Breast cancer was the most commonly diagnosed invasive cancer and the second leading cause of cancer mortality among women in Ireland during 2020–2022. The strongest risk factors for breast cancer are female sex and increasing age. Other risk factors include hormonal and reproductive factors, breast density, hereditary and genetic factors, alcohol consumption, body mass index, and environmental exposures. 

Breast cancer screening aims to reduce breast cancer morbidity and mortality among asymptomatic women through earlier detection and treatment of the cancer. In Ireland, BreastCheck, the national population-based breast screening programme, invites eligible asymptomatic women aged 50 to 69 years for a mammogram every two years.

Breast density refers to the amount of fibroglandular (dense) tissue relative to the amount of adipose (fatty) tissue in the breast. On a mammogram, dense tissue appears white, similar to breast cancer tumours, while adipose tissue appears dark. This means that, as well as being a risk factor for developing breast cancer, high levels of breast density can mask the appearance of breast cancers on a mammogram, thereby reducing the sensitivity of mammography for women with dense breasts. 

Breast density is not currently measured as part of the BreastCheck screening programme, but can be measured using visual, semi-automated, and automated methods. Visual methods involve a radiologist visually assessing breast tissue composition on a mammogram. Semi-automated and automated breast density measurement tools involve computer-based methods with the aim of making measurement more consistent and standardised. 

Internationally, there has been increased interest regarding the introduction of screening pathways for women with dense breasts. These may include measuring, recording and notifying women of their breast density. Women with dense breasts could potentially be offered additional screening tests, such as digital breast tomosynthesis, MRI, contrast enhanced mammography, or ultrasound.

This HTA was requested by the National Screening Advisory Committee (NSAC). It will consider ways in which breast density could be included within the BreastCheck screening pathway and will support the National Screening Advisory Committee in making a recommendation to the Minister for Health on this topic. This assessment is being carried out as part of a larger piece of work that will also evaluate potential age extensions to the BreastCheck programme. A separate protocol will outline the approach to the assessment of extending BreastCheck to women aged 45 to 49 years and 70 to 74 years.