Response Evaluation Criteria in Solid Tumors 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?

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BackgroundWe evaluated whether best overall response changes by designating primary renal lesions as either target or nontarget lesions and assessing response per Response Evaluation Criteria in Solid Tumors in mRCC patients 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 MethodsPatients with mRCC with an intact primary tumor and at least 1 extrarenal measurable lesion were included in this study. 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. ResultsThere were 41 patients included. Median ΔSOD of the primary lesion and metastatic target lesion were −6.0% (range, −34.0% to 17.6%), and −18.0% (range, −100.0% to 120.0%), respectively. For metastasis-only target lesions, the best overall response of 2 patients (4.9%) changed from stable disease to partial response. When we categorized patients into responders and nonresponders, response determination using metastasis-only target lesions resulted in significantly better discrimination of time to progression (14.9 vs. 4.3 months, P = .001) and overall survival (18.5 vs. 9.6 months, P = .036) between 2 groups. Using all target lesions, both TTP (14.9 vs. 5.4 months, P = .056) and OS (18.0 vs. 10.6 months, P = .155) were not statistically significant. ConclusionWhen treating nonnephrectomized mRCC patients, selecting metastasis-only lesions as target lesions might be better to determine response, which might be more representative of survival end point.