The correlation between metastasis-free survival and overall survival in non-metastatic castration resistant prostate cancer patients from the Medical Data Vision claims database in Japan

Background and purpose: Several recent randomized controlled trials (RCTs) in non-metastatic castration resistant prostate cancer (nmCRPC) have demonstrated a significant improvement in metastasis-free survival (MFS); however, an improvement in overall survival (OS) is not reported yet. Since the surrogacy of MFS to OS has not been formally investigated in nmCRPC in Japan, this study evaluated the correlation between MFS and OS among a nmCRPC population in Japan. Methods: This is a retrospective longitudinal observational cohort study in patients with nmCRPC using the Japanese Medical Data Vision (MDV) database covering over 20 million patients. A total of 1236 patients with CRPC who had no prior medical history of cancer except prostate cancer and no distant metastasis, and who fulfilled PCWG2 criteria, were identified. Following the identification of nmCRPC, patients' medical records were investigated for subsequent events of metastasis and death. Results: The median follow-up time was 24 months. Median MFS was 28 months (95% CI: 24.0 to 33.0 months) and median OS could not be estimated (95% CI: not estimated). There was a statistically significant correlation between MFS and OS (Pearson's correlation coefficient = 0.62; 95% CI: 0.58-0.65; p < .0001, Spearman's correlation coefficient = 0.62; 95% CI: 0.58-0.65; p < .0001 and Kendall's tau statistic = 0.53; 95% CI: 0.49-0.56; p < .0001). Conclusions: The results of this study indicate a significant correlation between MFS and OS. It may justify the usefulness of MFS as surrogate for OS in nmCRPC.