Beyond Clear Cell: Rethinking Postoperative Surveillance for Non-clear Cell Renal Cell Carcinoma Subtypes.

BACKGROUND AND OBJECTIVE: Current risk stratification for non-clear cell renal cell carcinoma (nccRCC) is largely derived from clear cell RCC (ccRCC) data. We evaluated recurrence patterns following surgery for nccRCC and compared the prognostic performances of various international guidelines. METHODS: We retrospectively analyzed patients with surgically managed nonmetastatic nccRCC (2003-2015). Patients were stratified by American Urological Association (AUA), European Association of Urology (EAU), and National Comprehensive Cancer Network (NCCN) risk groups. Model performance was assessed via C-index, integrated Brier score (IBS), and calibration plots. Optimal surveillance duration was defined as the time required to capture 95% of recurrences and the time until the 10-yr conditional recurrence risk fell below 5%, accounting for non-RCC deaths as a competing risk. KEY FINDINGS AND LIMITATIONS: Papillary RCC (pRCC) was the most common subtype (420/712, 59%). Median follow-up was 11.6 yr (IQR: 133-148 mo). Recurrences occurred in 116 patients, most frequently in the abdomen (44/116, 38%). The 5-yr recurrence-free survival (RFS) was 86% (95% confidence interval [CI]: 83-89). Chromophobe RCC (chRCC) had the lowest stage-adjusted subdistribution hazard of recurrence (sHR) (sHR: 0.21, 95% CI: 0.12-0.40). AUA risk-stratification schema provided higher discrimination and lower prediction error (C-index 0.69, IBS 0.104) compared with that of EAU (C-index 0.67, IBS 0.118) and NCCN (C-index 0.66, IBS 0.115). Late recurrences (>5 yr) were common, comprising 27% of all observed recurrences. As a single-center, retrospective study, these findings may not be broadly generalizable. Surveillance duration metrics should be interpreted with caution. CONCLUSIONS AND CLINICAL IMPLICATIONS: Outcomes in this predominantly pRCC and chRCC cohort challenge the current nccRCC surveillance guidelines: abdominal recurrences were the most common, supporting continued cross-sectional imaging. Late recurrences (>5 yr) argue against stopping surveillance at 5 yr and highlight the need for improved risk-adapted surveillance schedules. PATIENT SUMMARY: Current national guidelines for postsurgery follow-up for kidney cancer are based on its most common type. However, their appropriateness for less common forms remains unknown. This study shows that the less common form, non-clear cell renal cell carcinoma, primarily comes back after surgery in the abdomen and can often come back more than 5 yr postoperatively. Therefore, doctors should monitor these patients for a longer duration and focus on abdominal imaging to enable earlier detection. Advancing practice.