The Association of Mammographic Density and Molecular Breast Cancer Subtype
Menée aux Etats-Unis à partir de clichés mammographiques de patientes atteintes d'un cancer du sein entre 2003 et 2012, cette étude évalue l'association entre la densité mammaire et le risque de développer la maladie par sous-type histologique
Background: Mammographic density (MD) is associated with increased breast cancer risk, yet limited data exist on an association between MD and breast cancer molecular subtypes. Methods: Women ages 18 years and older with breast cancer and available mammograms between 2003 and 2012 were enrolled in a larger study on MD. MD was classified by the Breast Imaging Reporting and Data System (BI-RADS) classification and by volumetric breast percent density (Volpara Solutions). Subtype was assigned by hormone receptor status, tumor grade, and mitotic score (MS). Subtypes included: Luminal-A (ER/PR+ and grade = 1; ER/PR+ and grade = 2 and MS = 1; ER+/PR− and grade = 1; n = 233); Luminal-B (ER+ and grade = 3 or MS = 3; ER+/PR− and grade = 2; ER/PR+ and grade = 2 and MS = 2; n = 79); Her-2-neu+ (H2P; n = 59); triple-negative (ER/PR−, Her-2−; n = 86). Precancer factors including age, race, body mass index (kg/m2), family history of breast cancer, and history of lobular carcinoma in situ were analyzed. Results: A total of 604 patients had invasive cancer; 457 had sufficient information for analysis. Women with H2P tumors were younger (P = 0.011) and had the highest volumetric percent density (P = 0.002) among subgroups. Multinomial logistic regression (LA = reference) demonstrated that although quantitative MD does not significantly differentiate between all subtypes (P = 0.123), the association between MD and H2P tumors is significant (OR = 1.06; confidence interval, 1.01–1.12). This association was not seen using BI-RADS classification in bivariable analysis but was statistically significant (P = 0.047) when controlling for other precancer factors. Conclusions: Increased MD is more strongly associated with H2P tumors when compared with LA.