Women's attitudes and perspectives on the use of artificial intelligence in the assessment of screening mammograms.

PURPOSE: To investigate attitudes and perspectives on the use of artificial intelligence (AI) in the assessment of screening mammograms among women invited to BreastScreen Norway. METHOD: An anonymous survey was sent to all women invited to BreastScreen Norway during the study period, October 10, 2022, to December 25, 2022 (n = 84,543). Questions were answered on a 10-point Likert scale and as multiple-choice, addressing knowledge of AI, willingness to participate in AI studies, information needs, confidence in AI results and AI assisted reading strategies, and thoughts on concerns and benefits of AI in mammography screening. Analyses were performed using χ2 and logistic regression tests. RESULTS: General knowledge of AI was reported as extensive by 11.0% of the 8,355 respondents. Respondents were willing to participate in studies using AI either for decision support (64.0%) or triaging (54.9%). Being informed about use of AI-assisted image assessment was considered important, and a reading strategy of AI in combination with one radiologist preferred. Having extensive knowledge of AI was associated with willingness to participate in AI studies (decision support; odds ratio [OR]: 5.1, 95% confidence interval [CI]: 4.1-6.4, and triaging; OR: 3.4, 95% CI: 2.8-4.0) and trust in AI's independent assessment (OR: 6.8, 95% CI: 5.7, 8.3). CONCLUSIONS: Women invited to BreastScreen Norway had a positive attitude towards the use of AI in image assessment, given that human readers are still involved. Targeted information and increased public knowledge of AI could help achieve high participation in AI studies and successful implementation of AI in mammography screening.

Early screening outcomes before, during, and after a randomized controlled trial with digital breast tomosynthesis.

PURPOSE: To describe and compare early screening outcomes before, during and after a randomized controlled trial with digital breast tomosynthesis (DBT) including synthetic 2D mammography versus standard digital mammography (DM) (To-Be 1) and a follow-up cohort study using DBT (To-Be 2). METHODS: Retrospective results of 125,020 screening examinations from four consecutive screening rounds performed in 2014-2021 were described and compared for pre-To-Be 1 (DM), To-Be 1 (DM or DBT), To-Be 2 (DBT), and post-To-Be 2 (DM) cohorts. Descriptive analyses of rates of recall, biopsy, screen-detected and interval cancer, distribution of histopathologic tumor characteristics and time spent on image interpretation and consensus were presented for the four rounds including five cohorts, one cohort in each screening round except for the To-Be 1 trail, which included a DBT and a DM cohort. Odds ratios (OR) with 95% CIs was calculated for recall and cancer detection rates. RESULTS: Rate of screen-detected cancer was 0.90% for women screened with DBT in To-Be 2 and 0.64% for DM in pre-To-Be 1. The rates did not differ for the To-Be 1 DM (0.61%), To-Be 1 DBT (0.66%) and post-To-Be 2 DM (0.67%) cohorts. The interval cancer rates ranged between 0.13% and 0.20%. The distribution of histopathologic tumor characteristics did not differ between the cohorts. CONCLUSIONS: Screening all women with DBT following a randomized controlled trial in an organized, population-based screening program showed a temporary increase in the rate of screen-detected cancer.

Costs and Effects of Implementing Digital Tomosynthesis in a Population-Based Breast Cancer Screening Program: Predictions Using Results from the To-Be Trial in Norway.

