Breast Density and Parenchymal Patterns as Markers of Breast Cancer Risk: A Meta-analysis by Valerie A. McCormack and Isabel dos Santos Silva Department of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, United Kingdom.
2006 American Association for Cancer Research.
A review of 42 articles for the main analysis. The 42 articles represent aggregate data for a total of 14,134 cases and 226,871 non-cases, arising from 17 incidence studies (6,967 cases) and 17 prevalence studies (4,983 cases) in the general population and 9 studies (2,184 cases) in symptomatic (breast cancer) populations (some studies contribute to more than one category).
- “This review explains some of the heterogeneity in associations of breast density with breast cancer risk and shows that, in well-conducted studies, this is one of the strongest risk factors for breast cancer.”
- “Breast density, a measure of the extent of radiodense fibroglandular tissue in the breast, has the potential to be used as a predictor of breast cancer risk, to monitor risk-lowering interventions and as an intermediate end point in studies of breast cancer etiology. More than 40 studies have assessed associations with Wolfe grade or percentage breast density and the majority reported 2-to-6-fold increased risks for the highest compared with the lowest risk categories…”
- “The combined data presented here confirm that breast density, measured using either Wolfe grade or percentage density, is strongly associated with breast cancer risk…”
- “The true association may be even stronger, as nondifferential measurement error of breast density would lead to underestimation of associations.”
- “We found little evidence of interactions between other risk factors for breast cancer and breast density. Importantly, the combined data suggest that breast density measured at both premenopausal and postmenopausal ages is a marker of subsequent breast cancer risk and that there is no clear evidence that the strength of this association differs between these ages.”
- “The strength of the association of breast density with breast cancer risk is greater than that for most other established breast cancer risk factors, with the exception of age and some genetic factors.”
- “…there was no threshold level below which density was not associated with risk. Shifting the entire breast density distribution downwards by a few percentage (if possible) might reduce overall breast cancer rates. Breast density may be amenable to change.”
- “Well-conducted incidence studies suggest that increasing breast density is associated with an increased risk of breast cancer and that the magnitude of this association is 4.64-fold (3.64-5.91) for the most dense (>75%) compared with the least dense category (<5%).”
- “This marker (breast density) has great potential to be used for research into the etiology and prevention of breast cancer.”