Why did the breast cancer lymph node status distribution improve in Denmark in the pre-mammography screening period of 1978-1994?

An exploration for quantification of overdiagnosis and its effect for breast cancer screening

Objective

To redefine overdiagnosis and reestimate the proportion of overdiagnosis of breast cancer caused by screening based on the Surveillance, Epidemiology, and End Results (SEER, 1973−2015) Program data.

Methods

The breast cancer diagnosed before 1977 was defined as the no-screening cohort since America had initiated breast cancer screening from 1977. The breast cancer diagnosed in 1999 was defined as the screening cohort due to no increases in both the proportion of early-stage breast cancer until 1999 and the overall survival of early-stage breast cancer diagnosed over the three years since 1999. The magnitude of overdiagnosis was calculated as the difference in the proportions of early-stage breast cancer patients with long-time (15-year) survival to all breast cancer patients between two cohorts.

Results

Over 23 years before and after widespread screening in America, the proportion of early-stage breast cancer patients increased from 52.1% (16,891/32,443) to 72.7% (16,021/22,025) (P<0.001). The 15-year survival rate of early-stage breast cancer patients increased from 51.1% to 61.5% (P<0.001), while the proportions of early-stage breast cancer patients with long-time survival to all breast cancer patients increased from 26.6% (52.1%×51.1%) to 44.7% (72.7%×61.5%). Assuming no improvements in cancer screening technology and treatment technology, 18.1% (44.7%−26.6%) of breast cancer patients were overdiagnosed associated with screening. The age-specific overdiagnosis rates were 18.9%, 24.7%, 24.5%, 20.5%, and 8.3% for breast cancer patients aged 40−49, 50−59, 60−69, 70−74, and ≥75 years old, respectively.

Conclusions

Overdiagnosis caused by mammographic screening is probably overestimated in current screening practices. Further trials with more sophisticated designs and analyses are needed to validate our findings in the future.

Retrospective cohort study of breast cancer incidence, health service use and outcomes in Europe: a study of feasibility

Background

Comparisons of outcomes of health care in different systems can be used to inform health policy. The EuroHOPE (European Healthcare Outcomes, Performance and Efficiency) project investigated the feasibility of comparing routine data on selected conditions including breast cancer across participating European countries.

Methods

Routine data on incidence, treatment and mortality by age and clinical characteristics for breast cancer in women over 24 years of age were obtained (for a calendar year) from linked hospital discharge records, cancer and death registers from Finland, the Turin metropolitan area, Scotland and Sweden (all 2005), Hungary (2006) and Norway (2009). Age-adjusted breast cancer incidence and 1-year survival were estimated for each country/region.

Results

In total, 24 576 invasive breast cancer cases were identified from cancer registries from over 13 million women. Age-adjusted incidence ranged from 151.1 (95%CI 147.2-155.0) in Hungary to 234.7 (95%CI 227.4-242.0)/100 000 in Scotland. One-year survival ranged from 94.1% (95%CI 93.5-94.7%) in Scotland to 97.1% (95%CI 96.2-98.1%) in Italy. Scotland had the highest proportions of poor prognostic factors in terms of tumour size, nodal status and metastases. Significant variations in data completeness for prognostic factors prevented adjustment for case mix.

Conclusion

Incidence of and survival from breast cancer showed large differences between countries. Substantial improvements in the use of internationally recognised common terminology, standardised data coding and data completeness for prognostic indicators are required before international comparisons of routine data can be used to inform health policy.

Outcome of breast cancer screening in Denmark

BACKGROUND

In Denmark, national roll-out of a population-based, screening mammography program took place in 2007-2010. We report on outcome of the first four biennial invitation rounds.

METHODS

Data on screening outcome were retrieved from the 2015 and 2016 national screening quality reports. We calculated coverage by examination; participation after invitation; detection-, interval cancer- and false-positive rates; cancer characteristics; sensitivity and specificity, for Denmark and for the five regions.