BACKGROUND: Although several studies from Europe and the US have shown promising screening results favoring digital breast tomosynthesis compared with standard digital mammography (DM), both costs and effects of implementing tomosynthesis in routine screening programs remain uncertain. The cost effectiveness of using tomosynthesis in routine screening is debated in the literature, and model inputs from randomized trials are lacking. Using parameters mainly from a randomized controlled trial (the To-Be trial), we simulated costs and effects of implementing tomosynthesis in the national screening program BreastScreen Norway. METHODS: The To-Be trial was performed in Bergen from 2016 to 2017 within BreastScreen Norway, where females were randomized to either digital breast tomosynthesis including synthetic mammograms (DBT) or DM. The trial was followed by a cohort study offering all females DBT in 2018-2019. The trial included over 37,000 females, and allowed for estimation of short-term costs and effects related to screening, recall examinations and cancer detection. Using these and recent Norwegian estimates for 10-year stage-specific survival and treatment costs, the cost effectiveness of replacing DM with DBT in BreastScreen Norway was simulated in a decision tree model with probabilistic sensitivity analyses. Outcomes included false-positive screening results, screen-detected and interval cancers, stage at diagnosis, all-cause deaths, life-years gained, costs at recall and treatment and incremental cost-effectiveness ratio. RESULTS: The estimated additional cost of DBT was €8.10. Simulating ten rounds of screening from 2018 and 10-year survival and costs, 500 deaths were averted and 2300 life-years gained at an additional screening cost of €29 million for females screened with DBT versus DM. Taking over-diagnosis, recall and treatment costs into account, DBT was dominant in the deterministic analysis. The incremental cost-effectiveness ratio indicated cost savings of €1400 per life-year gained. Probabilistic sensitivity analyses showed that DBT was cost effective in over 50% of the simulations at all willingness-to-pay levels per life-year gained, and in 80% of the simulations at levels above €22,000. If willingness-to-pay levels up to €35,000 were assumed, DBT would be cost effective in over 50% of the simulations for additional costs of DBT of up to €32, almost four times the estimated additional cost of €8.10. CONCLUSION: DBT may be cost effective if implemented in BreastScreen Norway. However, generalizability of results could depend on factors varying between countries, such as recall rates, program sensitivity and specificity, treatment cost and willingness-to-pay levels.

Detection and significance of small and low proliferation breast cancer.

OBJECTIVES: To determine the frequency and discuss possible implications of early breast cancer with particularly good prognosis and defined by tumor diameter and cell proliferation. SETTING: Detection of small and slowly growing tumors presents a challenge in breast cancer management, due to the risk of over-treatment. Here, we attempted to define a group of such tumors by combining small diameter (≤10 mm, T1ab tumors) with low tumor cell proliferation (≤10% Ki67 expression rate). These tumors were termed small low proliferation cancers (SLPC). METHODS: Two population-based cohorts were studied: a small research series (n = 534), and a nation-wide registry-based series of prospectively collected routine data (n = 8433). In the latter, we stratified by detection mode; screen-detected, interval, and breast cancers detected outside of screening. Patients were treated according to national guidelines at time of their diagnosis. For both cohorts, we compared tumor histopathology and risk of breast cancer death using a log-rank test for cases with SLPC versus non-SLPC. RESULTS: In the research series (median follow-up 151 months), the frequency of SLPC was 10% (54/534), with one breast cancer death compared with 78 among the remaining 480 cases of non-SLPC (p = 0.008). In the registry series (median follow-up 42 months), the frequency of SLPC was 10% (854/8433), with five deaths compared to 187 among the remaining 7579 cases (p = 0.0004). CONCLUSIONS: SLPC was associated with very low risk of breast cancer death. Prospective randomized trials are needed to clarify whether less aggressive treatment could be a safe option for women with such early breast cancers.

Interval and Subsequent Round Breast Cancer in a Randomized Controlled Trial Comparing Digital Breast Tomosynthesis and Digital Mammography Screening.

