Unilateral Breast Cancer: Screening of Contralateral Breast by Using Preoperative MR Imaging Reduces Incidence of Metachronous Cancer

Abstract

To investigate the clinical effect of a single magnetic resonance (MR) imaging screening examination of the contralateral breast at preoperative evaluation in women with unilateral breast cancer. The institutional review board approved this study and waived informed consent. Among women with unilateral breast cancer who underwent curative surgery from 2004 to 2008, 1323 women (mean age, 46.8 years; range, 18-81 years) underwent mammography and ultrasonography (US) alone (comparison group) between January 2004 and December 2006; 1771 consecutive women (mean age, 48.2 years; range, 22-85 years) underwent mammography, US, and MR imaging (contralateral MR imaging-screened group) between January 2007 and December 2008. The incidence of synchronous cancer and the incidence of metachronous cancer in the contralateral breast were compared between groups. Multivariate Cox analysis was performed. Median follow-up was 56 months (range, 13-94 months). Twenty-five synchronous contralateral cancers (13 invasive cancers, 12 ductal carcinomas in situ; mean invasive size, 14 mm [range, 1-35 mm]; 92% [12 of 13] of invasive tumors were node negative) were additionally detected with MR imaging in the MR imaging-screened group. The cumulative incidence of contralateral breast cancer at 45 months was 0.5% (nine of 1771) (95% confidence interval [CI]: 0.23%, 0.96%) for the MR imaging-screened group and 1.4% (18 of 1323) (95% CI: 0.81%, 2.14%) for the comparison group (P = .02). Contralateral MR imaging screening (hazard ratio, 0.37; 95% CI: 0.15, 0.92; P = .03) and estrogen receptor negativity (hazard ratio, 3.98; 95% CI: 1.60, 9.92; P = .003) were associated with risk of contralateral cancer diagnosis in multivariate analysis. A single MR imaging screening examination of the contralateral breast in women with unilateral breast cancer increased synchronous cancer detection and was associated with decreased diagnosis of metachronous contralateral cancer within 45 months.