Progression-free survival as a predictor of overall survival in metastatic renal cell carcinoma treated with contemporary targeted therapy.

BACKGROUND: The majority of metastatic renal cell carcinoma (mRCC) clinical trials that examined targeted agents used progression-free survival (PFS) as the primary endpoint. Whether PFS can be used as a predictor of overall survival (OS) is unknown.
METHODS: Patients from 12 cancer centers who received targeted therapy for mRCC were identified. Landmark analyses for progression at 3 months and 6 months after drug initiation were performed to minimize lead-time bias. A proportional hazards model was used to assess the utility of PFS for predicting OS.
RESULTS: In total, 1158 patients were included. The median follow-up was 30.6 months, the median age was 60 years, and the median Karnofsky performance status was 80%. For the entire cohort, the median PFS was 7.6 months, and the median OS was 19.7 months. In the landmark analysis, the median OS for patients who progressed at 3 months was 7.8 months compared with 23.6 months for patients who did not progress (log-rank test; P < .0001). Similarly, for patients who progressed at 6 months, the median OS was 8.6 months compared with 26 months for patients who did not progress (P < .0001). Compared with those who did not progress, for the patients who progressed at 3 months and at 6 months, the hazard ratios for death adjusted for adverse prognostic factors were 3.05 (95% confidence interval, 2.42-3.84) and 2.96 (95% confidence interval, 2.39-3.67), respectively. Similar results were demonstrated with landmark analyses at 9 months and at 12 months and in the bootstrap validation. Kendall tau rank correlation and a Fleischer model demonstrated a statistically significant dependent correlation.
CONCLUSIONS: PFS at 3 months and at 6 months predicted OS, and the current results indicated that PFS may be a meaningful intermediate endpoint for OS in patients with mRCC who receive treatment with novel agents.