Background Prevalent digital breast tomosynthesis (DBT) has shown higher cancer detection rates and lower recall rates compared with those of digital mammography (DM). However, data are limited on rates and histopathologic tumor characteristics of interval and subsequent round screen-detected cancers for DBT. Purpose To follow women randomized to screening with DBT or DM and to investigate rates and tumor characteristics of interval and subsequent round screen-detected cancers. Materials and Methods To-Be is a randomized controlled trial comparing the outcome of DBT and DM in organized breast cancer screening. The trial included 28 749 women, with 22 306 women returning for subsequent DBT screening 2 years later (11 201 and 11 105 originally screened with DBT and DM, respectively). Differences in rates, means, and distribution of histopathologic tumor characteristics between women prevalently screened with DBT versus DM were evaluated with Z tests, t tests, and χ2 tests. Relative risk (RR) with 95% CIs was calculated for the cancer rates. Results Interval cancer rates were 1.4 per 1000 screens (20 of 14 380; 95% CI: 0.9, 2.1) for DBT versus 2.0 per 1000 screens (29 of 14 369; 95% CI: 1.4, 2.9; P = .20) for DM. The rates of subsequent round screen-detected cancer were 8.1 per 1000 (95% CI: 6.6, 10.0) for women originally screened with DBT and 9.1 per 1000 (95% CI: 7.4, 11.0; P = .43) for women screened with DM. The distribution of tumor characteristics did not differ between groups for either interval or subsequent screen-detected cancer. The RR of interval cancer was 0.69 (95% CI: 0.39, 1.22; P = .20) for DBT versus DM, whereas RR of subsequent screen-detected cancer for women prevalently screened with DBT versus DM was 0.89 (95% CI: 0.67, 1.19; P = .43). Conclusion Rates of interval or subsequent round screen-detected cancers and their tumor characteristics did not differ between women originally screened with digital breast tomosynthesis (DBT) versus digital mammography. The analysis suggests that the benefits of prevalent DBT screening did not come at the expense of worse downstream screening performance measures in a population-based screening program. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Taourel in this issue.

Digital breast tomosynthesis in a population based mammographic screening program: Breast compression and early performance measures.

PURPOSE: We aimed to determine if compression force or pressure could be associated with early performance measures for women screened with digital breast tomosynthesis (DBT) in BreastScreen Norway. Early performance measures included rates of consensus, recall, and screen-detected breast cancer. METHOD: Data on compression force and pressure, compressed breast thickness and breast characteristics were extracted from an automated software for density assessment of DBT screening examinations for 25,286 women. For descriptive analyses, force (Newton, N) and pressure (kilopascal, kPa) were categorized into quartiles. Analyses were stratified by mammographic view, craniocaudal (CC) and mediolateral oblique (MLO). Logistic regression with restricted cubic splines was used to investigate the association between force and pressure as continuous exposures and early performance measures adjusted for age, compressed breast thickness and fibroglandular volume. RESULTS: Mean age of the screened women was 60.7 (SD = 5.2) years. Mean compression force was 90.8 (SD = 14.2) N for CC and 106.3 (SD = 20.6) N for MLO, and pressure was 11.3 (SD = 3.6) kPa for CC and 8.7 (SD = 2.0) kPa for MLO. The highest rates of screen-detected cancer were observed for low force (1.04 % for <82.5 N for CC and 1.07 % for <92.0 N for MLO) and low pressure (1.07 % for <7.2 kPa for MLO). No association was found between force or pressure as continuous exposures and early performance measures in adjusted regression analyses. CONCLUSIONS: We found the highest rates of screen-detected cancer for low force and pressure, but no significant association between continuous values of force or pressure and early performance measures in DBT. The findings might indicate that the levels of force and pressure in DBT are of lower significance for screening performance than reported in standard digital mammography.

Assessment of breast positioning criteria in mammographic screening: Agreement between artificial intelligence software and radiographers.

OBJECTIVES: To determine the agreement between artificial intelligence software (AI) and radiographers in assessing breast positioning criteria for mammograms from standard digital mammography and digital breast tomosynthesis. METHODS: Assessment of breast positioning was performed by AI and by four radiographers in pairs of two on 156 examinations of women screened in Bergen, April to September 2019, as part of BreastScreen Norway. Ten criteria were used; three for craniocaudal and seven for mediolateral-oblique view. The criteria evaluated the appearance of the nipple, breast rotation, pectoral muscle, inframammary fold and pectoral nipple line. Intraclass correlation and Cohen's kappa coefficient (κ) were used to investigate the correlation and agreement between the radiographer's assessments and AI. RESULTS: The intraclass correlation for the pectoral nipple line between the radiographers and AI was >0.92. A substantial to almost perfect agreement (κ > 0.69) was observed between the radiographers and AI on the nipple in profile criterion. We observed a slight to moderate agreement for the other criteria (κ = 0.06-0.52) and generally a higher agreement between the two pairs of radiographers (mean κ = 0.70) than between the radiographers and AI (mean κ = 0.41). CONCLUSIONS: AI has great potential in evaluating breast position criteria in mammography by reducing subjectivity. However, varying agreement between radiographers and AI was observed. Standardized and evidence-based criteria for definitions, understandings and assessment methods are needed to reach optimal image quality in mammography.

