Causes and consequences of delayed diagnosis in breast cancer screening with a focus on mammographic features and tumour characteristics.

PURPOSE: To study the prevalence, causes and consequences of delayed breast cancer diagnosis in the screening population. METHODS: This retrospective study was performed in women who underwent biennial screening mammography between January 1, 2009 and June 30, 2019. Patients were divided into 3 groups; screen-detectedbreast cancer (SDC) without a diagnostic delay, a primary diagnostic delay(i.e. missed cancer at previous screening round)and a delay in diagnostic work-up after recall. Women with a true interval cancer (IC; i.e. not visible on prior examinations) were excluded. Outcome parameters included mammographic and tumour characteristics, lymph node status and surgical treatment. RESULTS: In our sample of 4491 women with breast cancer (4292 SDC and 199 'missed' IC), respectively, a total of 1112 women experienced a diagnostic delay of ≥ 4 months. Compared to women without a diagnostic delay (n = 2720), the 176 women with a delay in diagnostic work-up showed overall similar mammographic abnormalities (P = 0.052). These groups show similar distributions in invasive tumours, tumour stage and lymph node status (P = 0.25, P = 0.95 and P = 0.93, respectively). Women with a primary diagnostic delay (n = 936) showed less calcifications (P < 0.001), and more masses with calcifications and architectural distortions on mammography (P = 0.01 and P = 0.04, respectively). Moreover, this group comprised larger tumours (P < 0.001) and lymph node metastases (P < 0.001), and more often underwent mastectomy (P < 0.001). CONCLUSIONS: A primary diagnostic delay in breast cancer diagnosis results in less favourable tumour characteristics and relatively more mastectomies compared to no delay in breast cancer diagnosis and a delay in diagnostic work-up after recall.

International Interobserver Variability of Breast Density Assessment.

PURPOSE: The aim of this study was to determine variability in visually assessed mammographic breast density categorization among radiologists practicing in Indonesia, the Netherlands, South Africa, and the United States. METHODS: Two hundred consecutive 2-D full-field digital screening mammograms obtained from September to December 2017 were selected and retrospectively reviewed from four global locations, for a total of 800 mammograms. Three breast radiologists in each location (team) provided consensus density assessments of all 800 mammograms using BI-RADS® density categorization. Interreader agreement was compared using Gwet's AC2 with quadratic weighting across all four density categories and Gwet's AC1 for binary comparison of combined not dense versus dense categories. Variability of distribution among teams was calculated using the Stuart-Maxwell test of marginal homogeneity across all four categories and using the McNemar test for not dense versus dense categories. To compare readers from a particular country on their own 200 mammograms versus the other three teams, density distribution was calculated using conditional logistic regression. RESULTS: For all 800 mammograms, interreader weighted agreement for distribution among four density categories was 0.86 (Gwet's AC2 with quadratic weighting; 95% confidence interval, 0.85-0.88), and for not dense versus dense categories, it was 0.66 (Gwet's AC1; 95% confidence interval, 0.63-0.70). Density distribution across four density categories was significantly different when teams were compared with one another and one team versus the other three teams combined (P < .001). Overall, all readers placed the largest number of mammograms in the scattered and heterogeneous categories. CONCLUSIONS: Although reader teams from four different global locations had almost perfect interreader agreement in BI-RADS density categorization, variability in density distribution across four categories remained statistically significant.

Comparison of digital screening mammography and screen-film mammography in the early detection of clinically relevant cancers: a multicenter study.

PURPOSE: To compare screen-film mammography with digital mammography in a breast cancer screening program, with a focus on the clinical relevance of detected cancers. MATERIALS AND METHODS: The study was approved by the regional medical ethics review board. Informed consent was not required. Before the nationwide transition to digital mammography in the Dutch biennial screening program, the performance of digital mammography was studied in three screening regions. For initial screening examinations, mediolateral oblique and craniocaudal views were obtained of each breast. In subsequent examinations, the mediolateral oblique view was standard. A craniocaudal view was added if indicated. Screening outcomes obtained with screen-film mammography and digital mammography, including radiologic and pathologic characteristics, were compared for initial and subsequent examinations. RESULTS: A total of 1,198,493 screening examinations were performed between 2003 and 2007. Recall was indicated in 18 896 cases (screen-film mammography: 2.6% at initial examinations, 1.3% at subsequent examinations; digital mammography: 4.4% at initial examinations, 2.1% at subsequent examinations; P < .001 for both). Breast cancer was diagnosed in 6410 women (detection rate per 1000 women with screen-film mammography: 5.6 at initial examinations, 5.2 at subsequent examinations; detection rate per 1000 women with digital mammography: 6.8 at initial examinations, 6.1 at subsequent examinations; P = .02 and P < .001, respectively). Digital mammography depicted significantly more ductal carcinoma in situ (DCIS) lesions, irrespective of screening round. Invasive carcinoma was detected significantly more often in subsequent examinations, particularly when associated with microcalcifications (P = .047). The distribution of the histopathologic differentiation grades for DCIS and invasive carcinoma were similar with both modalities. However, with digital mammography more high-grade DCIS lesions were detected at subsequent examinations (P = .013). CONCLUSION: In a population-based breast screening program, the performance of digital mammography in the detection of DCIS and invasive carcinoma was substantially better than that of screen-film mammography. There is no sign of an increase in detection of low-grade DCIS lesions-indicative of possible overdiagnosis-with digital breast cancer screening. Rather, digital mammography appears to add to the detection of high-grade DCIS.

Consequences of digital mammography in population-based breast cancer screening: initial changes and long-term impact on referral rates.

OBJECTIVES: To investigate the referral pattern after the transition to full-field digital mammography (FFDM) in a population-based breast cancer screening programme. METHODS: Preceding the nationwide digitalisation of the Dutch screening programme, an FFDM feasibility study was conducted. Detection and referral rates for FFDM and screen-film mammography (SFM) were compared for first and subsequent screens. Furthermore, radiological characteristics of referrals in digital screening were assessed. RESULTS: A total of 312,414 screening mammograms were performed (43,913 digital and 268,501 conventional), with 4,473 consecutive referrals (966 following FFDM). Initially the FFDM referral rate peaked, and many false-positive results were noted as a consequence of pseudolesions and increased detection of (benign) microcalcifications. A higher overall referral rate was observed in FFDM screening in both first and subsequent examinations (p < .001), with a significant increase in cancer detection (p = .010). CONCLUSION: As a result of initial inexperience with digital screening images implementing FFDM in a population-based breast cancer screening programme may lead to a strong, but temporary increase in referral. Dedicated training in digital screening for radiographers and screening radiologists is therefore recommended. Referral rates decrease and stabilise (learning curve effect) at a higher level than in conventional screening, yet with significantly enhanced cancer detection.