To evaluate the extent and histopathological characteristics of asymptomatic breast cancer detected outside the Norwegian Breast Cancer Screening Program (NBCSP) in women targeted by the programme.
Our study included 568 primary breast cancers (523 invasive and 45 ductal carcinoma in situ) diagnosed in 553 women aged 50-70, residing in Møre og Romsdal County, 2002-2008. The cancers were divided into screening-detected cancers in the NBCSP, interval cancers (ICs) and cancers detected in women not participating in the NBCSP (never participated and lapsed attendees), and further into asymptomatic and symptomatic cancers. Nottingham Prognostic Index (NPI) was used for comparisons across the groups and the distributions were compared using chi-square tests for statistical significance.
Twenty percent (19/97) of the ICs and 32% (69/213) of the breast cancers in non-participants were asymptomatic, with opportunistic screening as the most frequent detection method (42%, 8/19 for ICs and 54%, 37/69 for non-participants). There were no differences in distribution of NPI prognostic categories across subgroups of asymptomatic invasive cancers (screening-detected cancers in the NBCSP, asymptomatic ICs and asymptomatic cancers in non-participants) or between subgroups of symptomatic invasive cancers (symptomatic ICs and symptomatic cancers in non-participants). Asymptomatic cancers had a significantly more favourable distribution of NPI prognostic categories compared with symptomatic cancers (P
BACKGROUND A high rate of attendance among women invited to the Norwegian Breast Cancer Screening Programme (NBCSP) is essential to achieve optimal effect, including reduction in breast cancer mortality. This article describes attendance in the programme by county, period and women's age at invitation.MATERIAL AND METHOD All women in the age group 50?-?69 years who are registered in the National Population Register are invited to attend the NBCSP every second year. In the study period 2007?-?2014, 2 142 369 invitations were sent, and 1 600 293 screening examinations were performed for 710 169 women. Use of the data is pursuant to the Cancer Registry Regulations.RESULTS Altogether 84 % of the women invited attended at least once in the study period. The average attendance rate per screening round was 75 %. In Rogaland, Nordland and Sogn og Fjordane counties more than 80 % attended, while in Oslo the figure was 62 %. The highest rate of attendance recorded was for women in the age group 62?-?67 years. The attendance in the prior screening round was of influence for reattendance.INTERPRETATION The mammography screening programme has a high level of acceptance among women in the target group. Possible reasons for the variation in attendance among the county districts should be identified.
To compute a ratio between the estimated numbers of lives saved from breast cancer death and the number of women diagnosed with a breast cancer that never would have been diagnosed during the woman's lifetime had she not attended screening (epidemiologic over-diagnosis) in the Norwegian Breast Cancer Screening Program.
The Norwegian Breast Cancer Screening Program invites women aged 50-69 to biennial mammographic screening. Results from published studies using individual level data from the programme for estimating breast cancer mortality and epidemiologic over-diagnosis comprised the basis for the ratio. The mortality reduction varied from 36.8% to 43% among screened women, while estimates on epidemiologic over-diagnosis ranged from 7% to 19.6%. We computed the average estimates for both values. The benefit-detriment ratio, number of lives saved, and number of women over-diagnosed were computed for different scenarios of reduction in breast cancer mortality and epidemiologic over-diagnosis.
For every 10,000 biennially screened women, followed until age 79, we estimated that 53-61 (average 57) women were saved from breast cancer death, and 45-126 (average 82) were over-diagnosed. The benefit-detriment ratio using average estimates was 1:1.4, indicating that the programme saved about one life per 1-2 women with epidemiologic over-diagnosis.
The benefit-detriment ratio estimates of the Norwegian Breast Cancer Screening Program, expressed as lives saved from breast cancer death and epidemiologic over-diagnosis, should be interpreted with care due to substantial uncertainties in the estimates, and the differences in the scale of values of the events compared.