Visualization of the Nipple in Profile: Does It Really Affect Selected Outcomes in Organized Mammographic Screening?

OBJECTIVE: To investigate whether having the nipple imaged in profile was associated with breast characteristics or compression parameters, and whether it affected selected outcomes in screening with standard digital mammography or digital breast tomosynthesis. METHODS: In this IRB-approved retrospective study, results from 87 450 examinations (174 900 breasts) performed as part of BreastScreen Norway, 2016-2019, were compared by nipple in profile status and screening technique using descriptive statistics and generalized estimating equations. Unadjusted and adjusted odds ratios with 95% confidence intervals (95% CIs) were estimated for outcomes of interest, including age, breast volume, volumetric breast density, and compression force as covariates. RESULTS: Achieving the nipple in profile versus not in profile was associated with lower breast volume (845.1 cm3 versus 1059.9 cm3, P < 0.01) and higher mammographic density (5.6% versus 4.4%, P < 0.01). Lower compression force and higher compression pressure were applied to breasts with the nipple in profile (106.6 N and 11.5 kPa) compared to the nipple not in profile (110.8 N and 10.5 kPa, P < 0.01 for both). The adjusted odds ratio was 0.95 (95% CI: 0.88-1.02; P = 0.15) for recall and 0.92 (95% CI: 0.77-1.10; P = 0.36) for screen-detected cancer for nipple in profile versus not in profile. CONCLUSION: Breast characteristics and compression parameters might hamper imaging of the nipple in profile. However, whether the nipple was in profile or not on the screening mammograms did not influence the odds of recall or screen-detected cancer, regardless of screening technique.

Self-reported Pain Associated With Screening With Digital Breast Tomosynthesis.

OBJECTIVE: We aimed to investigate self-reported pain during screening with digital breast tomosynthesis (DBT). METHODS: The study was approved by the Regional Committee for Medical and Health Research Ethics in the South East of Norway (2015/424). Women completed a questionnaire about experienced pain directly after the examination, August-November 2019. A numeric rating scale (NRS, 0-10) was used. Data on compression force (N), pressure (kPa), and compressed breast thickness (mm) were obtained from the Digital Imaging and Communication in Medicine header and density assessment software. Stepwise ordinary least-squares regression was used to estimate mean self-reported pain score with 95% confidence interval (CI) for values of compression force, pressure, and compressed breast thickness. RESULTS: The mean pain score was 1.9, whereof 19.3% (822/4266) of the women reported moderate or severe pain. The mean pain score of 2.6 (95% CI: 2.4-2.7) was observed at a compression force of 60 N, decreasing to 1.3 (95% CI: 1.2-1.4) at 130 N. The mean pain score of 1.3 (95% CI: 1.1-1.4) was at a compression pressure of 6 kPa, increasing to 2.9 (95% CI: 2.7-3.1) at 16 kPa. The mean pain score was 0.6 (95% CI: 0.4-0.6) at a compressed breast thickness of 20 mm, increasing to 2.9 (95% CI: 2.7-3.1) at 90 mm. CONCLUSION: The mean pain score was low, 1.9 on NRS, for women screened with DBT. A compression force of 60-130 N and a pressure 6-16 kPa were associated with no or mild pain.

Screening at stationary versus mobile units in BreastScreen Norway.

