Improved long‐term survival of corpus cancer in Japan: A 40‐year population‐based analysis

The incidence of uterine corpus cancer has been increasing globally due to increase in obesity. However, a detailed analysis of long‐term epidemiological trends of corpus cancer in Japan, where obesity is relatively minimal, has not been conducted. In this retrospective, population‐based study using the Osaka Cancer Registry, we analyzed 15 255 cases of corpus neoplasia registered between 1977 and 2016. We determined the age‐standardized incidence, mortality, relative survival and conditional survival rates, and the treatment trends for corpus cancer over the last 40 years in Japan. The age‐standardized incidence rate of corpus neoplasia increased sharply in 2000‐2011 (APC = 9.9, 95% CI: 8.4‐11.3), whereas the mortality rate trended to a much more modest increase (APC = 3.3, 95% CI: 2.7‐3.8). Compared to 1977‐2000, 10‐year survival rates for post‐2000 cases of localized and regional corpus cancers significantly improved (from 87.7% [95% CI: 85.8‐89.4] to 94.2% [95% CI: 92.7‐95.7] and from 47.5% [95% CI: 43.3‐51.6] to 64.4% [95% CI: 61.0‐67.6], respectively). This was largely associated with the significant increase in the percentage of localized and regional patients who received chemotherapy instead of radiation as an adjuvant therapy combined to surgery (P < .001 for both). We found that each histological type (endometrioid carcinoma, serous carcinoma, clear cell carcinoma and carcinosarcoma) has different characteristics of trend of age‐standardized incidence rate, relative survival and distribution of extent of disease. In endometrioid carcinoma, the age‐standardized incidence rate increased consistently after 1990, but the rate of increase was decreasing after 1997.