Abstract: Objective The aim of this study was to analyze the incidence and mortality of breast cancer in cancer registration areas of Yunnan Province in 2020 and the change trend of incidence and mortality from 2012 to 2020,so as to provide scientific basis for the formulation of prevention and control strategies and measures for breast cancer in Yunnan Province. Methods The incidence,mortality and related population data of female breast cancer cases included in the national registration annual report in cancer registration areas of Yunnan Province from 2012 to 2020 were collected.The statistical indicators such as incidence,mortality,age-standardized incidence rate by Chinese standard population(ASIRC),age-standardized mortality rate by Chinese standard population(ASMRC),age-standardized incidence rate by World standard population(ASIRW)and age-standardized mortality rate by World standard population(ASMRW)were calculated by urban and rural areas,and by age groups.The Joinpoint 4.8.0.1 software was used to analyze the trends in various indicators for the cancer registration areas in Yunnan Province from 2012 to 2020. Results In 2020,the incidence of female breast cancer in cancer registration areas of Yunnan Province was 24.95/100,000,ASIRC and ASIRW were 18.75/100,000 and 17.31/100,000,respectively.The incidence of the age group maintained at a low level before the age of 25,slow increase in the 25-39 age group,the 40-49 age group rose rapidly,and the 50-54 age group reached the peak(54.99/100,000),and then gradually declined with the increase of age.In 2020,the breast cancer mortality rate among women in the cancer registration regions of Yunnan Province was 5.89/100,000,with ASMRC of 3.93/100,000 and ASMRW of 3.80/100,000,respectively.The mortality in the age group was at a relatively low level before the age of 25,and then fluctuated with age after the age of 25,reaching its peak in the 75-79 age group(21.63/100,000).The incidence rates in urban and rural cancer registration areas were 20.76/100,000 and 18.00/100,000,respectively,while the mortality rates were 4.76/100,000 and 3.63/100,000,respectively(P＜0.001).From 2012 to 2020,the annual percentage change(APC)in the incidence rate and ASIRW of breast cancer among women in the cancer registration areas of Yunnan Province were -0.43%(95% CI:-3.71% to 2.95%)and -0.09%(95% CI:-3.83% to 1.93%),showing a trend of first increasing and then decreasing,but the trend was not statistically significant(P＞0.05);Mortality rates and age-standardized mortality rates showed a decreasing trend,with mortality rates decreasing from 10.22/100,000 in 2012 to 5.89/100,000 in 2020,with a statistically significant trend(APC=-6.21%,95% CI:-8.45% to -3.92%,P＜0.05),the age-standardized mortality rate decreased from 7.37/100,000 in 2012 to 3.80/100,000 in 2020,with a statistically significant trend(APC=-6.70%,95% CI:-9.21% to -4.13%,P＜0.05). Conclusions In 2020,the mortality rate of female breast cancer age group in cancer registration areas of Yunnan Province showed a fluctuating increase,and there was a difference in the incidence and mortality between urban and rural areas.They were higher in urban areas than those in rural areas,and the mortality and ASMRW from 2012 to 2020 showed a general downward trend.

Key words: Female, Breast cancer, Popular trend, Cancer registry, Yunnan Province