Women's conceptual knowledge about breast cancer screening and overdiagnosis in Norway: a cross-sectional study.

OBJECTIVE: To investigate conceptual knowledge about mammographic screening among Norwegian women. DESIGN: We administered a cross-sectional, web-based survey. We used multiple-choice questions and a grading rubric published by a research group from Australia. SETTING: Our Norwegian-language survey was open from April to June 2020 and targeted women aged 45-74 years. PARTICIPANTS: 2033 women completed our questionnaire. We excluded 13 women outside the target age range and 128 women with incomplete data. Responses from 1892 women were included in the final study sample. PRIMARY AND SECONDARY OUTCOME MEASURES: The questionnaire focused on women's knowledge about the breast cancer mortality reduction, false positive results and overdiagnosis associated with mammographic screening. The primary outcome was the mean number of marks assigned in each of the three themes and overall. There were three potential marks for questions about breast cancer mortality, one for false positives and six for overdiagnosis. RESULTS: Most women (91.7%) correctly reported that screened women are less likely to die of breast cancer than non-screened women. 39.7% of women reported having heard of a 'false positive screening result' and 86.2% identified the term's definition; 51.3% of women had heard of 'overdiagnosis' and 14.8% identified the term's definition. The mean score was 2.59 of 3 for questions about breast cancer mortality benefit and 0.93 of 1 for the question about false positive screening results. It was 2.23 of 6 for questions about overdiagnosis. CONCLUSIONS: Most participants correctly answered questions about the breast cancer mortality benefit and false positive results associated with screening. The proportion of correct responses to questions about overdiagnosis was modest, indicating that conceptual knowledge about overdiagnosis was lower. Qualitative studies that can obtain in-depth information about women's understanding of overdiagnosis may help improve Norwegian-language information about this challenging topic.

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.

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.

Breast compression across consecutive examinations among females participating in BreastScreen Norway.

OBJECTIVE::  Breast compression is used in mammography to improve image quality and reduce radiation dose. However, optimal values for compression force are not known, and studies have found large variation in use of compression forces between breast centres and radiographers. We investigated breast compression parameters, including compression force, compression pressure and compressed breast thickness across four consecutive full field digital mammography screening examinations for 25,143 subsequently screened females aged 50-69 years. METHODS:: Information from females attending four consecutive screening examinations at two breast centres in BreastScreen Norway during January 2007 - March 2016 was available. We compared the changes in compression force, compression pressure and compressed breast thickness from the first to fourth consecutive screening examination, stratified by craniocaudal (CC) and mediolateral oblique (MLO) view. RESULTS:: Compression force, compression pressure and compressed breast thickness increased relatively by 18.3, 14.4 and 8.4% respectively, from first to fourth consecutive screening examination in CC view (p<0.001 for all). For MLO view, the values increased relatively by 12.3% for compression force, 9.9% for compression pressure and 6.9% for compressed breast thickness from first to fourth consecutive screening examination (p<0.001 for all). CONCLUSION:: We observed increasing values of breast compression parameters across consecutive screening examinations. Further research should investigate the effect of this variation on image quality and females' experiences of discomfort and pain. ADVANCES IN KNOWLEDGE:: Breast compression force, compression pressure and compressed breast thickness increased across consecutive screening examinations, which might be of influence for the females' experiences of discomfort and pain during the examination and for image quality.

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.

Comparison of subjective and fully automated methods for measuring mammographic density.

Background Breast radiologists of the Norwegian Breast Cancer Screening Program subjectively classified mammographic density using a three-point scale between 1996 and 2012 and changed into the fourth edition of the BI-RADS classification since 2013. In 2015, an automated volumetric breast density assessment software was installed at two screening units. Purpose To compare volumetric breast density measurements from the automated method with two subjective methods: the three-point scale and the BI-RADS density classification. Material and Methods Information on subjective and automated density assessment was obtained from screening examinations of 3635 women recalled for further assessment due to positive screening mammography between 2007 and 2015. The score of the three-point scale (I = fatty; II = medium dense; III = dense) was available for 2310 women. The BI-RADS density score was provided for 1325 women. Mean volumetric breast density was estimated for each category of the subjective classifications. The automated software assigned volumetric breast density to four categories. The agreement between BI-RADS and volumetric breast density categories was assessed using weighted kappa (kw). Results Mean volumetric breast density was 4.5%, 7.5%, and 13.4% for categories I, II, and III of the three-point scale, respectively, and 4.4%, 7.5%, 9.9%, and 13.9% for the BI-RADS density categories, respectively ( P for trend < 0.001 for both subjective classifications). The agreement between BI-RADS and volumetric breast density categories was kw = 0.5 (95% CI = 0.47-0.53; P < 0.001). Conclusion Mean values of volumetric breast density increased with increasing density category of the subjective classifications. The agreement between BI-RADS and volumetric breast density categories was moderate.

