When to stop immunotherapy for advanced melanoma: the emulated target trials.

BACKGROUND

Immune checkpoint inhibitors (ICIs) have demonstrated their efficacy with a 7.5-year overall survival (OS) close to 50% for advanced stages. The design of clinical trials provides for treatment until progression or toxicity, or for a maximum duration of two years. Prolonged follow-up of responders after treatment cessation shows sustained response and a low risk of relapse in the months following cessation. To date, the optimal duration of anti-PD-1 therapy for metastatic melanoma remains unestablished. The objective of this work was to evaluate the optimal duration of ICI administration.

METHODS

We emulated target trials using the cloning, weighting and censoring approach. Each emulation trial aimed to compare the effect of discontinuing versus continuing ICIs at a specific timepoint, among patients still under treatment and with disease control at that time. Patients were from MelBase between 2015 and 2021.

FINDINGS

435 participants in the MelBase cohort were eligible and were included in the 6-month discontinuation emulated trial. The results showed significantly lower OS when treatment was discontinued, than when treatment was prolonged for at least three months. The 48-month survival difference was 37.8% (95% confidence interval [CI] 19.8-60.5), and the corresponding restricted mean survival time difference was 8.3 months (95% CI: 4.1-12.7). Neither the 12-month nor the 18-month discontinuation emulated trials showed evidence of benefit of either discontinuing or continuing ICIs at either of these timepoints. The 24-month discontinuation emulated trial results were more in favor of discontinuing than continuing treatment at that time point, with an absolute 48-month survival rate that was 10.5% higher (95% CI 4.4-18.1).

INTERPRETATION

These results suggest that a one-year course of immunotherapy is both necessary and sufficient for patients with advanced melanoma. Prolonged treatment beyond 2 years does not appear to be beneficial in terms of survival and could even be detrimental.

FUNDING

This work was supported by a grant from Bristol Myers Squibb, Merck Sharp Dhome, Pierre Fabre, Novartis, Sun Pharm, Regeneron, Sanofi, Nektar, Therapeutics and Oncyte.