Meta-analyses on progression-free survival as a surrogate endpoint for overall survival in triple-negative breast cancer

Purpose: Earlier studies suggest progression-free survival (PFS) may be used as a surrogate endpoint for overall survival (OS) in metastatic breast cancer, which could shorten follow-up duration and speed up assessment of treatment effects. However, to our knowledge, the association between them is still unclear in advanced or metastatic triple-negative breast cancer (TNBC). Methods: A literature-based meta-analysis followed by correlation analysis was conducted in advanced or metastatic TNBC. Weighted multiple regression analysis was then used to test the strength of the association between medians of PFS and OS, and the association between HR_PFS and HR_OS. Results: Fourteen randomized clinical trials published between January 2007 and August 2019, 31 median pairs for PFS and OS, and 17 pairs for HR_PFS and HR_OS from 3,880 patients were selected. The Pearson correlation coefficient between medians of PFS and OS was 0.84 (95% confidence interval (CI) 0.68–0.92, p < 0.001), and the correlation coefficient between HR_PFS and HR_OS was 0.86 (95% CI 0.63–0.95, p < 0.001). Weighted multiple regression analysis showed HR_PFS was the most significant predictor of HR_OS among covariates analyzed (p < 0.001). Both the medians of PFS and OS correlation, and the HR_PFS and HR_OS correlation were 0.79 (p < 0.001), 0.80 (p = 0.001), respectively, in the 11 trials excluding immunotherapy and bevacizumab-based therapy trials. Conclusions: Our analysis suggests PFS can be strongly correlated with OS and considered a valid surrogate endpoint for OS in advanced or metastatic TNBC.