Variation in the Effectiveness of Breast Screening by Year of Follow-Up (original) (raw)
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The Lancet, 2006
Background The effi cacy of screening by mammography has been shown in randomised controlled trials in women aged 50 years and older, but is less clear in younger women. A meta-analysis of all previous trials showed a 15% mortality reduction in invited women aged 40-49 years at study entry, but this fi nding could be due in part to screening of women after age 50 years. The Age trial was designed to study the eff ect on mortality of inviting women for annual mammography from age 40 years. Methods 160 921 women aged 39-41 years were randomly assigned in the ratio 1:2 to an intervention group of annual mammography to age 48 years or to a control group of usual medical care. The trial was undertaken in 23 NHS breast-screening units in England, Wales, and Scotland. The primary analysis was based on the intention-to-treat principle and compared mortality rates in the two groups at 10 years' follow-up. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN24647151. Findings At a mean follow-up of 10•7 years there was a reduction in breast-cancer mortality in the intervention group, in relative and absolute terms, which did not reach statistical signifi cance (relative risk 0•83 [95% CI 0•66-1•04], p=0•11; absolute risk reduction 0•40 per 1000 women invited to screening [95% CI-0•07 to 0•87]). Mortality reduction adjusted for non-compliance in women actually screened was estimated as 24% (RR 0•76, 95% CI 0•51-1•01). Interpretation Although the reduction in breast-cancer mortality observed in this trial is not signifi cant, it is consistent with results of other trials of mammography alone in this age-group. Future decisions on screening policy should be informed by further follow-up from this trial and should take account of possible costs and harms as well as benefi ts.
Repeated mammographic screening reduces breast cancer mortality along the continuum of age
Journal of Medical Screening, 2002
Objective: The optimal age boundaries for breast cancer screening are still under debate. A case-referent design was used to describe the effect of mammographic screening on breast cancer mortality along the continuum of age, based on a 20 year follow up period. Setting: The population based breast cancer screening programme in Nijmegen, The Netherlands, which has biennially invited women over 35 years since 1975. Methods: Cases, defined as women who died from primary breast cancer between 1987 and 1997, were selected from the group of women who received at least one invitation to the screening programme. For 157 cases, 785 women from the same group were selected as referents. Information on the index screening (the screening examination preceding diagnosis of the case) was collected for both cases and referents. The risk of dying from breast cancer was calculated per 10 year moving age group for women who had attended the index screening versus those who had not. Results: The youngest 10 year age group showing an effect in our study were women aged 45-54 at their index screening. Breast cancer mortality for women in this group who attended the index screening was 32% lower, although not significant, than for women who did not (odds ratio (OR) 0.68, 95% confidence interval (95% CI) 0.33 to 1.41). This reduction in risk was not explained solely by an effect in women over 50 because the OR in women aged 45-49 was 0.56 (95% CI 0.20 to 1.61). Reductions in mortality became smaller with increasing age. Nevertheless, for women over 60 at index screening, participation in screening over a maximum 4 year period before diagnosis of the case yielded protective effects at least up to an age around 80. Conclusions: Although our results are based on a relatively small number of cases, they suggest that even in a programme with a 2 year screening interval there may be a benefit of starting screening around age 45. Also older women who participate at least once every 4 years still have much to gain from screening. I n screening for breast cancer, among the issues still under debate are the optimal lower and upper age boundaries delineating the target population. 1-3 In younger women breast cancer is a relatively important cause of death, but the effect of mammographic screening is not clear cut. A National Institute of Health consensus development conference in 1997, focusing on women of 40-49, did not produce a unanimous statement on when to start mammographic screening. 4 Since then a new meta-analysis including the most recent follow up data on all eight randomised controlled trials showed for the first time a significant 18% reduction in mortality among women of 40-49 at entry into the trials. 5 Also accumulating evidence shows that mammographic screening in younger women meets levels of performance compared with performance in women 50 years and older, especially if programmes achieve high quality and screen at 12-18 month intervals. The impact of (continuing) screening by mammography at older ages has been studied to a lesser extent, but is likely to receive considerable attention in the next decade with a growing population of healthy elderly women. 2 6 To our knowledge, only three studies reported on the effect of screening women over 65. All indicated that the reduction in breast cancer mortality among women of 65-74 may be as large as 55%. 7-9 A model based study further reported that even under pessimistic assumptions, the balance between positive and negative effects of breast cancer screening remains favourable up to an age around 80. Commonly used cut off points for age specific effects of mammographic screening in previously published reports are arbitrary to some extent and have no direct biological justification. Therefore, one of the suggestions for future research of the National Institute of Health Consensus Development Panel was to examine the effects of mammography screening for all ages at risk, looking upon age as a continuum. 4 As shown by Smith, 3 comparing breast cancer screening among successive-for example, 10 year-age groups is also more relevant to public health policy because of the gradual increasing trend in the efficacy of screening as women age. In the population based programme in Nijmegen, introduced in 1975, screening was offered to women aged 35 and older over a 20 year period. This setting provides an opportunity to study the effect of attending screening over the whole age range of women invited.