Objective Fluctuations in the incidence of breast cancer in Norway in the last three decades are partly explained by the use of hormone replacement therapy and mammography screening, but overdiagnosis has also been suggested as a cause. We assessed the trends in breast cancer incidence and overdiagnosis in Norway. Methods We calibrated our microsimulation model to Norwegian Cancer Registration data. The model takes into account the use of mammography (both within and outside the Norwegian Breast Cancer Screening Programme) and of hormone replacement therapy. We obtained a proper fit of breast cancer incidence in recent years, when assuming an increase in the background risk for breast cancer, and estimated overdiagnosis. Results We estimated a 2% overdiagnosis rate as a fraction of all cancers diagnosed in women aged 50-100, and a 3% overdiagnosis rate as a fraction of all cancers diagnosed in women aged 50-70 (i.e. screening age). If all of the increased incidence would be the result of the detection of slow growing tumours, these estimates were 7% and 11%, respectively. Conclusion Besides mammography and hormone replacement therapy use, additional risk factors contributed to the sudden increase in breast cancer incidence in Norway. Overdiagnosis estimates due to screening were within the range of international plausible estimates.
The Norwegian Breast Cancer Screening Program started in 1996. To the authors' knowledge, this is the first report using individual-based data on invitation and participation to analyze breast cancer mortality among screened and nonscreened women in the program.
Information on dates of invitation, attendance, breast cancer diagnosis, emigration, death, and cause of death was linked by using unique 11-digit personal identification numbers assigned all inhabitants of Norway at birth or immigration. In total, 699,628 women ages 50 to 69 years without prior a diagnosis of breast cancer were invited to the program from 1996 to 2009 and were followed for breast cancer through 2009 and death through 2010. Incidence-based breast cancer mortality rate ratios (MRRs) were compared between the screened and nonscreened cohorts using a Poisson regression model. The MRRs were adjusted for calendar period, attained age, years since inclusion in the cohorts, and self-selection bias.
The crude breast cancer mortality rate was 20.7 per 100,000 women-years for the screened cohort compared with 39.7 per 100,000 women-years for the nonscreened cohort, resulting in an MRR of 0.52 (95% confidence interval, 0.47-0.59). The mortality reduction associated with attendance in the program was 43% (MRR, 0.57; 95% confidence interval, 0.51-0.64) after adjusting for calendar period, attained age, years after inclusion in the cohort, and self-selection bias.
After 15 years of follow-up, a 43% reduction in mortality was observed among women who attended the national mammographic screening program in Norway.
Mammographic density (MD) is one of the strongest known breast cancer risk factors. Twin studies have suggested that a large part of the variation in MD is genetically determined. We hypothesized that breast cancer susceptibility variants may affect MD, and that their effects may be modified by nongenetic factors.
We assessed MD, using a computer-assisted method, on 2,348 postmenopausal Caucasian women (50-69 years) who participated in the Norwegian Breast Cancer Screening Program (NBCSP) in 2004 or 2006-07. We used linear regression (additive models) to determine the association between each SNP and MD, adjusting for age, body mass index (BMI), and study. We evaluated MD associations with 17 established breast cancer SNPs, overall, and by strata defined by non-genetic factors.
Two variants, 6q25.1-rs9383938 and TXNRD2-rs8141691, were statistically significantly associated with percent MD (P = 0.019 and 0.03, respectively), with the 6q25.1-rs9383938 association being consistent with the SNP effect on breast cancer risk. The effect of 6q25.1-rs3734805 on percent MD varied between parous and nulliparous women (Pinteraction = 0.02), whereas the effects of 9q31.2-rs865686 and MRPS30:FGF10-rs4415084 differed across strata of BMI (Pinteraction = 0.01 and 0.005, respectively). There was no evidence of effect modification by estrogen and progestin therapy use or alcohol consumption.
This study provides novel evidence of shared genetic risk factors between MD and breast cancer and of possible MD genetic-environmental interactions.
Although the results may be chance findings, they nevertheless highlight the need to investigate interactions with nongenetic factors in studies on the genetics of MD.
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.
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.
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
To investigate possible associations between breast compression parameters, including compression force, pressure and compressed breast thickness, and mammographic density assessed by an automated software.
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 (?) 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.
A fair negative correlation was observed between compression pressure and absolute dense volume (? = - 0.37 for CC and ? = - 0.34 for MLO). A moderate negative correlation was identified for compressed breast thickness and percentage dense volume (? = - 0.56 for CC and ? = - 0.62 for MLO). These correlations were corroborated by the corresponding associations obtained in the adjusted regression analyses.
Results from this study indicate that breast compression parameters may influence absolute and percentage dense volume measured by the automated software.
• 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 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.
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.
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.
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.