Evidence from a BreastScreen cohort does not support a longer inter-screen interval in women who have no conventional risk factors for breast cancer.

OBJECTIVES: To determine screening outcomes in women who have no recorded risk factors for breast cancer. METHODS: A retrospective population-based cohort study included all 1,026,137 mammography screening episodes in 323,082 women attending the BreastScreen Western Australia (part of national biennial screening) program between July 2007 and June 2017. Cancer detection rates (CDR) and interval cancer rates (ICR) were calculated in screening episodes with no recorded risk factors for breast cancer versus at least one risk factor stratified by age. CDR was further stratified by timeliness of screening (<27 versus ≥27 months); ICR was stratified by breast density. RESULTS: Amongst 566,948 screens (55.3%) that had no recorded risk factors, 2347 (40.9%) screen-detected cancers were observed. In screens with no risk factors, CDR was 50 (95%CI 48-52) per 10,000 screens and ICR was 7.9 (95%CI 7.4-8.4) per 10,000 women-years, estimates that were lower than screens with at least one risk factor (CDR 83 (95%CI 80-86) per 10,000 screens, ICR 12.2 (95%CI 11.5-13.0) per 10,000 women-years). Compared to timely screens with risk factors, delayed screens with no risk factors had similar CDR across all age groups and a higher proportion of node positive cancers (26.1% vs 20.7%). ICR was lowest in screens that had no risk factors nor dense breasts in all age groups. CONCLUSIONS: Majority of screens had no recorded breast cancer risk factors, hence a substantial proportion of screen-detected cancers occur in these screening episodes. Our findings may not justify less frequent screening in women with no risk factors.

Radiographer technique: Does it contribute to the question of clip migration?

INTRODUCTION: Marker clips are commonly deployed at the site of a percutaneous breast biopsy. Studies have shown that displacement of the clip from the site of deployment is not uncommon. The objective of this study was to determine how much 'migration' could be seen with fixed structures within the breast tissue across three consecutive annual screening examinations, and therefore attempt to quantify how much of the reported clip migration could be due to radiographer technique. METHODS: Large, easily identified benign calcifications were measured by two investigators across three consecutive cycles of screening mammography. The position of the calcifications on the two standard mammographic views was measured in two planes. Other variables recorded included breast size and density, compression force used, and location of the benign calcifications within the breast. RESULTS: In 38% of cases, benign breast calcifications showed a mimicked movement of >15 mm in at least one plane. This was greatest in large breasts, those where fibroglandular tissue occupied less than 50% of the breast volume, and in the upper outer quadrant of the breast where mimicked movement >10 mm was noted in up to 90% of the larger breasts. CONCLUSION: Fixed immobile objects in the breast can appear to move a distance of >15 mm in up to 30% of cases. Clinically, some of what has previously been called marker 'migration' may be spurious and accounted for by differences in radiographic positioning techniques.