JNCI Monographs
The purpose of this overview is to estimate more precisely the long-term effect of mammography screening by adding four more years of follow-up to women aged 40-49 years in the four Swedish trials on mammography screening. Data from the four trials were merged and linked to the Swedish Cancer and Cause of Death Register for 1958-1993 and 1951-1993 respectively to identify date of breast cancer diagnosis and cause and date of death. The invited and control groups comprised 48,569 and 40,247 women respectively. At the December 1993 follow-up, 602 and 482 breast cancer cases were identified in the two groups respectively, of which 104 and 111 had breast cancer as the underlying cause of death. This corresponds to a relative risk (RR) of 0.77 (95% CI: 0.59-1.01) for the two groups. In the 40-44 age group at randomization, 94% of breast cancer patients in the study and 89% in the control group were diagnosed before the age of 50; however, among breast cancer deaths in this age group, only two in the invited and five in the control group died after age 50. At follow-up of women 40-44 years at randomization 208 women in the invited and 184 in the control group were reported to the Cancer registry with breast cancer. Out of these 195 (94%) and 163 (89%) respectively were reported before the age of 50. Further, the relative risk for the age group 40-44 years at randomization by age at follow-up was 1.11, 0.51 and 0.46 for the age groups 45-49, 50-54, and 55-59 at follow-up. This study shows a 23% reduction in the breast cancer mortality in women 40-49 years at randomization achieved from a median trial time of 7.0 years, a median follow-up time of 12.8 years, and a screening interval of 18-24 months. Almost all of the effect in the 40-44 year age group at randomization was due to screening before the age of 50.
American Journal of Roentgenology, 2013
B reast cancer is the second most common cancer among American women [1], and multiple studies have shown that screening mammography reduces breast cancer mortality for women over 40 years old [2, 3]. For example, in one of the longest running studies to date, the Swedish Two-County Trial [4], has shown a 30% risk reduction in breast cancer mortality over a follow-up period of nearly 3 decades. Other studies have shown that women in their 40s with breast carcinoma who undergo regular screening mammography have a more favorable cancer stage at diagnosis than those who do not undergo regular screening; however, critics argue that downstaging represents overdiagnosis of ductal carcinoma in situ (DCIS) and nonaggressive cancers that might not impact survival [5]. Between 1990 and 2007, breast cancer deaths decreased 3.2% per year among women younger than 50 years and
Health Technology Assessment, 2020
Background There remains disagreement on the long-term effect of mammographic screening in women aged 40–49 years. Objectives The long-term follow-up of a randomised controlled trial that offered annual mammography to women aged 40–49 years. The estimation of the effect of these mammograms on breast cancer and other-cause mortality, and the effect on incidence, with implications for overdiagnosis. Design An individually randomised controlled trial comparing offering annual mammography with offering usual care in those aged 40–48 years, and thus evaluating the effect of annual screening entirely taking place before the age of 50 years. There was follow-up for an average of 23 years for breast cancer incidence, breast cancer death and death from other causes. We analysed the mortality and incidence data by Poisson regression and estimated overdiagnosis formally using Markov process models. Setting Twenty-three screening units in England, Wales and Scotland within the NHS Breast Screen...
