Rates of adjacent organ invasion in non-metastatic renal cell carcinoma: a population-based study

Abstract Introduction Pathological T4 (pT4) renal cell carcinoma (RCC) is defined by adjacent organ invasion. The rate of pT4 and its associated clinicopathological characteristics received little attention in non-metastatic (M0) RCC. Methods Within the Surveillance, Epidemiology, and End Results (SEER) database (2004–2022), we identified M0 RCC nephrectomy patients and assessed pT4 rates. Results Of 129,075 M0 RCC nephrectomy patients, 733 (0.6%) harbored pT4 stage. Annual pT4 rates decreased from 1.4% in 2004 to 0.4% in 2022 (p<0.001). According to tumor size, the pT4 rate was 0.1% in tumors <7 cm and increased from 0.7% in 7–7.9 cm tumors to 6.4% in ≥15 cm tumors (p<0.001). In patients undergoing radical nephrectomy for tumors ≥7 cm, pT4 rate was 2.5% (578/22,981). According to histology, pT4 rates were 2.3% (376/16,703) in clear-cell RCC, 3.0% (81/2,682) in papillary RCC, 1.2% (27/2,274) in chromophobe RCC, 6.7% (75/1,119) in sarcomatoid dedifferentiated tumors, 13.2% (7/53) in collecting duct carcinomas, and 8.0% (12/150) in other variant histologies (p<0.001). Compared to pT2–3 patients, pT4 patients more frequently underwent lymphadenectomy (63.3% [366/578] vs. 30.0% [6,724/22,403], p<0.001). Among patients who underwent lymphadenectomy, lymph node invasion was more common in pT4 than in pT2–3 stage (83.6% [298/366] vs. 54.8% [3,901/6,724], p<0.001). Conclusion In M0 RCC, pT4 is rare. It is virtually non-existent in tumors <7 cm. The highest pT4 rates are observed in variant histologies. Compared to pT2–3, pT4 is associated with higher lymphadenectomy use and lymph node invasion rates. Collectively, these findings provide descriptive population-level benchmarks.