Primary renal cell carcinoma: relationship between 18F-FDG uptake and response to neoadjuvant sorafenib

OBJECTIVEThe objective of this study was to collect preliminary data on the predictive value of pretherapy F-fluorodeoxyglucose positron emission tomography in primary renal cell carcinoma (RCC) patients undergoing neoadjuvant therapy with sorafenib. METHODSAs part of a clinical trial to assess the safety and feasibility of using neoadjuvant sorafenib in patients with RCC, 26 patients [19 with clear cell RCC (ccRCC), seven with non-clear cell RCC (non-ccRCC)] underwent F-fluorodeoxyglucose positron emission tomography with concurrent computed tomography (CT) before commencing sorafenib therapy and 17 (13 ccRCC, four non-ccRCC) of them also at the end of sorafenib therapy. The maximal standard uptake value at baseline (SUVbase) and its change from baseline after therapy (SUVdiff and SUVrel) were recorded and correlated with therapy response, measured as percentage size change on CT, using Spearman’s rank and Pearson’s correlation coefficients. RESULTSSUVbase and size change on CT showed a strong inverse correlation (Spearman’s rank correlation coefficient=−0.72, P=0.0003; Pearson’s correlation coefficient=−0.64, P=0.002) in ccRCC. There was no statistically significant correlation in non-ccRCC (Spearman’s rank correlation coefficient=0.67, P=0.098; Pearson’s correlation coefficient=0.46, P=0.32). In neither group was there a statistically significant correlation between change in SUV and size after commencement of treatment. All findings were limited by the small number of samples included in this analysis. CONCLUSIONPrimary ccRCC tumors with lower SUVbase are more likely to respond to neoadjuvant sorafenib, whereas this trend was not observed for non-ccRCC tumors.