Breast density and outcome of mammography screening: a cohort study.

The purpose of this study was to investigate the effect of breast density on breast cancer (BC) mortality in a mammography screening programme. The cohort included 48 052 women participating in mammography screening in Copenhagen, Denmark, where biennial screening is offered to women aged 50-69 years. We collected information for the years 1991-2001 on screening outcome, incident BCs (screen-, interval-, and later detected), and BC deaths. Breast density was dichotomised into fatty (F) and mixed/dense (M/D) breasts. Screening sensitivity was measured as the odds ratio of interval versus screen-detected cancer for dense versus F breasts. Poisson regression was used to estimate the ratios for BC incidence, case fatality, and mortality between women with M/D and F breasts. For women with M/D breasts, the odds ratio of an interval cancer was 1.62 (95% confidence interval, CI, 1.14-2.30), and the age-adjusted rate ratios were 2.45 (95% CI 2.14-2.81) for BC incidence, 0.60 (95% CI 0.43-0.84) for case fatality, and 1.78 (95% CI 1.17-2.72) for BC mortality. The study shows that BC in women with M/D breasts is more frequent, but on average less severe, than in women with F breasts.

Cancer mortality in the United Kingdom: projections to the year 2025.

The purpose of this study was to project mortality rates in the United Kingdom for the period 2006-2025 for 21 major cancers on the basis of the observed trends in mortality rates during 1971-2005, and to estimate the implication in terms of expected deaths. Age-period-cohort models were applied to official statistics. The projected decrease in age-standardised mortality rates for all cancers from 2003 to 2023 was 17% in men and 16% in women. Future mortality rates were projected to decline for most cancer sites. In men, there were small projected increases in mortality rates from cancers of the oral cavity, oesophagus and melanoma, with a larger projected increase (14% over 20 years) in mortality of liver cancer. In women, the only projected increase (18%) was for corpus uteri. The numbers of deaths will increase for most cancers, with a 30% increase in all cancers projected for men and a 12% increase projected for women. Mortality rates from cancer as a whole have been falling in the United Kingdom since 1990, and this decline was projected to continue into the future as well as the declining rates in both sexes for most cancers. Actual numbers of deaths will increase for most cancers.

Complexities in the estimation of overdiagnosis in breast cancer screening.

There is interest in estimating and attributing temporal changes in incidence of breast cancer in relation to the initiation of screening programmes, in particular to estimation of overdiagnosis of breast cancer as a result of screening. In this paper, we show how screening introduces complexities of analysis and interpretation of incidence data. For example, lead time brings forward time- and age-related increases in incidence. In addition, risk factors such as hormone replacement therapy use have been changing contemporaneously with the introduction of screening. Although we do not indicate exactly how such complexities should be corrected for, we use some simple informal adjustments to show how they may account for a substantial proportion of increased incidence, which might otherwise erroneously have been attributed to overdiagnosis. We illustrate this using an example of analysis of breast cancer incidence data from Sweden.

Predicting the impact of the screening programme for colorectal cancer in the UK.

OBJECTIVES: Screening for colorectal cancer by biennial testing for faecal occult blood is being introduced in the UK from 2007. We examine the likely impact of the programme, in terms of reduced mortality, lives saved and changes in incidence, over the next 20 years. SETTING: Projections of incidence and mortality of colorectal cancer in England, and the policy that has been adopted for screening in England (biennial at ages 60-69 from 2007, then 60-74 in 2010). METHODS: The results are based on the output of a simulation model that has been used to examine cost-effectiveness of screening policy options, with two scenarios regarding compliance with screening; both assume that 20% of the population will never attend for screening, but attendance of those who do is modelled either as a random 60% or 80%, at each screening round. RESULTS: The decrease in mortality rates expected 20 years after introducing screening is 13-17% in men and 12-15% in women (depending on the attendance levels). The model predicts an initial rise in incidence, followed (after six to seven years) by a fall, so that there is little net change in the number of cases detected over a 20-year period. CONCLUSION: Percentage changes in mortality seem modest, but the projected saving in terms of numbers of lives is not negligible--1800-2400 per year by 2025 in England (equivalent numbers are 2200-2700 in all over the UK). Newer screening modalities may improve on these projected results.

