Association Between RECIST Changes and Survival in Patients with Metastatic Castration-resistant Prostate Cancer Receiving Docetaxel

We explored the association between Response Evaluation Criteria in Solid Tumors (RECIST) 1.0 and 1.1 changes and overall survival (OS) in patients with metastatic castration-resistant prostate cancer (mCRPC) from the control arms of the VENICE and MAINSAIL phase 3 trials, respectively, receiving docetaxel, prednisone, and placebo. We used Cox proportional hazards regression to evaluate the OS prognostic ability of RECIST changes after adjusting for prognostic factors. In the VENICE trial, the OS hazard ratio (HR) was 0.64 (95% confidence interval [CI] 0.42-0.99; p=0.045) for patients with a partial response (PR) compared to those without PR, and 1.78 (95% CI 1.07-2.95; p=0.026) for those with progressive disease (PD) compared to those without PD. After adjusting for prostate-specific antigen (PSA) changes, PD remained significant (HR 1.85, 95% CI 1.10-3.12; p=0.020). Data from the MAINSAIL trial corroborated the association of PR (HR 0.51, 95% CI 0.22-1.18; p=0.12) and PD (HR 3.51, 95% CI 1.92-6.43; p<0.001) with OS. After adjusting for PSA changes, PD was associated with poor OS (HR 2.36, 95% CI 1.11-5.04; p=0.026). Given the association between RECIST changes and OS, more frequent detection of measurable disease with current imaging techniques, and the poor reliability of bone scan and PSA changes, assessment of RECIST changes on treatment with novel agents in patients with measurable tumors may provide an objective signal of efficacy. PATIENT SUMMARY: In this study, we found an association between changes in objectively measurable tumors according to Response Evaluation Criteria in Solid Tumors (RECIST) and survival in patients with metastatic prostate cancer receiving docetaxel chemotherapy. Since bone scan and prostate-specific antigen changes are unreliable and measurable tumors are more frequently detected now because of better radiographic technology, a focus on RECIST changes should be considered during drug development to provide an objective signal of efficacy.