Abstract
Progression-free survival (PFS) has been used as a surrogate endpoint for overall survival (OS) in lung cancer trials. The pattern of response to immune-checkpoint inhibitors (ICIs) differs from that to conventional chemotherapy, so immune-related response evaluation criteria were proposed. This study aims at determining which PFS measure, PFS assessed per immune-related response evaluation criteria (iPFS), or conventional criteria (cPFS), is the better surrogate endpoint for OS in trials of ICIs in lung cancer. We selected clinical trials in lung cancer that administered ICIs to at least one arm and reported both median OS and median PFS from PubMed, Embase, and The Cochrane Library. We compared the correlation between treatment effect (hazard ratio) on OS and cPFS or iPFS and the correlation between median OS and median cPFS or iPFS using weighted linear regression at trial level. We analyzed 78 ICI arms (13,438 patients) from 54 studies, including 66 arms with cPFS, seven arms with iPFS, and five arms with both kinds of PFS. We demonstrated an excellent correlation between treatment effect (hazard ratio) on OS and iPFS (R(WLS)(2) = 0.91), while the correlation was moderate for cPFS (R(WLS)(2) = 0.38). Similarly, the correlation between median OS and median iPFS was also strong (R(WLS)(2) ranging from 0.86 to 0.96) across different phases of trials and different types of lung cancer, ICI, and treatment modalities, while it was much weaker for median cPFS (R(WLS)(2) ranging from 0.28 to 0.88). In conclusion, iPFS provides better trial-level surrogacy for OS than cPFS in trials of ICIs in lung cancer.