Objective: To compare breast characteristics, compression parameters, and early performance measures (rates of recall, screen-detected and interval breast cancer, and histopathologic tumour characteristics) for mammographic screening at a stationary versus mobile screening unit. Methods: Results from 92,408 mammographic screening examinations performed as part of BreastScreen Norway during 2008­2017 at either a stationary (n = 52,620) or mobile (n = 39,788) unit in Hordaland county were compared using descriptive statistics and generalized estimating equations. A generalized estimating equation for a binary outcome was used to estimate crude and adjusted odds ratios with 95% confidence intervals for the outcomes of interest. Adjusted generalized estimating equation models included age, breast volume, and density grade as covariates. Results: Screening at the stationary unit was performed on smaller breasts with higher mammographic density, using lower compression force but higher pressure than at the mobile unit. Using the stationary screening unit as reference, for women screened at the mobile unit, the adjusted odds ratio was: for recall 0.94 (95% CI: 0.87--1.01), screen-detected breast cancer 0.92 (95% CI: 0.78--1.10), and interval breast cancer 1.17 (95% CI: 0.83­1.64). Conclusions: The quality of care did not differ for women screened at the stationary versus the mobile unit, but there were differences between the women who attended the two units. Sociodemographic factors should be included in future analyses to fully understand the risk of breast cancer among women residing in urban versus rural areas.

Interval and Consecutive Round Breast Cancer after Digital Breast Tomosynthesis and Synthetic 2D Mammography versus Standard 2D Digital Mammography in BreastScreen Norway.

Background Screening that includes digital breast tomosynthesis (DBT) with two-dimensional (2D) synthetic mammography (SM) or standard 2D digital mammography (DM) results in detection of more breast cancers than does screening with DM alone. A decrease in interval breast cancer rates is anticipated but is not reported. Purpose To compare rates and characteristics of (a) interval breast cancer in women screened with DBT and SM versus those screened with DM alone and (b) screen-detected breast cancer at consecutive screenings with DM. Materials and Methods This prospective cohort study from BreastScreen Norway included women screened with DBT and SM (study group) or DM alone (control group) between February 2014 and December 2015 (baseline). All women, except nonattendees, women with breast cancer, and those who exceeded the upper age limit, were consecutively screened with DM after 2 years. Interval breast cancer, sensitivity, and specificity were estimated for women screened at baseline. Recall, screen-detected breast cancer, and positive predictive value were analyzed for consecutively screened women. A χ2 test, t test (P < .001 after Bonferroni correction indicated a significant difference), and binomial regression model were used to analyze differences across groups. Results A total of 92 404 women who underwent baseline screening (mean age, 59 years ± 6 [standard deviation]) were evaluated; 34 641 women in the study group (mean age, 59 years ± 6) were screened with DBT and SM and 57 763 women in the control group (mean age, 59 years ± 6) were screened with DM. A total of 26 474 women in the study group (mean age, 60 years ± 5) and 45 543 women in the control group (mean age, 60 years ± 5) were consecutively screened with DM. Rates of interval breast cancer were 2.0 per 1000 screened women in the study group and 1.5 per 1000 screened women in the control group (P = .12). No differences in histopathologic characteristics of interval breast cancer were observed. In the consecutive screening round, rates of screen-detected breast cancer were 3.9 per 1000 screened women (study group) and 5.6 per 1000 screened women (control group) (P = .001). Rates of histologic grade 1 invasive cancer were 0.5 per 1000 screened women (study group) and 1.3 per 1000 screened women (control group) (P = .001). Conclusion No differences in interval breast cancer rates or tumor characteristics were observed in women screened with DBT and SM compared with women screened with DM. Higher rates of low-grade screen-detected tumors were observed in the control group at consecutive screening. © RSNA, 2019 Online supplemental material is available for this article.

Cost differences between digital tomosynthesis and standard digital mammography in a breast cancer screening programme: results from the To-Be trial in Norway.

BACKGROUND: Several studies in Europe and the US have shown promising results favouring digital breast tomosynthesis compared to standard digital mammography (DM). However, the costs of implementing the technology in screening programmes are not yet known. METHODS: A randomised controlled trial comparing the results from digital breast tomosynthesis including synthetic mammograms (DBT) vs. DM was performed in Bergen during 2016 and 2017 as a part of BreastScreen Norway. The trial included 29,453 women and allowed for a detailed comparison of procedure use and screening, recall and treatment costs estimated at the individual level. RESULTS: The increased cost of equipment, examination and reading time with DBT vs. DM was €8.5 per screened woman (95% CI 8.4-8.6). Costs of DBT remained significantly higher after adding recall assessment costs, €6.2 (95% CI 4.6-7.9). Substantial reductions in either examination and reading times, price of DBT equipment or price of IT storage and connectivity did not change the conclusion. Adding treatment costs resulted in too wide confidence intervals to draw definitive conclusions (additional costs of tomosynthesis €9.8, 95% CI -56 to 74). Performing biopsy at recall, radiation therapy and chemotherapy was significantly more frequent among women screened with DBT. CONCLUSION: The results showed lower incremental costs of DBT vs. DM, compared to what is found in previous cost analyses of DBT and DM. However, the incremental costs were still higher for DBT compared with DM after including recall costs. Further studies with long-term treatment data are needed to understand the complete costs of implementing DBT in screening.

