Calcifications in Digital Mammographic Screening: Improvement of Early Detection of Invasive Breast Cancers?

Abstract

To evaluate the relevance of calcifications for invasive breast cancer detection in population-based digital mammographic screening. This study was approved by an independent ethics committee, and no additional informed consent was required. Prospectively documented radiologic cancer features were correlated with pathologic characteristics in 241 breast malignancies diagnosed in 24067 participating women aged 50-69 years (part of the digital German Screening Program; initial screening rate, 92%; detection rate [DR], 1.0%; recall rate [RR], 7.5%). The rates of invasive cancers detected on the basis of calcifications were analyzed against pathologic tumor categories (pT categories) and histologic grades. For comparison of the study data with results of analog screening, data from the literature regarding calcification-specific RR, DR, and positive predictive value for recall (PPV(1)) were calculated. The calcification-specific RR was 1.7% (416 of 24067). The calcification-specific DR for invasive cancer was 0.12% (29 of 24067), and the PPV(1) was 7.0% (29 of 416). Of all malignancies detected on the basis of calcification, 38% (29 of 77) were invasive. pT1 cancers showed an inverse association between tumor size and rate of detection on the basis of calcification; differences in rates among pT1 subcategories were statistically significant (P < .001). The proportion of grade 1 pT1 cancers detected on the basis of calcification (eight of 27) did not differ significantly from that of cancers detected on the basis of other radiologic features (46 of 108, P = .24). The calcification-specific invasive cancer DR was significantly higher for digital than for analog mammography. One-third of malignancies detected on the basis of calcifications only are invasive cancers. They tend to be smaller but not less aggressive than invasive cancers detected on the basis of other features. Compared with published results of analog screening, digital screening offers the potential to increase the rate of invasive cancers detected on the basis of calcifications in population-based mammographic screening.