834P - Recist Response of the Primary Lesion in Metastatic Renal Cell Carcinomas Treated with Sunitinib: Does the Primary Lesion have to be regarded as a Target Lesion?

Abstract

ABSTRACT Background There is no consensus on including the primary lesion as the target lesion when evaluating the response of non-nephrectomized metastatic renal cell carcinoma (mRCC) patients (pts). We evaluated whether best overall response changes by designating primary renal lesions as either target or non-target lesions and assessing response per RECIST in mRCC pts treated with sunitinib. In addition, we evaluated whether discordance, if any, leads to a difference in predictive value of response in terms of time-to-progression (TTP) and overall survival (OS). Patients and methods Among pts with histologically confirmed mRCC treated with sunitinib at Asan Medical Center, pts with an intact primary tumor and at least one extra-renal measurable lesion were included. To measure the influence of including the primary lesion as the target lesion, the variation of the sum of diameters (ΔSOD) of target lesions and best overall response, assessed from all target lesions and from metastasis-only target lesions, was documented separately. For examining differences of two methods in predictive function in estimating TTP and OS, pts were categorized according to their best overall responses as responders [complete response (CR) and partial response (PR)] or non-responders [stable disease (SD) and progressive disease (PD)] for all target lesions and metastasis-only target lesions, respectively, and then analyzed for survival. Results Forty-one pts were included in this study. Median ΔSOD of the primary lesion and metastatic target lesion were -6.0% (range, -34.0–17.6%), and -18.0% (range, -100.0–120.0%), respectively. For metastasis-only target lesions, the best overall response of two pts (4.9%) changed from SD to PR. When we categorized pts into responders and non-responders, response determination using metastasis-only target lesions resulted in significantly better discrimination of TTP (14.9 vs 4.3 months, P = 0.001) and OS (18.5 vs 9.6 months, P = 0.036) between two groups. Using all target lesions, both TTP (14.9 vs 5.4 months, P = 0.056) and OS (18.0 vs 10.6 months, P = 0.155) were not statistically significant. Conclusion When treating non-nephrectomized mRCC pts, selecting metastasis-only lesions as target lesions might be better to determine response, which might be more representative of TTP and OS. Disclosure All authors have declared no conflicts of interest.