Clinical Breast Cancer, 2015
In this study we assessed the effect of a population screening program. A comparison was performed in the 50-to 69-year-old age group between 496 patients with breast cancer who participated on the screening program and 1325 who did not. The screened group showed significantly better results in all prognostic factors and in specific mortality than all nonscreened groups. Introduction: Screening programs for breast cancer aim to allow early diagnosis, and thus reduce mortality. The aim of this study was to assess the effect of a population screening program in a sample of women aged between 50 and 69 years in terms of recurrence, metastasis, biological profiles, and survival, and to compare their results with those of women of a wider age range who did not participate on the screening program. Patients and Methods: A prospective multicenter study in which 1821 patients with 1873 breast tumors who received surgery between 1999 and 2014 at MútuaTerrassa University Hospital and the Hospital of Terrassa in Barcelona were analyzed. A comparison was performed in the 50-to 69-year-old age group between those who participated on the screening program and those who did not. Results: The mean age of patients was 58 years. The mean follow-up was 72 months, and median follow-up 59 months. The screened group showed significantly better results in all prognostic factors and in specific mortality than all nonscreened groups. The specific mortality rate in the screened patients was 2.4% (12/496), local recurrence 2.8% (14/496), and metastasis at 10 years 3.6% (18/496). In the nonscreened group, younger women presented a higher rate of metastasis (16.4% [81/493]) and a shorter disease-free period (77.1% [380/493]). The age group older than 70 years had the highest number of T4 tumors (7.5% [30/403]) and the highest proportion of radical surgery (50.4% [203/403]). Conclusion: Patients in the screening program presented improved survival. We speculate that extending breast cancer screening programs to women younger than 50 and older than 70 years could bring about mortality benefits.
Breast Cancer Screening for Women at Average Risk
JAMA, 2015
IMPORTANCE Breast cancer is a leading cause of premature mortality among US women. Early detection has been shown to be associated with reduced breast cancer morbidity and mortality. OBJECTIVE To update the American Cancer Society (ACS) 2003 breast cancer screening guideline for women at average risk for breast cancer. PROCESS The ACS commissioned a systematic evidence review of the breast cancer screening literature to inform the update and a supplemental analysis of mammography registry data to address questions related to the screening interval. Formulation of recommendations was based on the quality of the evidence and judgment (incorporating values and preferences) about the balance of benefits and harms. EVIDENCE SYNTHESIS Screening mammography in women aged 40 to 69 years is associated with a reduction in breast cancer deaths across a range of study designs, and inferential evidence supports breast cancer screening for women 70 years and older who are in good health. Estimates of the cumulative lifetime risk of false-positive examination results are greater if screening begins at younger ages because of the greater number of mammograms, as well as the higher recall rate in younger women. The quality of the evidence for overdiagnosis is not sufficient to estimate a lifetime risk with confidence. Analysis examining the screening interval demonstrates more favorable tumor characteristics when premenopausal women are screened annually vs biennially. Evidence does not support routine clinical breast examination as a screening method for women at average risk. RECOMMENDATIONS The ACS recommends that women with an average risk of breast cancer should undergo regular screening mammography starting at age 45 years (strong recommendation). Women aged 45 to 54 years should be screened annually (qualified recommendation). Women 55 years and older should transition to biennial screening or have the opportunity to continue screening annually (qualified recommendation). Women should have the opportunity to begin annual screening between the ages of 40 and 44 years (qualified recommendation). Women should continue screening mammography as long as their overall health is good and they have a life expectancy of 10 years or longer (qualified recommendation). The ACS does not recommend clinical breast examination for breast cancer screening among average-risk women at any age (qualified recommendation). CONCLUSIONS AND RELEVANCE These updated ACS guidelines provide evidence-based recommendations for breast cancer screening for women at average risk of breast cancer. These recommendations should be considered by physicians and women in discussions about breast cancer screening.
2008
Objectives The objective of this study was to compare breast cancer outcomes among women subject to different policies on mammography screening frequency. Setting Data were obtained for women participating in the Screening Mammography Programme of British Columbia (SMPBC) for 1988 -2005. The SMPBC changed its policy for women aged 50 -79 years from annual to biennial mammography in 1997, but retained an annual recommendation for women aged 40 -49 years. Methods Breast cancer outcomes were compared for women participating in the programme before and after 1997 for two groups: ages 40 -49 and 50-79 years. Results There were data on 658,151 women. Comparing pre-1997 and post-1997, the median interscreen interval increased by 11.1 months in women 50 -79 but by only 0.3 months in women aged 40-49. Excluding those detected at initial screen, 6291 breast cancers were identified. Comparing pre-1997 and post-1997: the relative rates (RR) of screen detected cancer increased in women aged 40 -49 (RR ¼ 1.32) and the rate of invasive cancers !20 mm at diagnosis decreased (RR ¼ 0.83); the rate of cancers with axillary node involvement increased in women aged 50 -79 (RR ¼ 1.23). Cancer survival improved after 1997 for women diagnosed at ages 40 -49 (hazard ratio ¼ 0.62), but was unchanged for women aged 50-79. Breast cancer mortality rates did not change between the periods in either age group. Conclusion The proximal cancer outcomes considered (staging and survival) improved in women aged 40-49 but this was offset in women aged 50-79 associated with the change in screen frequency. These changes did not result in alterations in breast cancer mortality rates in either age group.