Is Progression-Free Survival a Good Indicator of Overall Survival for Pazopanib in Patients With Synovial Sarcoma?

OBJECTIVES: Synovial sarcoma (SS) is a malignant soft tissue sarcoma with a poor prognosis because of a high rate of metastasis and/or recurrence. Progression-free survival (PFS) is a surrogate endpoint widely used for overall survival (OS) in oncology, but limited data is available for SS. We aimed to review all relevant studies evaluating the validity of PFS as a surrogate for OS in SS.

METHODS: Published articles were examined to identify the PFS or OS from January 1, 2012, to December 31, 2020, with the keywords of pazopanib AND soft AND tissue AND sarcoma. Four observational studies, which reported both PFS and OS, were used for synthesizing the relationship between PFS and OS. A total of 60 adult patients with advanced synovial sarcoma were included and the median sample size was 16. The linear regression was performed to evaluate the outcome surrogacy.

RESULTS: There was a weak correlation between median PFS and median OS (Pearson correlation coefficients=0.327, 95% confidence interval: -0.925 to 0.980, p=0.673). The slope of the regression line for the association between median PFS and median OS was 0.44 (p=0.697), and the determination coefficient of the linear regression analysis was 0.092, which means that median PFS accounted for median OS by 9% (determination coefficient=0.092).

CONCLUSIONS: PFS does not seem to be strongly related to OS for pazopanib on advanced SS. Although the study is limited by the small sample size, it adds important histology-specific information to the existing literature on the treatment of advanced SS.