Determining risk-adapted starting age and interval for breast cancer screening based on reproductive and hormonal factors.

This study aimed to elucidate the risk of developing breast cancer (BC) by reproductive and hormonal profiles to suggest risk-adapted starting screening ages and to investigate risks after negative mammography results to inform screening intervals in the Korean setting. Participants who performed health examinations between 2002 and 2023 at the National Cancer Center were analyzed. Risk-adapted starting age of screening was defined as the age at which women with various reproductive and hormonal profiles obtained a 10-year cumulative risk level similar to women aged 40 years in the general population. The Cox progression model was used to assess BC risk according to the reproductive and hormonal score and time since the last negative mammography. Of the 24,597 women enrolled in this study, 606 had BC (median follow-up 13.2 years, IQR = 9.5-16.5 years). The 10-year cumulative risk of BC at age 40 years in general women was estimated at 2.35%. Women with different reproductive and hormonal profiles reached this risk level 8.55 years earlier to 4.61 years later. We found that women with various reproductive and hormonal profiles had similar incident cases in both low- and high-score groups beyond 5 years after a negative finding from mammography (p > .05), compared to those screened within 0 to <2 years after negative screening results. This study identifies possible risk-based starting ages for BC screening based on reproductive and hormonal factors. Our findings suggest that extending the current biennial screening interval beyond 5 years may still detect a comparable number of cases.