Risk of metastasis for T1a renal cell carcinoma

While active surveillance for small renal mass is gaining acceptance, controversy still continues on true metastatic potential of small renal cell carcinoma (RCC). Thus, we investigated the risks of synchronous/metachronous metastases and their potential predictors among T1a RCC patients who underwent surgical treatment. We reviewed data from 2114 patients who received radical or partial nephrectomy for small renal tumor (a parts per thousand currency sign4 cm) from 1990 to 2013. For our study, patients were stratified into four different groups according to tumor size (group 1: 0-1.0 cm, group 2: 1.1-2.0 cm, group 3: 2.1-3.0 cm, group 4: 3.1-4.0 cm). Univariate and multivariate analyses were performed to analyze metastatic potentials according to tumor size and identify useful predictors of metastases. Among 1913 T1a RCC patients, there were low but nonnegligible rates of metastases (group 2: 1.1 %, group 3: 3.3 %, group 4: 6.0 %, respectively). Kaplan-Meier analysis showed significant differences in metastasis-free survivals between groups (p < 0.001). A linear positive association was observed between tumor size and metastatic rate (p < 0.001). Diabetic T1a RCC patients showed significantly inferior metastasis-free survival than nondiabetic counterparts (p = 0.003). Multivariate analysis revealed that tumor size and history of diabetes mellitus were independently associated with metastasis in T1a RCC. As T1a RCCs present low but nonnegligible risk of metastasis, patients with small renal mass should be counseled on such risk when offered active surveillance. Larger tumor size and history of diabetes mellitus may be associated with higher risk of metastasis in T1a RCC.