Progression and hyperprogression after anti-PD1 therapy for unresectable stage III or IV melanoma patients

e21021 Background: Primary progression (PP) and secondary progression (SP) to anti-PD1 therapy (APD) are poorly described in advanced melanoma in real life practice. Hyperprogression with a deleterious effect is reported in many cancers but is poorly assessed in advanced melanoma. Methods: Characteristics of 793 patients treated by APD (nivolumab or pembrolizumab) between July 2014 and May 2018 were collected from MelBase, a prospective French biobank (NCT02828202).We considered: group A (progressive disease as best response), group AHP (hyperprogression) within group A patients (progression/death within 3 months with normal initial LDH and ECOG at baseline, and either ECOG increased from 0 to 3-4, either LDH increased from normal to elevated or both), group B SP (response or stable disease then progression). Characteristics for all and survival for patients alive at progression (AAP) were also described. Results: Median follow-up was 11.3 months (Q1-Q3 4.8–23.6). Characteristics at baseline are in the table. In group A, 14% patients died at progression; within 262 patients AAP, 17% continue APD (the same or switch), 15.1% (CI95 11.1-20.6) were alive 1-year after progression (1YAP); 20.5% for patients in first line and 11.5% for pretreated. In group AHP, 41% patients died at progression; within 48 patients AAP, 12% continue APD, 11.1% (CI95 7.8-13.6) were alive 1YAP. In group B, 11% patients died at progression; within 88 patients AAP, 36% continue APD, 10.3% (CI95 5.2-20.1) were alive 1YAP, 15.9% for patients in first line and 7.0% for pre-treated. Conclusions: Our study shows that PP and SP to APD differ at baseline, but have similar survival rates at progression, while mechanisms involved might be different, providing important landmarks to build second line trials. This study thus highlights the existence of hyperprogressors among which 41% patients died within 3 months, as well as describes their associated characteristics. [Table: see text]