RESULTS

At the national level coverage by examination remained at 75-77%; lower in the Capital Region than in the rest of Denmrk. Detection rate was slightly below 1% at first screen, 0.6% at subsequent screens, and one region had some fluctuation over time. Ductal carcinoma in situ (DCIS) constituted 13-14% of screen-detected cancers. In subsequent rounds, 80% of screen-detected invasive cancers were node negative and 40% ≤10 mm. False-positive rate was around 2%; higher for North Denmark Region than for the rest of Denmark. Three out of 10 breast cancers in screened women were diagnosed as interval cancers.

CONCLUSIONS

High coverage by examination and low interval cancer rate are required for screening to decrease breast cancer mortality. Two pioneer local screening programs starting in the 1990s were followed by a decrease in breast cancer mortality of 22-25%. Coverage by examination and interval cancer rate of the national program were on the favorable side of values from the pioneer programs. It appears that the implementation of a national screening program in Denmark has been successful, though regional variations need further evaluation to assure optimization of the program.

Breast-Cancer Tumor Size, Overdiagnosis, and Mammography Screening Effectiveness

BACKGROUND

The goal of screening mammography is to detect small malignant tumors before they grow large enough to cause symptoms. Effective screening should therefore lead to the detection of a greater number of small tumors, followed by fewer large tumors over time.

METHODS

We used data from the Surveillance, Epidemiology, and End Results (SEER) program, 1975 through 2012, to calculate the tumor-size distribution and size-specific incidence of breast cancer among women 40 years of age or older. We then calculated the size-specific cancer case fatality rate for two time periods: a baseline period before the implementation of widespread screening mammography (1975 through 1979) and a period encompassing the most recent years for which 10 years of follow-up data were available (2000 through 2002).

RESULTS

After the advent of screening mammography, the proportion of detected breast tumors that were small (invasive tumors measuring <2 cm or in situ carcinomas) increased from 36% to 68%; the proportion of detected tumors that were large (invasive tumors measuring ≥2 cm) decreased from 64% to 32%. However, this trend was less the result of a substantial decrease in the incidence of large tumors (with 30 fewer cases of cancer observed per 100,000 women in the period after the advent of screening than in the period before screening) and more the result of a substantial increase in the detection of small tumors (with 162 more cases of cancer observed per 100,000 women). Assuming that the underlying disease burden was stable, only 30 of the 162 additional small tumors per 100,000 women that were diagnosed were expected to progress to become large, which implied that the remaining 132 cases of cancer per 100,000 women were overdiagnosed (i.e., cases of cancer were detected on screening that never would have led to clinical symptoms). The potential of screening to lower breast cancer mortality is reflected in the declining incidence of larger tumors. However, with respect to only these large tumors, the decline in the size-specific case fatality rate suggests that improved treatment was responsible for at least two thirds of the reduction in breast cancer mortality.

CONCLUSIONS

Although the rate of detection of large tumors fell after the introduction of screening mammography, the more favorable size distribution was primarily the result of the additional detection of small tumors. Women were more likely to have breast cancer that was overdiagnosed than to have earlier detection of a tumor that was destined to become large. The reduction in breast cancer mortality after the implementation of screening mammography was predominantly the result of improved systemic therapy.

Comparative analysis of breast cancer mortality following mammography screening in Denmark and Norway

BACKGROUND

Denmark and Norway are the best countries to study effects of mammography screening, because they are the only countries with stepwise introduction of nationwide mammography screening, enabling comparative effectiveness studies of high quality. Although Denmark and Norway are countries with similar populations and health care systems, reported reductions in breast cancer mortality (incidence-based) caused by screening differed vastly; 25% in Denmark versus 10% in Norway. This study explores reasons for this difference.

PATIENTS AND METHODS

We compared two published studies from the Danish and Norwegian screening programs (Olsen et al., 2005; Kalager et al., 2010) investigating biennial mammography screening for women age 50-69 years. Four comparison groups of women were constructed ('current' and 'historical screening groups'; 'current' and 'historical nonscreening groups') based on county of residence. We calculated incidence-based breast cancer mortality in the current versus the historical period for screening and nonscreening groups, using mortality rate ratios (MRR) in the two countries, accounting for concomitant changes in breast cancer mortality.