Breast compression parameters and mammographic density in the Norwegian Breast Cancer Screening Programme.

OBJECTIVES: To investigate possible associations between breast compression parameters, including compression force, pressure and compressed breast thickness, and mammographic density assessed by an automated software. METHODS: We obtained data on breast compression parameters, breast volume, absolute and percentage dense volume, and body mass index for 14,698 women screened with two-view (craniocaudal, CC, and mediolateral oblique, MLO) digital mammography, in the Norwegian Breast Cancer Screening Programme, 2014-2015. The Spearman correlation coefficient (ρ) was used to measure correlation between breast compression parameters, breast volume and absolute and percentage dense volume. Linear regression was used to examine associations between breast compression parameters and absolute and percentage dense volume, adjusting for breast volume, age and BMI. RESULTS: A fair negative correlation was observed between compression pressure and absolute dense volume (ρ = - 0.37 for CC and ρ = - 0.34 for MLO). A moderate negative correlation was identified for compressed breast thickness and percentage dense volume (ρ = - 0.56 for CC and ρ = - 0.62 for MLO). These correlations were corroborated by the corresponding associations obtained in the adjusted regression analyses. CONCLUSIONS: Results from this study indicate that breast compression parameters may influence absolute and percentage dense volume measured by the automated software. KEY POINTS: • A fair correlation was identified between compression pressure and absolute dense volume • A moderate correlation was identified between compressed breast thickness and percentage dense volume • Breast compression may influence automated density estimates.

Compression force and radiation dose in the Norwegian Breast Cancer Screening Program.

PURPOSE: Compression force is used in mammography to reduce breast thickness and by that decrease radiation dose and improve image quality. There are no evidence-based recommendations regarding the optimal compression force. We analyzed compression force and radiation dose between screening centers in the Norwegian Breast Cancer Screening Program (NBCSP), as a first step towards establishing evidence-based recommendations for compression force. MATERIALS AND METHODS: The study included information from 17 951 randomly selected screening examinations among women screened with equipment from four different venors at fourteen breast centers in the NBCSP, January-March 2014. We analyzed the applied compression force and radiation dose used on craniocaudal (CC) and mediolateral-oblique (MLO) view on left breast, by breast centers and vendors. RESULTS: Mean compression force used in the screening program was 116N (CC: 108N, MLO: 125N). The maximum difference in mean compression force between the centers was 63N for CC and 57N for MLO. Mean radiation dose for each image was 1.09mGy (CC: 1.04mGy, MLO: 1.14mGy), varying from 0.55mGy to 1.31mGy between the centers. Compression force alone had a negligible impact on radiation dose (r2=0.8%, p=<0.001). CONCLUSION: We observed substantial variations in mean compression forces between the breast centers. Breast characteristics and differences in automated exposure control between vendors might explain the low association between compression force and radiation dose. Further knowledge about different automated exposure controls and the impact of compression force on dose and image quality is needed to establish individualised and evidence-based recommendations for compression force.

Compression forces used in the Norwegian Breast Cancer Screening Program.

OBJECTIVE: Compression is used in mammography to reduce breast thickness, which is claimed to improve image quality and reduce radiation dose. In the Norwegian Breast Cancer Screening Program (NBCSP), the recommended range of compression force for full-field digital mammography (FFDM) is 11-18 kg (108-177 N). This is the first study to investigate the compression force used in the programme. METHODS: The study included information from 17,951 randomly selected females screened with FFDM at 14 breast centres in the NBCSP, during January-March 2014. We investigated the applied compression force on the left breast in craniocaudal and mediolateral oblique views for breast centres, mammography machines within the breast centres and for the radiographers. RESULTS: The mean compression force for all mammograms in the study was 116 N and ranged from 91 N to 147 N between the breast centres. The variation in compression force was wider between the breast centres than that between mammography machines (range 137-155 N) and radiographers (95-143 N) within one breast centre. Approximately 59% of the mammograms in the study complied with the recommended range of compression force. CONCLUSION: A wide variation in applied compression force was observed between the breast centres in the NBCSP. This variation indicates a need for evidence-based recommendations for compression force aimed at optimizing the image quality and individualizing breast compression. Advances in knowledge: There was a wide variation in applied compression force between the breast centres in the NBCSP. The variation was wider between the breast centres than that between mammography machines and radiographers within one breast centre.