A comparison of the prognosis of papillary and clear cell renal cell carcinoma Evidence from a meta-analysis

Objective: To compare the prognosis of papillary and clear cell renal cell carcinoma (RCC) in order to determine the optimal follow-up and therapy for patients with RCC. Methods: A systematic search of Web of Science, EMBASE, Cochrane Library, and PubMed databases was conducted for articles published through July 30, 2018, reporting on a comparison of the prognosis of papillary RCC and clear cell RCC using the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Results: Of 1896 studies, 11 were considered for the evidence synthesis. A total of 35,832 patients were included. Of these patients, 6907 patients were diagnosed with papillary renal cell carcinoma, and 28,925 patients were diagnosed with clear cell renal cell carcinoma. The prognosis of papillary RCC was better than that of clear cell RCC (hazard ratio (HR) = 0.50; 95% confidence interval (CI) 0.45 to 0.56; P<.001; I-2=91.9%). A subgroup analysis indicated that papillary RCC was associated with better outcomes (HR = 0.76, 95% CI 0.50-1.16), and a trend toward a higher risk ofmortality was observed in patients with metastatic RCC presenting with papillary histology, but the difference was not statistically significant (HR = 1.12, 95% CI 0.71-1.76, P=.085). Pooled data suggested a lack of a significant difference between papillary RCC(p-RCC) type 1 and clear cell RCC (cc-RCC) (HR = 0.30, 95% CI 0.12-0.73, P=.085). The pooled HR for the prognosis of p-RCC type 2 compared to cc-RCC was 1.69 (95% CI 0.93-3.08; P=.032). Conclusion: Papillary RCC is associated with better outcomes than clear cell RCC in patients without metastases, but not in patients with metastases. Optimal follow-up or therapy for patients with RCC should be assigned according to the tumor stage and subtype.