Mammographic Breast Density and Subsequent Risk of Breast Cancer in Postmenopausal Women according to the Time Since the Mammogram
A partir des données de l'étude "Nurses' Health Study" incluant 1 028 cas et 1 780 témoins, cette étude évalue l'association entre la densité mammaire et le risque de cancer du sein chez des femmes ménopausées selon le temps écoulé depuis leur dernière mammographie
Background. Few studies have shown that the association between mammographic breast density and breast cancer persists for up to 10 years after the mammogram. We investigated associations of percent density, absolute dense and non-dense areas with breast cancer risk according to the time since the mammogram. Methods. This study included 1,028 incident breast cancer cases diagnosed within the Nurses' Health Study and 1,780 matched controls. Breast density was measured from digitized film images with computerized techniques. Information on breast cancer risk factors was obtained prospectively from the biennial questionnaires before the date of cancer diagnosis for cases and their matched controls. The data were analyzed with logistic regression. Results. Breast cancer risk increased with increasing percent density and increasing absolute dense area and decreased with increasing non-dense. In multivariate analysis, the magnitude of the association between percent density and breast cancer was similar when the time since the mammogram was <2, 2-<5, and 5-<10 years (density ≥50% vs.<10%: ORs 3.12 [95%CI 1.55-6.25], 5.35 [95%CI 2.93-9.76], and 3.91 [95%CI 2.22-6.88], respectively). Similarly, the magnitude of association between quartiles of dense and non-dense areas and breast cancer risk were similar across the time strata. We found no interactions between the time since the mammogram and breast density measures (p for all interactions>0.05). Conclusions. Patterns of the associations between percent density, absolute dense and non-dense area with breast cancer risk persist for up to 10 years after the mammogram. Impact. A one-time density measure can be used for long-term breast cancer risk prediction.