Screening outcome for consecutive examinations with digital breast tomosynthesis versus standard digital mammography in a population-based screening program.

OBJECTIVES: To retrospectively investigate early performance measures of digital breast tomosynthesis (DBT) versus standard digital mammography (DM) for consecutive screening rounds. METHODS: We included information about 35,736 women screened in BreastScreen Norway, 2008-2016, with at least two consecutive screening examinations. The pair of two consecutive screening examinations was the unit of analysis, and results from the subsequent examination were the measure of interest. Screening technique changed during the study period, resulting in four study groups: DM after DM, DBT after DM, DM after DBT, and DBT after DBT. We compared selected early performance measures between the study groups. RESULTS: Recall for DM after DM was 3.6% and lower for all other study groups (p < 0.001). The rate of screen-detected breast cancer was 4.6/1000 for DM after DM; for DBT after DM and DBT after DBT, it was 9.9/1000 and 8.3/1000, respectively (p < 0.001 relative to DM after DM), and for DM after DBT 4.3/1000. The rate of tubular carcinoma was higher for DBT after DBT or after DM compared with DM after DM (p < 0.01). The rate of histologic grade 1 tumors was higher for DBT after DM compared with DM after DM (p < 0.001). We did not observe any statistical difference in the interval cancer rates. CONCLUSIONS: Lower recall and higher cancer detection rates for screening with DBT were sustainable over two consecutive screening rounds. Positive predictive values were higher for DBT than DM. There were no differences in the interval cancer rates between the study groups. KEY POINTS: • There is limited knowledge about early performance measures for screening with digital breast tomosynthesis beyond one screening round. • A decline in recall rate and an incline in the rate of screen-detected breast cancer were observed for women screened with DBT compared with DM, irrespective of prior screening technique. The interval breast cancer rate did not differ statistically for women screened with DBT versus DM. • Tumor characteristics tended to be prognostic favorable for DBT compared with DM with no differences in rates of more advanced cancers. The clinical significance of increased cancer detection and the potential for future mortality reduction remain unknown.

Two-view digital breast tomosynthesis versus digital mammography in a population-based breast cancer screening programme (To-Be): a randomised, controlled trial.

