Retrospective study of advanced melanoma patients treated with ipilimumab after nivolumab: Analysis of 60 Japanese patients.

Background: Due to resistance and immune-related adverse events (irAE) some melanoma patients require ipilimumab after nivolumab therapy. However, little is known about the result of this switching.

Objective: Investigate the outcome of ipilimumab switching in Japanese patients.

Methods: We retrospectively collected 60 patients who were treated with ipilimumab after nivolumab from 9 institutes in Japan. Information of the primary tumor, treatment, response, irAE), and survival was collected.

Results: In our cohort, acral lentiginous and mucosal melanoma accounted for 53% of the cases. The most common reason for initiating ipilimumab was disease progression (93%). Median interval from the last nivolumab administration to first ipilimumab administration was 29days. Only 38% of patients completed 4 injections of ipilimumab. The best overall response was 3.6%. IrAE occurred in 78% of patients and 70% of those were of grade 3/4 (G3/4) and 31% of patients experienced 2 or more irAEs. An within interval of 28days or less between the last nivolumab administration and ipilimumab administration was correlated with the development of G3/4 pyrexia and 3 or more irAEs, but irAE occurrence did not affect survival. Multivariate analysis showed that endocrine irAE (relative risk=0.22, P=0.015) and skin irAE (relative risk=2.78, P=0.048) were significant factors associated with survival.

Conclusion: In our study, the response ratio to ipilimumab after nivolumab was unsatisfactory and associated with a high frequency of severe irAEs. As there are few second-line treatment options for patients with BRAF wild-type advanced melanoma after nivolumab failure, patients should be closely monitored if ipilimumab is initiated.