Morphologic subtyping as a prognostic predictor for survival in papillary renal cell carcinoma: Type 1 vs. type 2

Objective: To evaluate outcomes of surgically treated patients with clinically localized papillary renal cell carcinoma (RCC) and determine if papillary RCC subtype is associated with recurrence and survival.

Methods: This is a historical cohort study using the prospectively maintained Canadian Kidney Cancer Information System database between January 2011 and September 2018. All patients underwent partial or radical nephrectomy. Patient, tumor, treatment, and outcomes were compared between papillary RCC type 2 and type 1 cohorts.

Results: During the study period, 509 patients had clinically localized papillary RCC type 2 (n = 172) or type 1 (n = 337) histology. Sex, race, and comorbidities were similar between groups. Pathologic stage (pT3 or pT4), nuclear grade (3 or 4), and tumor diameter were higher in the type 2 papillary RCC cohort (P < 0.0001). A greater proportion of type 2 papillary RCC patients received radical nephrectomy (42.4% vs. 24.6%, P< 0.0001). More type 2 papillary RCC patients underwent lymph node dissection (19.6% vs. 5.5%, P< 0.0001) and had lymph node metastases removed during surgery (6.4% vs. 0.6%, P= 0.103). Overall, adjusting for age, grade, pathologic stage, positive nodes, and tumor size, type 2 papillary RCC had worse outcomes compared to type 1, as demonstrated by elevated all-cause mortality (hazard ratio = 7.7 [95% confidence interval: 2.0-28.9]), P=0.0027) and worse recurrence-free survival (hazard ratio = 8.2 [95% confidence interval: 3.6-19.0], P< 0.0001).

Conclusion: Patients with clinically localized type 2 papillary RCC present with higher risk disease and have worse prognosis compared to patients with clinically localized type 1 papillary RCC. To the best of our knowledge, this is the largest cohort study comparing papillary RCC subtypes.