Objectives: Previous studies revealed an unclear correlation between the growth rate of renal cell carcinoma (RCC) and tumor grade and did not focus on certain histological subtype. This report investigated the correlation between the growth rate and tumor grade in clear cell RCC (ccRCC).
Methods: We reviewed 60 patients with 61 ccRCC confirmed by delayed surgeries after at least 12 months of active surveillance. The linear growth rate (LGR), volumetric growth rate (VGR), and volume doubling time (VDT) were calculated, and their correlations with clinicopathologic characteristics were analyzed.
Results: The mean LGR, VGR, and VDT were 0.86 (range 0-4.74) cm/year, 20.96 (range 0.31-211.93) cm(3)/year, and 667 (range 33-3321) days, respectively. ccRCCs with high grade had greater LGR (P < 0.001) and VGR (P = 0.001) and lower VDT (P = 0.017) than ccRCCs with low grade. Grade (OR = 5.185, P = 0.004) was the only independent risk factor of LGR >0.5 cm/year, and grade (OR = 3.006, P = 0.046) and initial size (OR = 0.392, P = 0.004) were independent risk factors of VDT <1 year. Five patients developed metastasis after surgery with LGR >0.5 cm/yr altogether; of them, four had cancer-related death by the last follow-up.
Conclusions: Fast growth rate of ccRCC is significantly correlated with high tumor grade and may result in poor prognosis, especially for those with LGR >0.5 cm/yr.