Changes in Breast Cancer Risk Associated with Benign Breast Disease from 1967 to 2013.

Background: Benign breast disease (BBD) increases breast cancer (BC) risk progressively for women diagnosed with non-proliferative (NP) change, proliferative disease without atypia (PDWA), and atypical hyperplasia (AH). Leveraging data from 18,704 women in the Mayo BBD Cohort (1967-2013), we evaluated temporal trends in BBD diagnoses and how they have influenced associated BC risk over four decades.

Methods: BC risk trends associated with BBD were evaluated using standardized incidence ratios (SIRs) and age-period-cohort modeling across four eras-pre-mammogram (1967-1981), pre-core needle biopsy (CNB) (1982-1992), transition to CNB (1993-2001), and CNB era (2002-2013).

Results: With a median follow-up of 15.8 years, 9.9% of women were diagnosed with BC (invasive and/or DCIS). From the pre-mammogram era to the CNB era, we observed a significant increase in BC risk, rising from an SIR of 1.61 to 1.99. The proportion of proliferative BBD diagnoses (PDWA or AH) increased markedly over time (28.1% to 49.7%), as did the proportion of DCIS events (11% to 28%; chi-square p < .001). Within specific BBD categories, the risk of invasive BC increased modestly.

Conclusions: While absolute risk of BC within BBD categories remained stable, the relative risk of BC after BBD increased over time due to notable increases in higher risk BBD lesions, specifically PDWA and AH. These findings illustrate how evolving screening practices have changed the risk profile of BBD and should inform management strategies for patients with BBD in modern clinical settings.