Comparison of early performance indicators for screening projects within the European Breast Cancer Network: 1989-2000.

In 1989 the European Breast Cancer Network (EBCN) was established by the first pilot projects for breast cancer screening, co-funded by the Europe Against Cancer programme. We report early performance indicators for these EBCN projects while taking into account their organizational setting. Out of 17 projects in the network, 10 projects from six European countries contributed aggregated data on number of invitations, screening examinations, and breast cancers detected over the period 1989-2000. Results were summarized separately for projects in centralized versus decentralized health care environments. The European Guidelines for quality assurance in mammography screening provided reference values for the performance indicators. The most prominent finding in this study was the higher participation rate in centralized versus decentralized projects (average participation in 1998: 74 versus 33%; P<0.001), whereas the invitation system and screening policy in these projects were similar. Detection rates and characteristics of cancers detected at initial and subsequent screening examinations showed no significant differences between centralized and decentralized projects. Even though early performance indicators for centralized versus decentralized projects were similar, the impact of breast screening on mortality from this disease at the population level will differ since the decentralized projects reach only part of the target population.

Tumour size distribution in mammography screening.

Many mammography screening programmes have not been able to show higher percentages of small invasive cancers detected at subsequent screens than at initial screens. This has been a matter of serious concern as it contradicts the very theory of screening. Based on data from the county of Fyn, Denmark we evaluated the distribution based on point estimates, as well as on the entire tumour size distribution. The programme changed the amount of tumours less than 15 or 20 mm, but did not change the amount of tumours less than 10 mm. We evaluated the entire tumour size distribution and found that screen number was the only significant factor, implying that the number of screens changed the tumour size distribution. We recommend that the entire tumour size distribution is used to evaluate the ability of a programme to detect small breast cancers, instead of only point estimates as has previously been the practice.

Reporting of performance indicators of mammography screening in Europe.

We compared short-term indicators for service mammography screening in Europe. Data were available from 17 programmes, although not all programmes provided a comprehensive reporting. More than 90% of the target population had been screened within the last 3 years in the WE trial, whereas only two-thirds of women in England and Copenhagen had been screened within the last 3 years, which will delay or reduce the effect of screening compared with the trial. Participation was highest in sparsely populated areas. Detection rates at first screen reached three times the baseline in Copenhagen, the Netherlands and North-West England. The clinical characteristics of screen-detected cases were badly reported. Given their importance for the long-term effect of screening, further data are warranted. Sensitivity and specificity could be measured only indirectly; they showed, however, considerable variation between programmes. Fyn, Florence and Stockholm had succeeded in combining high specificity with high sensitivity. With different recall policies, different proportions of women will experience a false-positive test; expected numbers after three screens were 14%, 10% and 1%, for England, Copenhagen and the Netherlands, respectively. Based on the observed wide variation in short-term indicators, a similar wide variation is expected in the effect of screening on breast cancer mortality.

Early outcome of mammography screening in Copenhagen 1991-99.

OBJECTIVES: To evaluate the early outcome of an organised mammography screening programme in an area with little opportunistic screening. SETTING: The municipality of Copenhagen, Denmark, during four invitation rounds 1991-99. METHODS: The following outcome measures were used: rates of participation, recall, false positive, and cancer detection. Benign biopsy, distribution of tumour size, lymph node status, and malignancy grade. RESULTS: A total of 106,933 screens were undertaken, and 824 invasive breast carcinomas or CIS were detected. The detection rate was 11.9 per 1000 participants in the first invitation round, and it continued to be high in subsequent rounds. The percentage of CIS cases was 11%. Coverage declined from 71% in the first round to 62% in the fourth, although 91% of those participating in the previous three rounds attended. The programme operated with a high recall rate. The false positive rate was also high, being 5.6% at first screen, and 1.8% later on. However, 90% of false positives were sorted out already at assessment. The percentage of screen detected invasive breast cancers with a tumour diameter < or = 10 mm was 39% compared with 16% of all invasive breast cancers in these age groups in Copenhagen before screening. CONCLUSION: Copenhagen is an area with a high incidence of breast cancer and with relatively little opportunistic screening. The start of a screening programme with a high recall rate in this area resulted in a detection rate above 1%. The Copenhagen programme met or exceeded most of the interim measures recommended in the European Guidelines.

