Early reduction in primary tumor (PT) size independently predicts better overall survival in patients with metastatic renal cell carcinoma (mRCC) treated with sunitinib, researchers reported.

Jason Abel, MD, and colleagues at the University of Texas M.D. Anderson Cancer Center in Houston, studied 75 patients with mRCC who had no prior systemic treatment and who received sunitinib with their PT in situ. Subjects had a median follow-up 15 months. The median initial diameter of the PT was 9.7 cm. Median PT size decreased by a maximum of 10.2% overall and by 36.4% in patients who had early minor PT response, defined as a 10% or greater decrease within 60 days of treatment initiation.

The study, led by Christopher G. Wood, MD, Professor of Urology and Deputy Chairman of the Department of Urology, showed that the median overall survival for patients without minor PT response, with minor PT response after 60 days, and with early minor PT response was 10.3, 16.5, and 30.2 months, respectively, according to a report in European Urology (published online ahead of print). After adjusting for multiple variables, early minor response was independently associated with a 74% decreased mortality risk.

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“If these findings are validated,” the investigators noted, “early PT response may be used to identify patients with improved survival to help guide future therapy.”

The researchers pointed out that the study was limited by a relatively small patient sample size, the study’s retrospective nature, and the significant number of patients with unclassified histologic subtypes of RCC. “In addition, patients who responded to therapy were more likely to continue on therapy, which could contribute to differences in survival.”