Original Title: État des connaissances: Densité mammographique et dépistage du cancer du sein

Authors' objectives: Mammographic density refers to the fibroglandular component of the breast, which appears radiopaque on mammography. In the screened population, 10% of women have breasts that are almost entirely fatty, 40% have scattered areas of fibroglandular density, 40% have heterogeneously dense breasts, and 10% have extremely dense breasts. Several studies have suggested that mammographic density increases the risk of developing breast cancer and also reduces mammographic sensitivity. To determine whether mammographic density constitutes a significant risk factor and whether it should warrant personalized screening for women with extremely dense breasts, the Ministère de la santé et des services sociaux (MSSS) asked the Institut national d’excellence en santé et en services sociaux (INESSS) to prepare a state-of-knowledge report on this subject.

Authors' results and conclusions: RESULTS: 1. (Mammographic density and cancer risk) - • Mammographic density is associated with an increased risk of breast cancer; • The risk of interval cancer increases with the presence of mammographically visible dense tissue because of the masking effect of density, which reduces mammographic sensitivity; • Among other factors, the magnitude of the risk in the different studies varies according to the adjustment for confounding factors, the definition used for dense breasts, and the composition of the reference group. For this reason, the magnitude of the risk (of developing cancer and of cancer escaping detection by screening) is uncertain. 2. (Frequency of screening mammography in women with extremely dense breasts) - • There are insufficient data on the performance of various digital mammography screening intervals in women with extremely dense breasts; • The reduced sensitivity of mammography in this population suggests that using more sensitive supplemental imaging modalities may be a more effective screening strategy than changing mammogram frequency. 3. (Supplemental imaging following a negative screening mammogram in women with extremely dense breasts) - • No study has examined the efficacy of ultrasound specifically in women with extremely dense breasts and a negative screening mammogram. Consequently, the efficacy of breast ultrasound in this population is not known; • The available evidence concerning the use of magnetic resonance imaging (MRI) in women with extremely dense breasts who have a negative screening mammogram is limited; • Compared to digital mammography, combo mode tomosynthesis (3D + 2D) would not improve the cancer detection rate or the recall rate in women with extremely dense breasts; • Several studies evaluating different screening approaches for women with dense breasts are currently underway. 4. (Guidelines) - • Most of the recommendations found were made for the group of women with either heterogeneously dense or extremely dense breasts; • In general, there are no evidence-based consensus guidelines for breast cancer screening in women for whom mammographic density is the only risk factor; • Most of the sources consulted have nonetheless taken a position against personalized density-based screening because of the lack of available data to judge the impact of modalities that are alternatives or complementary to screening mammography on clinical outcomes. LIMITATIONS: The mandate from MSSS only concerned women with extremely dense breasts. An analysis that includes women with heterogeneously dense breasts could yield different findings. This exclusion and its associated implications were, in fact, highlighted by some of the experts consulted for the project.

Authors' recommendations: WARNING: It is important to note that, despite reduced mammographic sensitivity in women with extremely dense breasts, this modality is still the gold standard for breast cancer screening. Like all other women, those with extremely dense breasts should participate in the screening program and be attentive to observed changes. Women who experience symptoms must consult a physician, even if their last screening mammogram was normal (Quebec Breast Cancer Screening Program).

Project Status: Completed

URL for project: https://www.inesss.qc.ca/publications/repertoire-des-publications/publication/densite-mammographique-et-depistage-du-cancer-du-sein.html

Year Published: 2021

URL for published report: https://www.inesss.qc.ca/publications/repertoire-des-publications/publication/densite-mammographique-et-depistage-du-cancer-du-sein.html

English language abstract: An English language summary is available

Publication Type: Other

Country: Canada

Province: Quebec

Organisation Name: Institut national d'excellence en sante et en services sociaux

Contact Address: L'Institut national d'excellence en sante et en services sociaux (INESSS) , 2021, avenue Union, bureau 10.083, Montreal, Quebec, Canada, H3A 2S9;Tel: 1+514-873-2563, Fax: 1+514-873-1369

Contact Name: demande@inesss.qc.ca

Contact Email: demande@inesss.qc.ca

Copyright: Gouvernement du Québec