RESULTS

In the screening groups, similar reductions in breast cancer mortality were found when periods preceding and following start of screening were compared, in Denmark [25%; MRR 0.75; 95% confidence interval (CI) 0.64% to 0.88%] and in Norway (28%; MRR 0.72; 95% CI 0.63% to 0.81%). However, mortality increased in Denmark in the current nonscreening group compared with the historical nonscreening group; for women >59 years, breast cancer mortality increased by 14% (MRR 1.14, 95% CI 1.07-1.22), whereas in Norway a 19% reduction was seen (MRR 0.81, 95% CI 0.72-0.92). This increase accounts for the different relative effect of screening in Denmark and Norway; 25% breast cancer mortality reduction in Denmark, 10% in Norway.

CONCLUSIONS

The seemingly larger effect of screening in Denmark may not be solely attributable to screening itself, but to increased breast cancer mortality in women older than 59 years not invited to screening.

Patterns of nodal staging during breast conservation surgery in the medicare patient: will the ACOSOG Z0011 trial change the pattern of care?

ACOSOG Z0011 spares axillary dissection (AD) in breast conservation surgery (BCS) patients with T1/T2 tumors and 1-2 positive nodes. Current patterns of care and the impact of Z0011 on AD versus additional surgery rates for Medicare patients undergoing BCS are unknown. SEER data linked to Medicare claims for 1999-2005 were reviewed for women with invasive nonmetastatic breast cancer who underwent nodal staging on the same day as BCS. There were 3,280 women with T1/T2 tumors and positive nodes who underwent same-day nodal staging; 2,532 (77.2 %) of these women had 1-2 positive nodes. Assuming 25.7 % have extracapsular extension, 651 women would require AD. However, 1,881 women, or 57.4 % of those with T1/T2 tumors and positive nodes, would be spared AD. Meanwhile, among the 748 women having ≥ 3 positive nodes, 579 underwent same-day AD, but under Z0011, would now wait for permanent section. A total of 160 of these women underwent re-excision or completion mastectomy at a later date anyway, when delayed AD could be performed. The remaining 419 women with ≥ 3 positive nodes would require an additional surgery date for the sole purpose of completion AD. The Z0011 paradigm would consequently necessitate an additional surgery date for 1,070 (651 + 419) women, or 32.6 % of those with T1/T2 tumors and positive nodes. The Z0011 paradigm appears to increase the number of Medicare patients undergoing BCS who require an additional surgery date but decrease the number requiring AD to a greater extent. Future changes in the use of AD or axillary irradiation may yet modify that impact substantially.

Screening for breast cancer with mammography

BACKGROUND

A variety of estimates of the benefits and harms of mammographic screening for breast cancer have been published and national policies vary.

OBJECTIVES

To assess the effect of screening for breast cancer with mammography on mortality and morbidity.

SEARCH METHODS

We searched PubMed (22 November 2012) and the World Health Organization's International Clinical Trials Registry Platform (22 November 2012).

SELECTION CRITERIA

Randomised trials comparing mammographic screening with no mammographic screening.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Eight eligible trials were identified. We excluded a trial because the randomisation had failed to produce comparable groups.The eligible trials included 600,000 women in the analyses in the age range 39 to 74 years. Three trials with adequate randomisation did not show a statistically significant reduction in breast cancer mortality at 13 years (relative risk (RR) 0.90, 95% confidence interval (CI) 0.79 to 1.02); four trials with suboptimal randomisation showed a significant reduction in breast cancer mortality with an RR of 0.75 (95% CI 0.67 to 0.83). The RR for all seven trials combined was 0.81 (95% CI 0.74 to 0.87). We found that breast cancer mortality was an unreliable outcome that was biased in favour of screening, mainly because of differential misclassification of cause of death. The trials with adequate randomisation did not find an effect of screening on total cancer mortality, including breast cancer, after 10 years (RR 1.02, 95% CI 0.95 to 1.10) or on all-cause mortality after 13 years (RR 0.99, 95% CI 0.95 to 1.03).Total numbers of lumpectomies and mastectomies were significantly larger in the screened groups (RR 1.31, 95% CI 1.22 to 1.42), as were number of mastectomies (RR 1.20, 95% CI 1.08 to 1.32). The use of radiotherapy was similarly increased whereas there was no difference in the use of chemotherapy (data available in only two trials).

