Sex‐specific analysis of renal cell carcinoma histology and survival in Japan: A population‐based study 2004 to 2016

BACKGROUND AND AIMS: In Western countries, sex differences in renal cell carcinoma (RCC) histology and survival have been previously described: compared with men, clear cell subtype is more common but overall prognosis is better among women. The goal of the present study was to examine sex differences in RCC histology and survival in Japan, using a large‐scale population‐based data set. METHODS: With the use of a population‐based cancer registry in Japan (2004‐2016), patients with primary RCC were followed for 5 years (median follow‐up time 2.1 years). We distinguished histological subtypes of clear cell, papillary, and chromophobe from “others” subtype. Sex‐specific prevalence ratio (PR) for each histological subtype was estimated by Poisson regression with robust variance, adjusted for age and year of diagnosis. Sex‐specific survival rates were estimated by Cox proportional hazard regression, adjusted for age, year of diagnosis, histological subtypes, and other prognostic variables, with multiple imputation. RESULTS: The prevalence of clear cell and “others” subtypes was similar between men and women among all the 5265 study subjects during the 12 years of study (clear cell, male 88.6% vs female 87.1%; “others“, male 5.3% vs female 5.3%). However, papillary subtype was less common among women than men (male 4.6% vs female 2.8%; PR = 0.63; 95% CI, 0.45‐0.88), while chromophobe subtype was more common among women (male 1.6% vs female 4.8%; PR = 3.18; 95% CI, 2.26‐4.47). Although “others” subtype (but not papillary/chromophobe subtypes) independently predicted prognosis (HR = 1.74; 95% CI, 1.32‐2.30), no sex differences were observed in RCC survival. CONCLUSION: We did not observe a statistically significant difference in the prevalence of clear cell subtype between men and women in Japan, which differs from the pattern previously described in Western countries. Sex differences in RCC histology may not affect RCC survival in this population.