BACKGROUND: Digital breast tomosynthesis is an advancement of mammography, and has the potential to overcome limitations of standard digital mammography. This study aimed to compare first-generation digital breast tomo-synthesis including two-dimensional (2D) synthetic mammograms versus digital mammography in a population-based screening programme. METHODS: BreastScreen Norway offers all women aged 50-69 years two-view (craniocaudal and mediolateral oblique) mammographic screening every 2 years and does independent double reading with consensus. We asked all 32 976 women who attended the programme in Bergen in 2016-17, to participate in this randomised, controlled trial with a parallel group design. A study-specific software was developed to allocate women to either digital breast tomosynthesis or digital mammography using a 1:1 simple randomisation method based on participants' unique national identity numbers. The interviewing radiographer did the randomisation by entering the number into the software. Randomisation was done after consent and was therefore concealed from both the women and the radiographer at the time of consent; the algorithm was not disclosed to radiographers during the recruitment period. All data needed for analyses were complete 12 months after the recruitment period ended. The primary outcome measure was screen-detected breast cancer, stratified by screening technique (ie, digital breast tomosynthesis and digital mammography). A log-binomial regression model was used to estimate the efficacy of digital breast tomosynthesis versus digital mammography, defined as the crude risk ratios (RRs) with 95% CIs for screen-detected breast cancer for women screened during the recruitment period. A per-protocol approach was used in the analyses. This trial is registered at ClinicalTrials.gov, number NCT02835625, and is closed to accrual. FINDINGS: Between, Jan 14, 2016, and Dec 31, 2017, 44 266 women were invited to the screening programme in Bergen, and 32 976 (74·5%) attended. After excluding women with breast implants and women who did not consent to participate, 29 453 (89·3%) were eligible for electronic randomisation. 14 734 women were allocated to digital breast tomosynthesis and 14 719 to digital mammography. After randomisation, women with a previous breast cancer were excluded (digital breast tomosynthesis group n=314, digital mammography group n=316), women with metastases from melanoma (digital breast tomosynthesis group n=1), and women who informed the radiographer about breast symptoms after providing consent (digital breast tomosynthesis group n=39, digital mammography group n=34). After exclusions, information from 28 749 women were included in the analyses (digital breast tomosynthesis group n=14 380, digital mammography group n=14 369). The proportion of screen-detected breast cancer among the screened women did not differ between the two groups (95 [0·66%, 0·53-0·79] of 14 380 vs 87 [0·61%, 0·48-0·73] of 14 369; RR 1·09, 95% CI 0·82-1·46; p=0·56). INTERPRETATION: This study indicated that digital breast tomosynthesis including synthetic 2D mammograms was not significantly different from standard digital mammography as a screening tool for the detection of breast cancer in a population-based screening programme. Economic analyses and follow-up studies on interval and consecutive round screen-detected breast cancers are needed to better understand the effect of digital breast tomosynthesis in population-based breast cancer screening. FUNDING: Cancer Registry of Norway, Department of Radiology at Haukeland University Hospital, University of Oslo, and Research Council of Norway.

A randomized controlled trial of digital breast tomosynthesis versus digital mammography in population-based screening in Bergen: interim analysis of performance indicators from the To-Be trial.

OBJECTIVES: To describe a randomized controlled trial (RCT) of digital breast tomosynthesis including synthesized two-dimensional mammograms (DBT) versus digital mammography (DM) in a population-based screening program for breast cancer and to compare selected secondary screening outcomes for the two techniques. METHODS: This RCT, performed in Bergen as part of BreastScreen Norway, was approved by the Regional Committees for Medical Health Research Ethics. All screening attendees in Bergen were invited to participate, of which 89% (14,274/15,976) concented during the first year, and were randomized to DBT (n = 7155) or DM (n = 7119). Secondary screening outcomes were stratified by mammographic density and compared using two-sample t-tests, chi-square tests, ANOVA, negative binomial regression and tests of proportions (z tests). RESULTS: Mean reading time was 1 min 11 s for DBT and 41 s for DM (p < 0.01). Mean time spent at consensus was 3 min 12 s for DBT and 2 min 12 s for DM (p < 0.01), while the rate of cases discussed at consensus was 6.4% and 7.4%, respectively for DBT and DM (p = 0.03). The recall rate was 3.0% for DBT and 3.6% for DM (p = 0.03). For women with non-dense breasts, recall rate was 2.2% for DBT versus 3.4% for DM (p = 0.04). The rate did not differ for women with dense breasts (3.6% for both). Mean glandular dose per examination was 2.96 mGy for DBT and 2.95 mGy for DM (p = 0.433). CONCLUSIONS: Interim analysis of a screening RCT showed that DBT took longer to read than DM, but had significantly lower recall rate than DM. We found no differences in radiation dose between the two techniques. KEY POINTS: • In this RCT, DBT was associated with longer interpretation time than DM • Recall rates were lower for DBT than for DM • Mean glandular radiation dose did not differ between DBT and DM.

Digital Breast Tomosynthesis and Synthetic 2D Mammography versus Digital Mammography: Evaluation in a Population-based Screening Program.

