Abstract
BACKGROUND: Response remains an important endpoint in clinical cancer trials. However, the prognostic utility of best tumor response in metastatic renal cell carcinoma (mRCC) remains vague. OBJECTIVE: To define the prognostic relevance of the depth of remission in mRCC. DESIGN, SETTING, AND PARTICIPANTS: Pooled data from the Pfizer database for 2749 patients from phase 2 and 3 clinical trials in mRCC were analyzed. Tumor shrinkage was categorized according to the best percentage change in the sum of the largest diameter of target lesions. Outcome was computed using Kaplan-Meier curves and correlation was assessed via Cox regression, including a 6-mo landmark. INTERVENTION: Sunitinib, sorafenib, axitinib, temsirolimus, or temsirolimus and interferon-α. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Categorized tumor shrinkage, overall survival (OS), progression free survival (PFS). RESULTS AND LIMITATIONS: Major tumor shrinkage of 60% or more occurred in approximately 10% of patients and was associated with median OS of 54.5 mo. OS expectations steadily decreased with depth of remission (26.4, 16.6, 10.4, and 7.3 mo). The association was maintained when stratified by type of therapy, line of therapy, and performance status. Cox proportional regression analyses for the 6-mo landmark confirmed the prognostic relevance of major tumor shrinkage (hazard ratio 0.29, 95% confidence interval 0.22-0.39; p<0.001). The major limitation of our study is the variability of imaging intervals among studies. CONCLUSIONS: This is the first and largest analysis of best tumor response in mRCC. We demonstrate that depth of remission is an independent prognostic factor in mRCC. PATIENT SUMMARY: It remains unknown whether tumor shrinkage during therapy is needed to achieve clinical activity in metastatic renal cell carcinoma. Our analysis shows that the magnitude of tumor shrinkage correlates with better survival in patients. This observation may be used as a clinical research tool in future trials. TRIAL REGISTRATION: NCT00054886, NCT00077974, NCT00267748, NCT00338884, NCT00137423, NCT00083889, NCT00065468, NCT00678392.