Growth and renal function dynamics of renal oncocytomas on active surveillance.

Neves, Joana B; Varley, Rebecca; Agnesi, Stefano; Withington, John; Rodrigues, Filipe B; Warren, Hannah; Yuminaga, Yuigi; Capitanio, Umberto; Rode, Nicola; Grant, Lee; Tran-Dang, My-Anh; El-Sheikh, Soha; Walkden, Miles; Cullen, David; Aitchison, Michael; Patki, Prasad; Mumtaz, Faiz; Barod, Ravi; Bex, Axel; Tran, Maxine G B

OBJECTIVES To study the natural history of renal oncocytomas and address indications for intervention by determining how growth associates with renal function over time, the reasons for surgery and ablation, and disease-specific survival. PATIENTS AND METHODS Retrospective cohort of consecutive patients with renal oncocytoma on active surveillance reviewed at the Specialist Centre for Kidney Cancer at Royal Free London NHS Foundation Trust (2012 to 2019). Comparison between groups was tested using the Mann-Whitney U and the Chi-square tests. A mixed-effects model with a random intercept for patient was used to study the longitudinal association between tumour size and estimated glomerular filtration rate (eGFR). RESULTS Longitudinal data from 98 patients with 101 lesions was analysed. Most patients were male (68.3%), median age was 69 years (IQR 13). The median follow-up was 29 months (IQR 26). Most lesions were small renal masses, 24% measured over 4 cm. Over half (64.4%) grew at a median rate of 2 mm per year (IQR 4). No association was observed between tumour size and eGFR over time (p=0.871). Nine lesions (8.9%) were subsequently treated. Two deaths were reported, neither were related to the diagnosis of renal oncocytoma. CONCLUSION Natural history data from the largest active surveillance cohort of renal oncocytomas to date show that renal function does not seem to be negatively impacted by growing oncocytomas, and confirms clinical outcomes are excellent after a median follow up of over 2 years. Active surveillance should be considered the gold standard management of renal oncocytomas up to 7cm.