AUTHORS' CONCLUSIONS

If we assume that screening reduces breast cancer mortality by 15% and that overdiagnosis and overtreatment is at 30%, it means that for every 2000 women invited for screening throughout 10 years, one will avoid dying of breast cancer and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. Furthermore, more than 200 women will experience important psychological distress including anxiety and uncertainty for years because of false positive findings. To help ensure that the women are fully informed before they decide whether or not to attend screening, we have written an evidence-based leaflet for lay people that is available in several languages on www.cochrane.dk. Because of substantial advances in treatment and greater breast cancer awareness since the trials were carried out, it is likely that the absolute effect of screening today is smaller than in the trials. Recent observational studies show more overdiagnosis than in the trials and very little or no reduction in the incidence of advanced cancers with screening.

The breast screening programme and misinforming the public

The information provided to the public by the NHS Breast Screening Programme has been criticized for lack of balance, omission of information on harms and substantially exaggerated estimates of benefit. These shortcomings have been particularly evident in the various invitation leaflets for breast screening and in the Programme's own 2008 Annual Review, which celebrated 20 years of screening. The debate on screening has been heated after new data published in the last two years questioned the benefit and documented substantial harm. We therefore analysed whether the recent debate and new pivotal data about breast screening has had any impact on the contents of the new 2010 leaflet and on the 2010 Annual Review. We conclude that spokespeople for the Programme have stuck to the beliefs about benefit that prevailed 25 years ago. Concerns about over-diagnosis have not been addressed either and official documents still downplay this most important harm of breast cancer screening.

Why mammography screening has not lived up to expectations from the randomised trials

We analysed the relation between tumour sizes and stages and the reported effects on breast cancer mortality with and without screening in trials and observational studies. The average tumour sizes in all the trials suggest only a 12% reduction in breast cancer mortality, which agrees with the 10% reported in the most reliable trials. Recent studies of tumour sizes and tumour stages show that screening has not lowered the rate of advanced cancers. In agreement with this, recent observational studies of breast cancer mortality have failed to find an effect of screening. In contrast, screening leads to serious harms in healthy women through overdiagnosis with subsequent overtreatment and false-positive mammograms. We suggest that the rationale for breast screening be urgently reassessed by policy-makers. The observed decline in breast cancer mortality in many countries seems to be caused by improved adjuvant therapy and breast cancer awareness, not screening. We also believe it is more important to reduce the incidence of cancer than to detect it 'early.' Avoiding getting screening mammograms reduces the risk of becoming a breast cancer patient by one-third.

The impact of advances in treatment on the efficacy of mammography screening

OBJECTIVE

The objective of this commentary is to argue that advances in therapy are diminishing the efficacy of mammography screening.

METHOD

Key studies which demonstrate this effect are briefly reviewed.

RESULTS

The author argues that, for screening to be beneficial, the treatment of screen-detected cancers must be more effective than that of clinically-detected cancers. If there was no effective therapy for breast cancer, then screening would offer no benefit. Furthermore, as breast cancer treatments improve over time, both the absolute and relative benefits of screening will diminish. This is evident in the overview of the nine successive mammography screening trials, which have shown a decrease in the benefit of mammography screening over time, with the three most recent trials showing no benefit at all. Breast cancer adjuvant therapy was widely available in the three most recent mammography screening trials, but not the earlier trials. Additionally, population-based studies seem to suggest that the benefit of mammography screening is diminishing as treatments continue to improve.

CONCLUSION

Thus, in the years ahead, further declines in breast cancer mortality will likely be fueled by advances in therapy, and not by improvements in screening technology.