Subsequent Breast Cancer Risk Following Diagnosis of Atypical Ductal Hyperplasia on Needle Biopsy.

Importance: Atypical ductal hyperplasia (ADH) is a known risk factor for breast cancer. Published risk estimates are based on cohorts that included women whose ADH was diagnosed before widespread use of screening mammograms and did not differentiate between the methods used to diagnose ADH, which may be related to the size of the ADH focus. These risks may overestimate the risk in women with presently diagnosed ADH.

Objective: To examine the risk of invasive cancer associated with ADH diagnosed using core needle biopsy vs excisional biopsy.

Design: A cohort study was conducted comparing the 10-year cumulative risk of invasive breast cancer in 955 331 women undergoing mammography with and without a diagnosis of ADH. Data were obtained from 5 breast imaging registries that participate in the National Cancer Institute-funded Breast Cancer Surveillance Consortium.

Exposures: Diagnosis of ADH on core needle biopsy or excisional biopsy in women undergoing mammography.

Main Outcomes and Measures: Ten-year cumulative risk of invasive breast cancer.

Results: The sample included 955 331 women with 1727 diagnoses of ADH, 1058 (61.3%) of which were diagnosed by core biopsy and 635 (36.8%) by excisional biopsy. The mean (interquartile range) age of the women at diagnosis was 52.6 (46.9-60.4) years. From 1996 to 2012, the proportion of ADH diagnosed by core needle biopsy increased from 21% to 77%. Ten years following a diagnosis of ADH, the cumulative risk of invasive breast cancer was 2.6 (95% CI, 2.0-3.4) times higher than the risk in women with no ADH. Atypical ductal hyperplasia diagnosed via excisional biopsy was associated with an adjusted hazard ratio (HR) of 3.0 (95% CI, 2-4.5) and, via core needle biopsy, with an adjusted HR of 2.2 (95% CI, 1.5-3.4). Ten years after an ADH diagnosis, an estimated 5.7% (95% CI, 4.3%-10.1%) of the women had a diagnosis of invasive cancer. Women with ADH diagnosed on excisional biopsy had a slightly higher risk (6.7%; 95% CI, 3.0%-12.8%) compared with those with ADH diagnosed via core needle biopsy (5%; 95% CI, 2.2%-8.9%).

Conclusions and Relevance: Current 10-year risks of invasive breast cancer after a diagnosis of ADH may be lower than those previously reported. The risk associated with ADH is slightly lower for women whose ADH was diagnosed by needle core biopsy compared with excisional biopsy.