Anti-PD-(L)1 can provide overall survival (OS) benefits over conventional treatments for patients with many different cancer types. However, the long-term outcome of cancer patients responding to these therapies remains unknown. This study is an exploratory study that aimed to describe the long-term survival of patients responding to anti-PD-(L)1 monotherapy across multiple cancer types. Data from patients treated with an anti-PD-(L)1 monotherapy in a phase I trial at Gustave Roussy were retrospectively analyzed over a period of 5 years. All cancer types ( = 19) were included. Clinical and biological factors associated with response, long-term survival, and secondary refractory disease were studied.

Among 262 eligible patients, the overall objective response rate was 29%. The median progression-free survival of responder patients (RP) at 3 months was 30 months, and the median OS of RP was not reached after a median follow-up of 34 months. In RPs, 3- and 5-year OS percentages were 84% and 64%, respectively. No death occurred in the 21 complete responders (CR) during the overall follow-up. However, many partial responders (PR) showed subsequent tumor relapses to treatment. Long responders (response ≥2 years) represented 11.8% of the overall population. These findings should be validated in further prospective studies.

There are currently no differences in therapeutic strategies between CRs and PRs to anti-PD-(L)1. We found a striking difference in OS between these two types of responses. Our results are in favor of evaluating patient stratification strategies and intensification of treatments when tumor lesions of a partial responder to immunotherapy stop improving..