Metastatic potential of a renal mass according to original tumour size at presentation

OBJECTIVE To determine the metastatic potential of renal masses based on original tumour size. MATERIALS AND METHODS We identified 2651 patients who had undergone surgical resection for a unilateral, sporadic renal tumour between 1990 and 2006. Associations of tumour size with synchronous metastasis at presentation [M1 renal cell carcinoma (RCC)] and development of metastases, death from RCC, and death from any cause after surgery were evaluated using logistic and Cox proportional hazards regression. RESULTS Of the 2651 patients studied, 182 (6.9%) presented with M1 RCC. Tumour size was significantly greater in patients with M1 RCC than in patients with M0 RCC (a median size of 10 vs 4.5 cm; P < 0.001). Only 1 of the 629 patients (0.2%) with a tumour < 3 cm had M1 RCC and that tumour was 2.5 cm. The risk of M1 RCC increased from 1.1% for patients with tumours 3-3.9 cm to 16.5% for patients with tumours >= 7 cm. Of the 2124 patients with M0 RCC, 430 developed distant metastases at a median (range) of 1.4 (0.1-16.2) years after surgery. Only 9 of the 498 patients (1.8%) with a tumour < 3 cm developed distant metastases after surgery. Each 1-cm increase in tumour size increased the risk of death from RCC by 20% [hazard ratio (HR) 1.20; 95% confidence interval (CI) 1.18-1.22; P < 0.001] and death from any cause by 10% (HR 1.10; 95% CI 1.09-1.12; P < 0.001). For the 1346 patients who were still alive at last follow-up, the median (range) duration of follow-up was 6.9 (0.1-19.7) years. CONCLUSIONS Tumour size is significantly associated with metastases in patients with renal masses. Patients with tumours < 3 cm have a low risk of synchronous metastatic disease.