Trends in Incidence Rates, Mortality Rates, and Age-Period-Cohort Effects of Female Breast Cancer - China, 2003-2017.

Introduction: This study reported the trends in female breast cancer incidence and mortality rates in China, and analyzed the corresponding age-period-cohort effects.

Methods: Data from 22 population-based cancer registries in China between 2003 and 2017 were analyzed. Age-standardized incidence rates (ASIR) and mortality rates (ASMR) were calculated using Segi's world standard population. Joinpoint regression was employed to evaluate trends, and age-period-cohort effects were examined using the intrinsic estimator method.

Results: The ASIR for female breast cancer exhibited a more rapid increase in rural areas compared to urban areas across all age groups. The most substantial increase was observed in the 20-34 age group in rural areas [annual percent change (APC)=9.0%, 95% confidence interval (CI): 7.0%-11.0%, P<0.001]. The ASMR for females under 50 years old remained stable from 2003 to 2017 in both urban and rural areas. However, the ASMR for females over 50 in rural areas and those over 65 in urban areas demonstrated a significant increase, with the most pronounced increase observed among females over 65 in rural areas (APC=4.9%, 95% CI: 2.8%-7.0%, P<0.001). Age-period-cohort analysis revealed increasing period effects and decreasing cohort effects for female breast cancer incidence and mortality rates in both urban and rural settings. Notably, the cohort effect for incidence displayed a slight upward trend for females born between 1983 and 1992 in rural areas.

Conclusions: Our study revealed a rapid increase in breast cancer incidence among younger generations and an accelerated mortality rate in older populations residing in rural areas. To effectively address the growing burden of female breast cancer in China, it is essential to develop and implement targeted intervention strategies.