Type and Extent of Surgery for Screen-Detected and Interval Cancers at Blinded Versus Nonblinded Double-Reading in a Population-Based Screening Mammography Program

Background. This study aimed to compare the type and extent of surgery in patients with screen-detected and interval cancers after blinded or nonblinded double-reading of screening mammograms.
Methods. The study investigated a consecutive series of screens double-read in either a blinded (n = 44,491) or nonblinded (n = 42,996) fashion between 2009 and 2011. During a 2 year follow-up period, the radiology reports, surgical correspondence, and pathology reports of all the screen-detected and interval cancers were collected.
Results. Screen-detected breast cancer was diagnosed for 325 women at blinded and 284 women at nonblinded double-reading. The majority of the women were treated by breast-conserving surgery (BCS) at both reading strategies (78.2 vs. 81.7 %; p = 0.51). Larger total resection volumes were observed at BCS for ductal carcinoma in situ (DCIS) treatment for patients after blinded double-reading (p = 0.005). The proportions of positive resection margins after BCS were comparable for patients with DCIS (p = 0.81) or invasive screen-detected cancers (p = 0.38) for the two reading strategies. A total of 158 interval cancers were diagnosed. The proportions of patients treated with BCS were comparable for the two reading strategies (p = 0.42). The total resection volume (p = 0.13) and the proportion of positive resection margins after BCS (p = 0.32) for invasive interval cancer were comparable for the two cohorts. The BCS rate was higher for women after nonblinded double-reading (p = 0.04).
Conclusions.  Blinded and nonblinded double-reading yielded comparable surgical treatments for women with screen-detected or interval breast cancer except for larger total resection volumes at BCS for screen-detected DCIS and a higher BCS rate for interval cancers at nonblinded double-reading.