Historical Trends in Incidence of Breast Cancer in Shanghai, Hong Kong and Los Angeles, 1973-2012: A Joinpoint and Age-Period-Cohort Analysis

Objectives: This study aimed to estimate the long-term trends of breast cancer incidence in Shanghai, Hong Kong, and Los Angeles (LA). Methods: Data were obtained from Cancer Incidence in Five Continents (CI5plus) database. The average annual percent change (AAPC) was conducted by joinpoint regression analysis, and the age, period and cohort effects were estimated by age-period-cohort (APC) analysis. Results: The age-standardized incidence rates (ASIRs) in LA were higher than Shanghai and Hong Kong. During 1988-2012, the ASIRs significantly decreased in white women in LA (AAPC = -0.6%, 95% CI: -0.9% to -0.4%) while increased in Shanghai (2.5%: 2.1%-2.9%) and Hong Kong (2.2%: 2.0%-2.5%). The APC analysis revealed significantly increased effects of age and period, and decreased effect of birth cohort. Conclusion: Although age and cohort effects were relatively strong, the period effect may be the key factor affecting trends of incidence, which may be caused by increasing exposures to carcinogens and risk factors. Therefore, more effective measures should be carried out promptly to protect high-risk populations such as elder women, to avoid exposures to risk factors of breast cancer.