Presentation Authors: Hiroshi Kikuchi*, Takashige Abe, Ryuji Matsumoto, Jun Furumido, Haruka Miyata, Takahiro Osawa, Sachiyo Murai, Nobuo Shinohara, Sapporo, Japan
Introduction: Previously, several researchers reported that a high RENAL nephrometry score (RNS) was associated with an unfavorable pathology in renal cell carcinoma (RCC) patients. Our group also reported that RNS was associated with the annual tumor growth rate on linear regression analysis of 47 renal tumors with at least a 12-month follow-up duration (Matsumoto et al., IJU 2014). These observations suggest that anatomic features of RCCs are associated with the tumor proliferative ability or malignant potential. In the present study, in order to gain further insights into the association between the anatomy of small clear cell renal cell carcinoma (ccRCC) and tumor proliferative activities, we evaluated the association between RNS and tumor proliferative activity assessed by immunohistochemistry.
Methods: The current study included 145 pathological T1 (pT1) ccRCCs. Tumor proliferative activity was assessed with the Ki67 index and microvessel density (MVD). RNS was retrospectively assessed in the present study. We divided patients into three groups according to RNS (RNS: 4-6: low-complexity, 7-9: moderate complexity, and 10-12: high-complexity tumors) and compared the Ki67 index as well as MVD among the three groups. The association between the Ki67 index/MVD and each component (R, E, N, A, L, h) was also evaluated.
Results: These included 56 low-complexity, 84 moderate-complexity, and 5 high-complexity tumors. The median Ki67 index of all tumors was 5.34% (interquartile range: 3.28-8.57). The median Ki67 indexes of low, moderate, and high-complexity tumors were 3.97, 6.39, and 11.27%, respectively, with a significant difference among the three groups (Kruskal-Wallis test, p=0.0004). On the other hand, the median MVDs of low, moderate and high-complexity tumors were 14.11, 14.42, and 21.22%, and there were no significant differences among the three groups. In terms of each RNS component, there were significant differences in the Ki67 index among the three groups in N (p=0.0101) and L (p=0.0280) components, respectively.
Conclusions: The association between RNS and the Ki67 index in pT1 ccRCC further supports the previous findings that the anatomy of RCC is associated with the malignant potential of localized ccRCC, which may provide additional information to aid with treatment decisions.