Is Repetition of the Contralateral Mammogram of Patients Referred for Unilateral Findings from the Dutch Breast Cancer Screening Necessary?

Objective: To determine the benefit of contralateral mammogram repetition in patients referred from the Dutch breast cancer screening program for unilateral findings. Material and Methods: 395 patients were referred from screening to our institution for unilateral findings between October 2009 and August 2011. In all patients a bilateral mammogram was repeated and analyzed by experienced breast radiologists. Anonymised data concerning the date of registration of the screening mammogram, the referred side (left/right or bilateral), age, screening’s BI-RADS classification, breast density, biopsy results and follow-up were collected. Results: Of the 395 patients referred for a suspicious unilateral finding, a malignancy on the referred breast was confirmed in 144 patients. In addition, a malignancy in the contralateral breast was diagnosed in six patients (1.5%). One of these six contralateral malignancies was occult on screening mammogram, but depicted on institutional mammogram only. The remaining five cases were detected in a blinded retrospective analysis by an experienced radiologist and were considered overlooked by the screening radiologists. During follow-up (mean 27.8 months), no contralateral malignancies were detected. Conclusion: Repetition of the two-view mammogram of the contralateral side in patients referred with a unilateral suspicious finding seems unnecessary.