Prognostic Effect of Subclassification on Oncological Outcomes in Patients with Surgically Treated Localized Papillary Renal Cell Carcinoma: A Retrospective Propensity Score-matched Cohort Study

Background: Few studies have reported on whether the histological subclassification of papillary renal cell carcinoma (PRCC) affects postoperative oncological outcomes. This study aimed to compare the clinical and pathological characteristics and outcomes of type 1 and type 2 PRCC patients undergoing surgical treatment at our hospital and to investigate the effect of PRCC histological subclassification on clinical outcomes. Methods: We retrospectively analyzed the clinical and pathological data of 137 patients with PRCC who treated with surgery at our hospital between January 2007 and December 2020. Specifically, the clinical and pathological characteristics and oncological outcomes of 84 cases of type 1 PRCC and 53 cases of type 2 PRCC were analyzed. Propensity score matching was performed to minimize selection bias. The relationship between different subclassifications of PRCC and survival outcomes was applied by Kaplan-Meier survival analysis and multivariate Cox regression models. Results: Median follow-up was 35 months. The 5-year overall survival (OS), cause-specific survival (CSS), and progression-free survival (PFS) of patients with type 1 PRCC were 95.5%, 97.0%, and 89.4%, respectively. The 5-year OS, CSS, and PFS of patients with type 2 PRCC were 78.6%, 83.3%, and 66.7%, respectively. The unmatched cohort showed that type 2 PRCC was associated with larger tumor diameters and more tumor thrombi. In the unmatched and matched cohorts, univariate analysis showed that smoking, pathological subclassification of type 2, pathological grade of G3/G4, and combination with tumor thrombus appeared to affect the outcomes of PRCC patients (p < 0.05). Multivariate analysis showed that smoking, pathological subclassification of type 2, and pathological grade of G3/G4 were independent risk factors for poor oncological outcomes with PRCC (p < 0.05). OS, CSS, and PFS were lower in type 2 PRCC than in type 1 PRCC in the unmatched and matched cohorts (p < 0.05). In addition, 3-year and 5-year OS nomograms were constructed based on the multivariate analysis, and the calibrated concordance index was high, indicating good calibration and feasibility for clinical practice. Conclusion: Compared to type 1 PRCC, type 2 PRCC has significantly poorer OS, CSS, and PFS. History of smoking, histological subclassification, and pathological grade were independent predictors of oncological outcome. The nomogram based on histological subclassification was reliable for predicting the 3-year and 5-year OS of PRCC patients undergoing surgical treatment.