False positives are associated with higher risk for subsequent breast cancer diagnoses. 

Previous research has suggested that false-positive mammogram results are associated with higher risk for subsequently developing breast cancer. To further examine this issue, researchers in Sweden used national mammography data to follow 500,000 women (median age, 52 years) during 30 years (1991 to 2020). About 45,000 women had false-positive results (i.e. they were recalled for further evaluation but did not receive diagnoses of breast cancer at that time). Women with false- positive results were matched with controls to compare rates of subsequent breast cancer diagnosis. The results include:

• women with false-positive results had a 20-year cumulative incidence of breast cancer of 11.3%, compared with 7.3% among controls (adjusted hazard ratio, 1.61)
• the association was strongest in women who were 60 to 76 years old, those with lower breast density and those who underwent biopsy with benign results at recall. (The authors note that abnormal findings in patients with low breast density are more likely to be truly pathological – rather than caused by obscuring effects of dense tissue)
• both ipsilateral and contralateral breast cancers were more common after false-positive results, but the association was strongest for ipsilateral cancers, especially in the first four years of follow up.

Comment: I discussed possible mechanisms for this association with a breast radiologist. She emphasised that ‘false-positive’ results include proliferative breast lesions (e.g. papilloma, atypical hyperplasia): although benign, these lesions are well-known markers of excess breast cancer risk. Current guidelines advise surgical excision of some high-risk lesions; other benign diagnoses might prompt more-frequent surveillance. Because these decisions can be quite nuanced, generalists should have a low threshold to consult a breast care specialist when false positives occur.

Molly S. Brett, MD, Assistant Professor of Medicine, University of Colorado, Boulder, USA.

Mao X, et al. Breast cancer incidence after a false-positive mammography result. JAMA Oncol 2024; 10: 63-70.

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine.