The value of routine screening mammography in women aged 35-39 years in a symptomatic breast unit

To determine the breast cancer detection rate at routine bilateral screening mammography in women aged 35-39 years attending a symptomatic breast clinic, in women of population-risk profile with a normal clinical examination.

A retrospective analysis of all mammograms performed on patients aged 35-39 years at St James's Hospital from 2011-2015 was carried out. Patients with moderate or high familial risk of breast cancer, personal breast cancer history or chest radiation, males, general practitioner (GP) and internal hospital referrals, and those with abnormal clinical examinations were excluded. Included women had "normal", "benign", or undocumented examination findings. Results of imaging, including ultrasound and histopathological results, were recorded. Information was extracted from the hospital's electronic record systems.

Of 4,087 patients aged 35-39 who had bilateral mammograms from 2011-2015, 2,148 patients were excluded from analysis. Of 1,939 included women, four (0.21%) were diagnosed with breast cancer confirmed at histology based on mammographic findings: two invasive ductal carcinoma (8 and 2 mm) and two ductal carcinoma in situ (DCIS; 4.5 mm high-grade DCIS and 2 mm low-grade DCIS). Other histological findings included two B3, 46 B2, and three B1 lesions. Overall, 115 biopsies were performed in this cohort; 55 (47.8%) were attributable to mammographic screening, producing a biopsy rate of 2.8% due to mammography alone.

Per 1,000 women screened, 2.1 cases of cancer were detected. This figure would be below accepted international thresholds to undertake screening mammography and raises radiation protection issues. Additionally, a large number of benign biopsies were undertaken, with likely resultant psychological impact. Further studies could inform national guidance.