Treatment-Free Survival: A Novel Outcome Measure of the Effects of Immune Checkpoint Inhibition—A Pooled Analysis of Patients With Advanced Melanoma

PURPOSE: Outcome measures that comprehensively capture attributes of immuno-oncology agents, including prolonged treatment-free time and persistent treatment-related adverse events (TRAEs), are needed to complement conventional survival end points. METHODS: We pooled data from the CheckMate 067 and 069 clinical trials of nivolumab and ipilimumab, as monotherapies or in combination, for patients with advanced melanoma. Treatment-free survival (TFS) was defined as the area between Kaplan-Meier curves for two conventional time-to-event end points, each defined from random assignment: time to immune checkpoint inhibitor (ICI) protocol therapy cessation and time to subsequent systemic therapy initiation or death. TFS was partitioned as time with and without toxicity by a third end point, time to cessation of both ICI therapy and toxicity. Toxicity included persistent and late-onset grade 3 or higher TRAEs. The area under each Kaplan-Meier curve was estimated by the 36-month restricted mean time. RESULTS: At 36 months, many of the 1,077 patients who initiated ICI therapy were surviving free of subsequent therapy initiation (47% nivolumab plus ipilimumab, 37% nivolumab, 15% ipilimumab). The restricted mean TFS was longer for nivolumab plus ipilimumab (11.1 months) compared with nivolumab (4.6 months; difference, 6.5 months; 95% CI, 5.0 to 8.0 months) or ipilimumab (8.7 months; difference, 2.4 months; 95% CI, 0.8 to 4.1 months); restricted mean TFS represented 31% (3% with and 28% without toxicity), 13% (1% and 11%), and 24% (less than 1% and 23%) of the 36-month period, respectively, in the three treatment groups. TFS without toxicity was longer for nivolumab plus ipilimumab than nivolumab (difference, 6.0 months) or ipilimumab (difference, 1.7 months). CONCLUSION: The analysis of TFS between ICI cessation and subsequent therapy initiation revealed longer TFS without toxicity for patients with advanced melanoma who received nivolumab plus ipilimumab compared with nivolumab or ipilimumab. Regardless of treatment, a small proportion of the TFS involved grade 3 or higher TRAEs.