Use of early primary tumor response to predict overall survival in patients with metastatic RCC undergoing treatment with sunitinib.

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329 Background: In metastatic renal cell carcinoma (mRCC) patients treated with sunitinib and the primary tumor in situ, there is minimal predictive data available to help guide clinicians during treatment with targeted therapy. In prior studies, early primary tumor response (PTR) was associated with improved overall PTR, but the effect on overall survival (OS) is unknown. The purpose of our study was to evaluate whether early PTR was associated with improved OS in mRCC patients undergoing treatment with sunitinib. Methods: We reviewed our institutional database to identify patients with mRCC treated with sunitinib with primary tumor in situ. Clinical and pathological data were collected for each patient. Sequential abdominal CT or MRI scans were reviewed to evaluate PTR. Early PTR was defined as ≥ 10% decrease in tumor diameter within the first 90 days of treatment. Univariable and multivariable stepwise Cox proportional hazards regression analysis were performed to identify predictors of OS in these patients. Results: 75 consecutive patients were identified between 2005 and 2009 with a median follow-up of 15 months. 24 patients exhibited an early PTR; median maximum response 23.1% (range: −53.4, −10.2) and decrease in primary tumor diameter at a median of 90.5 days. Early PTR was associated with a decreased risk of death on multivariate analysis (HR: 0.18; 95% CI 0.05, 0.62, p<0.01). In addition, median OS was improved in patients with an early PTR (30.2 vs. 12.7 months). Independent predictors of decreased survival on multivariate analysis included local symptoms, multiple bone metastases, clinical evidence of venous thrombus, LDH > upper limit of normal, and >2 visceral metastatic sites. Conclusions: Early PTR ≥ 10% is associated with improved survival, better response in metastatic sites, and better overall PTR in patients with mRCC. Future studies should consider this variable when evaluating sunitinib in mRCC treatment. [Table: see text]