Tumor-parenchyma interface and long-term oncologic outcomes after robotic tumor enucleation for sporadic renal cell carcinoma

Abstract

Objective: Tumor enucleation has been shown to be oncologically safe for elective treatment of renal cell carcinoma (RCC); yet, evidence on long-term oncologic outcomes after robotic tumor enucleation is lacking. In this study we provide a detailed histopathological analysis of tumor-parenchyma interface and the long-term oncologic outcomes after robotic tumor enucleation for sporadic RCC in a high-volume referral center.

Materials and methods: We selected consecutive patients undergoing robotic tumor enucleation for sporadic RCC by experienced surgeons with at least 4 years of follow-up. Pattern of pseudocapsule (PC) invasion, thickness of healthy renal margin removed with the tumor, margin status and recurrence rate were the main study endpoints. Multivariable models evaluated independent predictors of PC invasion.

Results: Overall, 140 patients were eligible for the study. Of these, 127 (91%) had complete data available for analysis. Median thickness of healthy renal margin was 0.57 mm (interquartile range [IQR] 0.24-103). A distinct peritumoral PC was present in 121/127 (95%) tumors with a median thickness of 0.28 mm (IQR 0.14-0.45). In 24/121 (19.8%) cases, RCC showed complete PC invasion. At multivariable analysis, increasing tumor diameter, endophytic rate > 50% and papillary histology were significantly associated with complete PC invasion. Positive surgical margins were reported in 3/127 (2.4%) cases. At a median follow-up of 61 months (range 48-76), one patient died due to metastatic RCC. Among patients alive at follow-up, no cases of recurrence at the enucleation site were recorded, while three cases (2.4%) of renal recurrence (elsewhere in the ipsilateral kidney) and three cases (2.4%) of systemic recurrence were found.

Conclusions: Distinct RCC-related features were associated with complete PC invasion. By providing a microscopic layer of healthy renal margin in almost all cases, robotic tumor enucleation achieved negative surgical margins in the vast majority of patients, even in case of complete PC invasion. At long-term follow-up, no recurrences were found at the enucleation site. Although our findings need to be confirmed by larger studies with longer follow-up, robotic tumor enucleation appears oncologically safe in experienced hands for the treatment of sporadic RCC.

Keywords: Enucleation; Partial nephrectomy; Pseudocapsule; Recurrence; Renal Cell Carcinoma; Robotics.