Clinical, pathological and long-term oncologic outcomes of papillary type I vs. type II renal cell carcinoma

Despite papillary renal cell carcinoma (pRCC) subtype represents the second most common histological renal tumor, controversial findings have been shown regarding its prognosis. Thus, we investigated the natural history of patients harbouring pRCC, focusing on its clinicopathological characteristics and long-term oncologic outcomes among pRCC subtypes.

We identified 447 patients treated with either partial (PN) or radical nephrectomy (RN) for pRCC at a single tertiary centre, between 1994 and 2019. First, we explored differences in baseline and clinicopathological characteristics. Second, Kaplan-Meier plots investigated progression-free survival (PFS) and cancer-specific survival (CSS) differences among pRCC subtypes. Third, multivariable Cox-regression analyses (MVA) were used to assess predictors of clinical progression (CP) and cancer-specific mortality (CSM).

Overall, 120 (27%) patients had symptoms at time of diagnosis. 263 (58.8%) vs. 184 (41.2%) patients underwent PN vs. RN. At histopathological evaluation, 243 (54.4%) harboured pRCC type I vs. 204 (45.6%) type II. pRCC type II more frequently showed higher tumor grade, tumor necrosis or lymphovascular invasion (all P<0.001). After a median follow-up of 51 months, 2.5% and 11% of patients had local relapse and CP, respectively. Kaplan-Meier plots revealed 93 vs. 83% 5-year PFS (P<0.001) and 96 vs. 89% 5-year CSS (P=0.01) for non-metastatic pRCC type I vs. II, respectively. At MVA, pRCC type II predicted higher risk of CP (Hazard ratio [HR]: 3.03, 95%CI 1.42-6.44; P=0.01), as well as of CSM (HR: 2.60, 95%CI 1.05-6.29; P=0.02), relative to pRCC type I.

PRCC type II harbour more unfavorable tumor characteristics, such as higher tumor grade, more frequent tumor necrosis or lymphvascular invasion, which translates into worse long-term oncologic outcomes, compared with pRCC type I. Thus, patients harbouring pRCC type II may benefit from stricter follow-up, as well as earlier risk-based adjuvant therapies, based on potential worse oncologic outcomes in this patient population.