Histopathological upstage, recurrence, and survival in a population-based cohort of surgically treated patients with clinical T1b renal cell carcinoma.

Abstract

731 Background: T1 renal cell carcinoma (RCC) is considered to have a low malignant potential. Partial nephrectomy (PN) is recommended for nephron sparing whenever technically feasible also for T1b RCC. Despite a favorable prognosis there remains a risk for upstaging and recurrence, and the place for PN in clinical T1b tumors is questionable. Therefore, we have characterized these variables and overall survival (OS) in a real-world population-based cohort of patients with clinical T1b RCC. Methods: Patients without metastases registered in the National Swedish Kidney Cancer Register (99% of RCCs diagnosed in Sweden) 2005-2014 with clinical T1b (> 4-7 cm), surgically treated and with a follow-up of ≥ 5 years were included. Results: There were 2137 patients (1300 males, 837 females) with a mean age of 66 years; 82% had clear cell (ccRCC), 11% papillary (pRCC) and 6% chromophobe (chRCC) RCC. Radical nephrectomy (RN) was performed in 1836 patients and PN in 301 patients. After histopathological examination 435 (20%) were upstaged to pathological (p) T3: 21% of ccRCCs, 13% of pRCC and 20% of chRCCs. Recurrent disease after ≥ 5-years follow-up was diagnosed in 127 (29%) pT3 patients and in 238 (14%) with pT1b, 322 (18%) in ccRCC, 127 (11%) in pRCC and 6(5%) in chRCC. Lung metastases occurred in 52% of patients with recurrencies and 144 (39%) of these had two or more metastatic sites. Patients with pT3RCC had a 67% five-year OS compared to 83% in pT1b patients (Log-rank test, p<0.001). Regardless of other factors, patients treated with PN had a higher 5-year OS of 86% compared to 79% in patients treated with RN (Log-rank test, p=0.006). In multivariable analyses, lower age, female sex, smaller tumors, N0, pRCC and chRCC, and pT1b stage were significantly associated with longer survival. A hazard ratio of 0.93 [95% CI 0.65-1.32] for PN indicated that PN was non-inferior to the treatment with RN in patients with clinical T1bRCC. Conclusions: Clinical T1bRCC is a malignant disease with risk for upstaging and tumor recurrence. Nonetheless, the results indicate that PN is non-inferior to the treatment with RN in clinical T1bRCC and support the recommendation to offer PN also in these patients.