Mammographic changes resulting from benign breast surgery impair breast cancer detection at screening mammography

Purpose: To study possible explanations for lower screening performance after previous benign breast surgery. Patients and methods: We included a consecutive series of 351,009 screening examinations in 85,274 women, obtained between January 1, 1997 and January 1, 2009. The examinations of women with screen detected cancers (SDC) or interval cancers (IC), diagnosed after previous benign breast surgery, were reviewed by two screening radiologists. They determined the presence and degree of post surgical changes, classified breast density and determined whether mammographic interpretation was hampered by tissue characteristics. They also assessed whether the cancer had already been visible at a previous screen. Results: Screening sensitivity was lower in women with prior benign breast surgery than without (63.5% (115/181) versus 73.5% (1643/2236), p = 0.004). A total of 115 SDCs and 66 ICs were diagnosed in breasts after previous benign breast surgery. Post surgical mammographic alterations in the breast segment where cancer was diagnosed were more distinct in ICs than in SDCs (p = 0.001). Women with post surgical mammographic changes at the location of the breast cancer had an increased interval cancer risk (OR = 2.12, 95% confidence interval (CI) = 1.05-4.26). Limited mammographic interpretation due to tissue characteristics was mentioned, only in three SDCs and one IC. The proportions of SDCs and ICS that were already visible at a previous screen were comparable for women with and without prior surgery (SDC: 47.5% versus 43.8%, p = 0.3, IC: 50.0% versus 48.4%, p = 0.8). Conclusion: Previous benign breast surgery decreases screening sensitivity and this is likely due to postoperative mammographic changes.