Purpose To compare the performance of digital breast tomosynthesis (DBT) and two-dimensional synthetic mammography (SM) with that of digital mammography (DM) in a population-based mammographic screening program. Materials and Methods In this prospective cohort study, data from 37 185 women screened with DBT and SM and from 61 742 women screened with DM as part of a population-based screening program in 2014 and 2015 were included. Early performance measures, including recall rate due to abnormal mammographic findings, rate of screen-detected breast cancer, positive predictive value of recall, positive predictive value of needle biopsy, histopathologic type, tumor size, tumor grade, lymph node involvement, hormonal status, Ki-67 level, and human epidermal growth factor receptor 2 status were compared in women who underwent DBT and SM screening and in those who underwent DM screening by using χ2 tests, two-sample unpaired t tests, and tests of proportions. Results Recall rates were 3.4% for DBT and SM screening and 3.3% for DM screening (P = .563). DBT and SM screening showed a significantly higher rate of screen-detected cancer compared with DM screening (9.4 vs 6.1 cancers per 1000 patients screened, respectively; P < .001). The rate of detection of tumors 10 mm or smaller was 3.2 per 1000 patients screened with DBT and SM and 1.8 per 1000 patients screened with DM (P < .001), and the rate of grade 1 tumors was 3.3 per 1000 patients screened with DBT and SM versus 1.4 per 1000 patients screened with DM (P < .001). On the basis of immunohistochemical analyses, rates of lymph node involvement and tumor subtypes did not differ between women who underwent DBT and SM screening and those who underwent DM screening. Conclusion DBT and SM screening increased the detection rate of histologically favorable tumors compared with that attained with DM screening. © RSNA, 2018 Online supplemental material is available for this article.

The impact of compression force and pressure at prevalent screening on subsequent re-attendance in a national screening program.

Adherence to screening may indirectly help assess whether a prior screening examination deters women from returning for a subsequent examination. We investigated whether compression force and pressure in mammography were associated with re-attendance among prevalently screened women in the organized breast cancer screening program in Norway. Data on compression force (kg) and pressure (kPa) from women's first screening examination in the program (prevalent screening) and subsequent re-attendance were available for 31,225 women aged 50-68, screened during 2007-2013. Crude re-attendance rates and log-binomial regression models estimating the prevalence ratio of re-attendance were used to identify the association between compression force or pressure and re-attendance two-years later. Age and year at prevalent screening, county of residence, screening result (negative or false positive), breast volume, and breast density were included in analyses. Overall, 27,197 (87.1%) women re-attended the program. Re-attendance was highest for women who received a compression force of 10.0-13.9 kg (87.5%) or pressure of 9.0-17.9 kPa (87.8%) and lowest for those who received a compression force of <10.0 kg (85.0%) or pressure of <9.0 kPa (84.7%). The adjusted prevalence of re-attendance was 3% lower for women who received low compression force (<10.0 kg) and 2% lower for women who received low compression pressure (<9.0 kPa) relative to the reference groups (10.0-13.9 kg and 9.0-17.9 kPa, respectively). Future research related to re-attendance should also include information about women's experience of pain, anxiety and stress, as well as image quality.

Mode of detection: an independent prognostic factor for women with breast cancer.

OBJECTIVES: To investigate breast cancer survival and risk of breast cancer death by detection mode (screen-detected, interval, and detected outside the screening programme), adjusting for prognostic and predictive tumour characteristics. METHODS: Information about detection mode, prognostic (age, tumour size, histologic grade, lymph node status) and predictive factors (molecular subtypes based on immunohistochemical analyses of hormone receptor status (estrogen and progesterone) and Her2 status) were available for 8344 women in Norway aged 50-69 at diagnosis of breast cancer, 2005-2011. A total of 255 breast cancer deaths were registered by the end of 2011. Kaplan-Meier method was used to estimate six years breast cancer specific survival and Cox proportional hazard model to estimate hazard ratio (HR) for breast cancer death by detection mode, adjusting for prognostic and predictive factors. RESULTS: Women with screen-detected cancer had favourable prognostic and predictive tumour characteristics compared with interval cancers and those detected outside the screening programme. The favourable characteristics were present for screen-detected cancers, also within the subtypes. Adjusted HR of dying from breast cancer was two times higher for women with symptomatic breast cancer (interval or outside the screening), using screen-detected tumours as the reference. CONCLUSIONS: Detection mode is an independent prognostic factor for women diagnosed with breast cancer. Information on detection mode might be relevant for patient management to avoid overtreatment.