Outcomes of partial nephrectomy for non-metastatic cT2 renal tumors: Results from a Canadian multi-institutional collaborative.

690 Background: The role of partial nephrectomy (PN) is not well defined for cT2 renal cell carcinoma (RCC) as compared to radical nephrectomy (RN). The aim of this study was to examine oncological outcomes of PN as compared to RN for non-metastatic cT2 RCC. Methods: The Canadian Kidney Cancer information system was used to define patients who underwent surgery for non-metastatic cT2 RCC from January 2011 to October 2022. Patients with clear-cell, papillary, and chromophobe RCC were included. Other histology, multiple tumours, and hereditary RCC syndrome patients were excluded. Each PN patient was individually matched to RN up to 1:4 depending on availability of patients based on tumor size (+/- 1cm), histology, grade (clear cell and papillary), and necrosis (clear cell). Matched patients were analyzed as clusters. Results: A total of 1523 patients were identified, and 50 PN patients met study criteria who were then matched to 185 RN patients. Both groups had similar age, gender, smoking status, BMI, Charlson comorbidity index score, symptoms at presentation, baseline eGFR, hemoglobin and pathological characteristics. PN patients had smaller tumors (7.6 cm [IQR 2] vs 8.4 [IQR 2.4], p=0.05), had higher likelihood of undergoing open surgery (72.9% vs 31.8%, p<0.0001) and less likely received adrenalectomy (2% vs 24.3%, p=0.0004). Positive surgical margin rates were similar in both groups (8.2% in PN vs 3.4% in RN, p=0.2). Median follow up was not significantly different in either group (3.6 yrs [IQR 4.7] in PN vs 3.3 [4.7] yrs in RN, p=0.9). During the follow up period, PN patients had higher risk of local recurrence (HR 3.0, 95%CI 1.08-8.37), lower risk of distant metastasis (HR 0.36, 95%CI 0.15-0.88), better cancer specific survival (HR 0.56, 95%CI 0.18-1.78) and overall survival (HR 0.36, 95%CI 0.11-1.19) and as compared to RN. At 6 months and beyond after surgery, PN patients had less decline in eGFR than RN patients (-16.6 [SD 21.1] vs -24.4[SD 16.2], p=0.0002). Complications rates between PN and RN were (18% vs 9%, p=0.057). Conclusions: In this multi-institutional Canadian cohort of patients with non-metastatic cT2 RCC undergoing surgery, PN compared to RN was associated with slightly higher risk of peri-operative complications, better preservation of renal function, and higher risk of local recurrence. The lower risk of distant metastasis and death was likely from residual confounding unaccounted for in the individual patient match. [Table: see text]