1 antibodies more than 12 months might not add further benefit in responding or non-progressing older patients though further study with longer follow up is required.
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