Modelling the likely effect of the increase of the upper age limit from 70 to 73 for breast screening in the UK National Programme.

The UK National Breast Screening Programme is planned to have the age range for invitation to screening expanded from 50-70 to 47-73. At the upper limit, this represents one additional screen taking place in the early 70s. We aimed to estimate the likely effect of this on breast cancer mortality and on overdiagnosis of breast cancer. We used estimates of breast cancer incidence and survival by detection mode (screening or symptomatic), screening lead time and mortality from competing causes to estimate the likely numbers of breast cancer deaths prevented per 1000 women screened, using both a stochastic continuous time model and a semi-deterministic discrete time model. In the continuous model, we estimated that per 1000 women screened 1.2 deaths would be prevented and in the discrete model 0.91 deaths. In the latter model, we also estimated that there would be around 6.8 years of life saved per 1000 women screened and an additional two diagnoses of breast cancer. These results suggest that the expansion of the upper age limit will be cost-effective. They remain to be confirmed by evaluation of the age extension. They provide prior estimates that may inform the evaluation of the age extension.

Misleading presentation of breast cancer in popular magazines.

CONTEXT: Women commonly misunderstand their risk for breast cancer, overestimating both their risk for developing the disease at a young age and their lifetime risk. OBJECTIVE: To determine whether age bias occurs in popular media coverage of breast cancer. SELECTION STRATEGY: The search term breast cancer was used to identify 389 articles in U.S. magazines with a circulation of at least 500,000 published between January 1, 1993, and June 30, 1997. MAIN OUTCOME MEASURES: Presence of age-related themes and age of patients with breast cancer who were described in vignettes. RESULTS: Age-related themes included breast cancer as a cause of premature death, breast cancer in mothers of young children, and the impact of a breast cancer diagnosis on dating and marriage. Factual information about age as a risk factor for breast cancer was presented in only 14% of articles, and age was often included in vignettes describing a woman with breast cancer. Thirty-four percent of the articles included one or more breast cancer vignettes. These articles included 172 unique vignettes in which patient age was described. In 84% of the vignettes (144 of 172), women were diagnosed with breast cancer before 50 years of age; in 47% (80 of 172), women were diagnosed before 40 years of age. On the basis of the age-specific incidence of breast cancer in the United States, the expected percentages would be 16% and 3.6%, respectively. CONCLUSIONS: Stories about breast cancer in popular U.S. magazines misrepresent the age distribution of the disease, emphasizing atypical cases of early-onset breast cancer and their social consequences. This presentation of breast cancer may contribute to women's fears of breast cancer and to overestimates of personal risk.

Breast cancer incidence after the start of mammography screening in Denmark.

Mammography screening may lead to overdiagnosis of asymptomatic breast cancers, that would otherwise not have given rise to clinical symptoms. This aspect was studied in three regional screening programmes in Denmark, which started in Copenhagen municipality, Fyn county, and Frederiksberg municipality in 1991, 1993, and 1994, respectively. In these regions, we compared time trends in incidence of invasive breast cancer with the rest of Denmark. Since the number of clinical mammograms was relatively low, it was reasonable to assume that the breast cancer incidence outside the three screening regions represented the incidence of a population with low-intensity opportunistic screening. In Copenhagen and Fyn, a prevalence peak in incidence was seen during the first invitation round. During the subsequent invitation rounds, the incidence dropped to a level in line with the incidence expected without screening. The pattern was different in the small municipality of Frederiksberg, where the sensitivity was low during the first invitation round. Inclusion of screen-detected ductal carcinoma in situ cases did not change these results. The experiences from Copenhagen and Fyn show that organised mammography screening can operate without overdiagnosis of breast cancer.