Organ-specific and tumor-size-dependent responses to sunitinib in clear cell renal cell carcinoma

BACKGROUND: Tyrosine kinase inhibitors (TKIs) have been used as standard therapy for patients with advanced renal cell carcinoma (RCC). However, information on factors predicting response to treatment with TKIs is lacking. This study aimed to assess the association between initial tumor size, involved organs, pre-treatment C-reactive protein (CRP) levels, and reduction in tumor size in patients with clear cell RCC (CCRCC) treated with sunitinib. METHODS: Patients with advanced CCRCC with target lesions with a maximum diameter ≥ 10 mm treated with sunitinib were evaluated. The tumor diameter representing the best overall response was designated as the post-treatment tumor diameter. RESULTS: A total of 179 lesions in 38 patients were analyzed. Organ-specific analysis demonstrated that pre-treatment diameter of lung metastatic lesions had a moderate inverse association with percent reduction in post-treatment tumor diameter (R = 0.341). Lung lesions showed significantly greater percent reductions in diameter than liver and kidney lesions (P = 0.007 and 0.002, respectively). Furthermore, based on a CRP cut-off level of 2.0 mg/dl, mean tumor size reduction was significantly greater in patients with low CRP levels than in patients with high CRP levels in lesions with diameters < 20 mm (P = 0.002). CRP level had no effect on mean size reduction in lesions with a diameter ≥ 20 mm. CONCLUSIONS: Patients with CCRCC with smaller lung metastatic lesions and lower CRP levels may achieve greater percent reductions in tumor size with sunitinib therapy than patients with extra-pulmonary lesions, large lung lesions, and/or higher CRP levels.