Progression-free survival in advanced ovarian cancer: a Canadian review and expert panel perspective

Ovarian cancer is leading cause of gynecologic cancer mortality in Canada. To date, overall survival (os) has been the most-used endpoint in oncology trials because of its relevance and objectivity. However, as a result of various factors, including the pattern of sequential salvage therapies, measurement of os and collection of os data are becoming particularly challenging. Phase ii and iii trials have therefore adopted progression-free survival (pfs) as a more convenient surrogate endpoint; however, the clinical significance of pfs remains unclear. This position paper presents discussion topics and findings from a pan-Canadian meeting of experts that set out to 1. evaluate the relevance of pfs as a valid endpoint in ovarian cancer; 2. reach a Canadian consensus on the relevance of pfs in ovarian cancer; and 3. try to address how pfs translates into clinical benefit in ovarian cancer. Overall, the findings and the group consensus posit that future studies should 1. ensure that trials are designed to evaluate pfs, os, and other clinically relevant endpoints such as disease-related symptoms or quality of life; 2. incorporate interim futility analyses intended to stop accrual early when the experimental regimen is not active; 3. stop trials early to declare superiority only when compelling evidence suggests that a new treatment provides benefit for a pre-specified, clinically relevant endpoint such as os or symptom relief; and 4. discourage early release of secondary endpoint results when such a release might increase the frequency of crossover to the experimental intervention.