AB88. Natural history of renal cell carcinoma: an immunohistochemical analysis of growth rate in patients with delayed treatment

OBJECTIVES: To investigate the natural history of renal cell carcinoma (RCC) with delayed treatment, and immunohistochemically analyzed the correlation between some biomarkers and the growth rate of RCC. PATIENTS AND METHODS: We reviewed our institutional databases to identify renal tumors which were confirmed RCC by delayed surgical treatment after at least 12 months of active surveillance (AS). Growth rate was defined as average growth rate of the maximal diameter on CT or MRI. The clinicopathological characteristics, and immunohistochemical biomarkers (Ki-67, p53, bcl-2, and VEGF) were analyzed the correlation with the growth rate of RCC. RESULTS: We identified 45 RCCs from 45 patients. The mean patient age was 54 years (range, 26-78 years). The mean tumors size increased from 2.39 cm (range, 0.10-6.70 cm) at presentation to 4.54 cm (range, 1.40-11.80 cm) after a mean 45.4 months (range, 12-155 months) of AS. The mean growth rate was 0.71 cm/year (range, 0.07-4.44 cm/year), 36 (80.0%) tumors presented a growth rate ≤1.00 cm/year. Clear cell RCC (ccRCC) had a trend of growing faster than other histological subtypes. Pathological grade was significantly correlated with the growth rate of ccRCC (P=0.043). The Ki-67 labeling index (R=0.359, P=0.016) and p53 expression (P=0.019) were significantly correlated to the growth rate of RCC. CONCLUSIONS: In general, RCCs under AS have a slow growing with a wide variation of growth rate, a portion of RCCs present rapid growth kinetics. Histological type, grade, Ki-67 and p53 are the potential predictors of growth rate of RCC during AS.