Evaluation of PFS ratio in patients with cancer enrolled in early-phase clinical trials: A single center, retrospective analysis.

Abstract

e14025 Background: Progression-free survival ratio (PFSr) has been proposed as a direct evaluation of treatment benefit in advanced cancer patients, based on the hypothesis that the natural history of cancer is accelerating and therefore successive lines of treatments become less efficient over time. Consequently, PFS at line +2 (PFS2) is expected to be shorter than PFS at line +1 (PFS1), whereas a PFS2/PFS1 ratio > 1.3 might reflect treatment benefit. However, this hypothesis has been poorly documented, especially in the context of early phase trials where determining treatment benefit is becoming key. We therefore proposed to evaluate PFSr in a large cohort of cancer patients enrolled in early phase clinical trials at Gustave Roussy Drug Development Department. Methods: Patients enrolled in at least two phase 1 studies for advanced solid tumors or lymphomas were retrospectively identified. Demographical, clinical and therapeutic data were collected. Time to progression (PFS) was measured from treatment initiation to progression, using radiological evaluations. Patients who had gone off-trial for reasons other than progression were censored. PFSr was defined as the ratio of the PFS under line 2 divided by the PFS under line 1 and might be censored in presence of censored PFS2. Ratio distribution in this population was estimated using Kaplan Meier. Calibration of the ratio was proposed for hypothesis testing. The influence of therapeutic class and combination versus monotherapy was studied via non parametric Gehan-Wilcoxon tests or Mick tests. Results: 212 patients enrolled between 2009 and 2016 in at least two phase 1 clinical trials were included, corresponding to 113 different clinical trials. PFSr distribution was described and correlated with demographical, clinical and therapeutic data. The relevance of the usual 1.3 PFSr cut-off to determine treatment benefit was evaluated. Final analysis results will be presented at the time of the congress. Conclusions: This study, one of the first to establish PFSr in a large cohort of patients treated in early phase clinical trials, provides guidelines for using PFSr to assess the impact of treatment sequences in advanced cancer patients.