Abstract:

Background and purpose: The Shanghai Municipal Center for Disease Control and Prevention provides annual updates on cancer statistics in Shanghai. Breast cancer is one of the common malignant tumors among women. In recent years, the incidence of female breast cancer was increasing, while its trend of mortality showed declining. This study aimed to investigate the survival rates of new female breast cancer cases in Shanghai from 2002 to 2017. Methods: Data of new cases and deaths of female breast cancer patients with follow-up information from 2002 to 2017 were obtained from the Population-based Cancer Registry and Vital Statistics System of Shanghai Municipal Center for Disease Control and Prevention. Numbers, proportions, and survival rates were stratified by year of diagnosis, age, histological type and stage at diagnosis for analysis. The 5-year observed survival rates were calculated based on the life table method. The probabilities of surviving from 0 to 99 years were estimated with the Elandt-Johnson model, and then cumulative expected survival rates were calculated using the Ederer Ⅱ method. Finally, the 5-year relative survival rates were calculated. The annual percent change (APC) of survival rates was estimated by Joinpoint Regression Program. Results: A total of 73 600 new female breast cancer cases were diagnosed from 2002 to 2017 in Shanghai. Among them, 67 681 cases were morphological verification, accounting for 91.96%. By December 31, 2022, 23 745 (32.26%) cases had died, and 19 466 (26.45%) cases had died of cancer. A total of 68 332 (92.84%) cases, who were either dead or followed for over 5 years, were considered to have complete follow-up. The remaining 5 268 (7.16%) cases were lost to follow-up. 73 538 (99.92%) cases were included in the observed cohort for survival analysis. The number of observed cases nearly doubled from 3330 in 2002 to 6095 in 2017. The 5-year observed survival rate changed from 78.77% in 2002 to 84.55% in 2017 dynamically, showed a low increasing trend with an average rate of 0.50% per year (APC=0.50%, t=8.75, P<0.001). The 5-year relative survival rate also increased from 83.46% to 89.24% slowly, with an average rate of 0.47% (APC=0.47%, t=9.80, P<0.001). The overall 5-year observation survival rate of female cancer was 83.24% (82.96%-83.52%), and the 5-year relative survival rate was 87.58% (87.29%-87.87%) in Shanghai from 2002 to 2017. It was increasing over time, decreasing with aging and advanced stage at diagnosis continuously. There was no significant difference in the 5-year relative survival rates between the groups aged 15 to 64 (P>0.05). The group with an unknown stage had the highest number of cases, followed by the stage Ⅱ group, and then the stage Ⅰ group. The 5-year relative survival rate of cases with stage Ⅰ disease reached 99.10% (98.78%-99.42%), but these cases only accounted for 25.51% of the total. The 5-year relative survival rate of cases with stage Ⅳ disease was 52.54% (50.98%-54.11%), and these cases accounted for 6.13% of the total. The 5-year relative survival rate of cases with s unknown stage was 82.04% (81.42%-82.65%), and these cases accounted for 31.05% of the total. Conclusion: The diagnostic levels and survival rates of female breast cancer in Shanghai were relatively high and continue to improve. However, the proportions of cases with unknown histological type and unknown stage remain relatively high, and the proportion of stage Ⅰ cases is not very large. The survival rates of stage Ⅳ cases are relatively low. This study provides evidence for further research, prevention and control efforts for female breast cancer.

Key words: Breast Cancer, Survival, Epidemiology, Shanghai