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

OBJECTIVE: The objective of this study was to collect preliminary data on the predictive value of pretherapy 18F-fluorodeoxyglucose positron emission tomography in primary renal cell carcinoma (RCC) patients undergoing neoadjuvant therapy with sorafenib.
METHODS: As 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 18F-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 (SUV base) and its change from baseline after therapy (SUV diff and SUV rel) were recorded and correlated with therapy response, measured as percentage size change on CT, using Spearman's rank and Pearson's correlation coefficients.
RESULTS: SUV base 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.
CONCLUSION: Primary ccRCC tumors with lower SUV base are more likely to respond to neoadjuvant sorafenib, whereas this trend was not observed for non-ccRCC tumors.