(P-562) Prevalence of Extramammary Paget’s Disease in Urban China: A Population-based Study

Background: Extramammary Paget’s disease (EMPD) is an intraepithelial adenocarcinoma. The chronic relapsing clinical course and unbearable clinical symptoms of extramammary Paget’s disease usually result in a markedly diminished quality of life. No national data are available on descriptive epidemiology of EMPD in China, the most populous country over the world.

Objectives: This population-based study aimed to estimate the prevalence and associated sex and age patterns of EMPD in China.

Methods: This study was conducted using data from China’s Urban Employee Basic Medical Insurance and Urban Resident Basic Medical Insurance, covering approximately 0.43 billion Chinese urban residents in 2016. Patients with EMPD were identified based on the diagnostic names and codes in claim data. The prevalence of EMPD was estimated by sex, age, and geographical region (East, North, Northeast, Northwest, Southcentral, and Southwest) as well. Based on the 2010 Chinese national census data, the Revised European Standard Population (RESP) 2013, the 2010 US population and the 2011 Australian population, age-adjusted rates of EMPD prevalence were provided. The unit for annual prevalence was per 100 000 population. Prevalence with 95% confidence interval (CI) was estimated by Poisson distribution.

Results: A total of 53 males and 31 females with EMPD were found. The crude prevalence in 2016 was 0.04 per 100 000 population [95% confidence interval (CI): 0.02 to 0.06], ranging from 0.01 (95% CI: 0.00 to 0.02) in North or Northeast China to 0.08 (95% CI: 0.03 to 0.16) in Southwest China. The rates were higher in males (0.05, 95% CI: 0.03 to 0.08) compared with females (0.03, 95% CI: 0.02 to 0.05). The mean age of patients was 65.87 (standard deviation: 14.21) years, with the peak prevalence appeared in patients aged 70-79 (0.28, 95% CI: 0.16 to 0.42). The age-adjusted national prevalence based on 2010 Chinese census data was 0.04 per 100 000 population (95% CI: 0.04 to 0.05). The standardized prevalence rates by the US, European and Australian populations were 0.05 (95% CI: 0.05 to 0.06), 0.07 (95% CI: 0.06 to 0.08) and 0.06 (95% CI: 0.05 to 0.06), respectively.

Conclusions: The prevalence of EMPD was markedly lower than those in the United States and Europe, and varied across regions in China. Chinese patients were much younger, with significant male predominance. Further studies are warranted to examine potential pathophysiologic mechanism.