Correlation of progression-free survival (PFS) and overall survival (OS) in men with metastatic castration-resistant prostate cancer (CRPC) who failed first-line chemotherapy: Results from the SPARC Trial.

5150 Background: It has been shown in chemotherapy naïve patients that PFS is a statistically significant predictor of OS. The main objectives of this analysis were to explore whether PFS at 3-months is a predictor of OS and to investigate the dependence between PFS and OS in CRPC men who failed first line chemotherapy. METHODS: Data from SPARC, a multi-national, randomized, double-blind trial, comparing satraplatin + prednisone vs placebo + prednisone in 950 CRPC patients were used. For the purpose of this analysis, the two treatment groups were combined. PFS was defined as the time from date of randomization to date of first progression (bone scan progression, radiographic, soft-tissue progression, symptomatic, or skeletal related events) or death, whichever occurred first. PFS at 3-months was defined as a binary variable in the following manner: if a patient experienced any type of progression at or before 3-months then this was considered as an event. If a patient did not progress at 3 months then he was censored. Landmark analysis of PFS at 3-months predicting OS was performed. In addition, the proportional hazards model was used to assess the significance effect of PFS at 3-months in predicting OS adjusting for the stratification factors. Finally, the association between OS and PFS was investigated using a statistic that estimates Kendall's tau measure of association for bivariate time to event outcomes subject to censoring. RESULTS: 477 (56%) men progressed at 3-months of 853 men who were alive at 3-months. The median survival times were 34.5 weeks (95% CI = 30.8-40.4) and 78.7 weeks (95% CI=70.1-83.2, p-value<0.001) respectively in men who did and did not experience progression at 3-months. Men who had progressed at 3-months were more likely to die than men who did not progress (hazard ratio = 2.16, 95% CI =1.84 -2.55, p-value < 0.001). The dependence between PFS and OS was 0.29 (95% confidence limits = 0.24-0.33, p-value < 0.00001). CONCLUSIONS: PFS at 3-months predicts OS. The results of this large retrospective analysis show moderate, but strong statistical dependence between PFS and OS. Future studies are needed to assess the clinical relevance of the distinct components of progression. [Table: see text].

Duke Scholars

Author Susan Halabi Biostatistics & Bioinformatics, Division of Biostatistics