Screening for breast cancer in 2018-what should we be doing today?

Abstract

Although screening mammography has delivered many benefits since its introduction in Canada in 1988, questions about perceived harms warrant an up-to-date review. To help oncologists and physicians provide optimal patient recommendations, the literature was reviewed to find the latest guidelines for screening mammography, including benefits and perceived harms of overdiagnosis, false positives, false negatives, and technologic advances. For women 40-74 years of age who actually participate in screening every 1-2 years, breast cancer mortality is reduced by 40%. With appropriate corrections, overdiagnosis accounts for 10% or fewer breast cancers. False positives occur in about 10% of screened women, 80% of which are resolved with additional imaging, and 10%, with breast biopsy. An important limitation of screening is the false negatives (15%-20%). The technologic advances of digital breast tomosynthesis, breast ultrasonography, and magnetic resonance imaging counter the false negatives of screening mammography, particularly in women with dense breast tissue.

Keywords: Breast cancer; digital breast tomosynthesis; overdiagnosis; screening mammography.

FIGURE 1

Breast cancer (BCa) burden by age at diagnosis, 2007–2011. (A) Distribution of invasive female BCa cases (n = 292,369) by age at diagnosis. (B) Distribution of BCa deaths (n = 16,789, patients followed for up to 20 years) by age at diagnosis. (C) Distribution of person–years of life lost to BCa (n = 326,560, patients followed for up to 20 years) by age at diagnosis. Source: Oeffinger et al., 2015.

FIGURE 2

Locally advanced breast cancer in a 56-year-old woman, with calcifications seen at the same site 5 years earlier, likely an evolution from ductal carcinoma in situ (DCIS). (A) Bilateral digital mammograms demonstrate heterogeneously dense breasts (American College of Radiology, BI-RADS C), with a large spiculated mass in the central left breast causing left nipple retraction corresponding to the palpable mass. An ultrasound-guided breast biopsy (not shown) confirmed invasive ductal carcinoma, with axillary node metastases. (B) Maximal-intensity projection image from magnetic resonance imaging shows tumour occupying most of the left breast, measuring more than 5 cm. (C) Photographic enlargement of the left breast mass shows fine pleomorphic calcifications within the mass, characteristic for DCIS. (D) Photographic enlargement of the left breast from a screening mammogram 2 years earlier shows a smaller cluster of calcifications within the same area, not detected at screening. (E) Photographic enlargement of the left breast from a screening mammogram 5 years earlier shows a very small group of fine pleomorphic calcifications, likely DCIS, identified only in retrospect.