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.