Temporal Trend of Breast Cancer Diagnoses in Young Women in Different Regions of Brazil from 2014 to 2022

Introduction: Breast cancer is the leading cause of female mortality in Brazil, and in young women, it generally presents more aggressively, with unfavorable characteristics, advanced stages, and a higher risk of recurrence. Objective: To analyze the temporal trend of diagnosed breast cancer cases in young women in different regions of Brazil from 2014 to 2022. Methods: An ecological time-series study using data from the Cancer Information System (SISCAN) of the Department of Informatics of the Unified Health System from 2014 to 2022. Reported cases of breast cancer according to ICD-10 C50 were included. For statistical analysis, standardized coefficients and simple linear regression were used. Results: An increasing trend in the overall diagnosis rate of breast cancer in young women (β=0.719; p<0.001). Increase in diagnoses in all regions, especially in the North region (β=0.888; p<0.001). Increment in all age groups, particularly among those aged 25 to 29 years, with the age group 40 to 44 years (β=1.817; p<0.001) having the highest rates. A major increase in cases of Carcinoma In Situ (β=0.047; p<0.001), with Ductal Carcinoma (β=0.394; p<0.001) being the most incident during the period. Conclusion: The data show an increase in the rate of breast cancer in young women in Brazil, across all regions, age groups, and histological types. This highlights the need for a better epidemiological understanding of the disease to develop strategies that reduce the associated morbidity and mortality.