Objective Ultrasound categories of Breast Imaging Reporting and Data System (BI-RADS) are an important outcome used in the evaluation of the characteristics of breast lesions. In this study, we aim to explore the potential influencing factors that may cause the progression of BI-RADS categories.

Methods Based on the cervical cancer and breast cancer screening cohort in Shuangliu District, Chengdu from 2015 to 2021, we collected ultrasound and questionnaire results. Progression was defined as changing from BI-RADS category 1 or 2 to 3 or above, or from the initial screening result of BI-RADS 3 or above to a higher category in subsequent ultrasound screenings. The Cox proportional hazards regression model was used to explore potential influencing factors for BI-RADS classification progression. A restricted cubic spline was used to explore the nonlinear association between the variables and the risk of progression.

Results A total of 7069 participants were included in the analysis and followed up for 23580 person-years. Compared with other age groups, the proportion of participants of BI-RADS category 3 and above was highest in the 40-44 age group (24.83%). Cox regression analysis showed that postmenopausal women had a lower risk of BI-RADS progression than premenopausal women did (hazard ratio HR: 0.65, 95% confidence interval CI: 0.44-0.97). In postmenopausal women, late menopause (HR=1.16, 95% CI: 1.03-1.30) was identified as a risk factor for BI-RADS progression. Obesity in premenopausal women was negatively associated with the risk of progression (HR=0.43, 95% CI: 0.21-0.88).

Conclusion The risk factors for progression in ultrasound BI-RADS categories overlap with the risk factors for breast cancer. A risk score based on the high-risk factors for BI-RADS progression can be constructed to optimize screening programs for high-risk populations and improve the efficiency of breast cancer screening.