Screening for breast cancer in order to reduce the burden of breast cancer in Sri Lanka – the way forward – Is mammography an essential tool?
Yes, mammography is an essential tool for screening for breast cancer. To what extent mammography reduces the burden of breast cancer will depend on the context, country and the research. The NCCP guidelines published in 2014 gives a comprehensive detail in ‘Early Detection and Management of Breast Symptoms’. This is valid even today. [Ref]
Q1 Does mammography screening decrease the incidence or mortality rate from breast cancer?
N0, because mammography detects breast tumours in the asymptomatic phase. Therefore it does not have any effect on the incidence although it can detect cancers / tumours in the very early stages. Even the effect on mortality rates are minimal. The evidence is given below.
(Pap-smears detect changes in the cervix even earlier than the asymptomatic stage – the pre-cancerous stage. This is why pap-smears decrease the incidence of cervical cancers.)
1992 Canadian National Breast Screening Study – Breast cancer detection and death rates among women aged 40 to 49 years. [Ref 1992]
Objectives were to evaluate the efficacy of the combination of annual screening with mammography, physical examination of the breasts and the teaching of breast self-examination in reducing the rate of death from breast cancer among women aged 40 to 49 years on entry.
Conclusions were that the study was internally valid, and there was no evidence of randomization bias. Screening with yearly mammography and physical examination of the breasts detected considerably more node-negative, small tumours than usual care, but it had no impact on the rate of death from breast cancer up to 7 years’ follow-up from entry.
2001 Screening for breast cancer with mammography – Cochrane Review [Ref 2001]
Objectives were to assess the effect of screening for breast cancer with mammography on mortality and morbidity.
Conclusions were that currently available reliable evidence does not show a survival benefit of mass screening for breast cancer (and the evidence is inconclusive for breast cancer mortality). Women, clinicians and policy makers should consider these findings carefully when they decide whether or not to attend or support screening program.
2002 Breast cancer mortality after 11 to 16 years follow-up. A randomized screening trial of mammography in women age 40 to 49 years. [Ref – 2002]
Objectives were to compare breast cancer mortality in 40- to 49-year-old women who received either 1) screening with annual mammography, breast physical examination, and instruction on breast self-examination on 4 or 5 occasions or 2) community care after a single breast physical examination and instruction on breast self-examination.
Conclusions. After 11 to 16 years of follow-up, four or five annual screenings with mammography, breast physical examination, and breast self-examination had not reduced breast cancer mortality compared with usual community care after a single breast physical examination and instruction on breast self-examination. The study data show that true effects of 20% or greater are unlikely.
2013 Screening for breast cancer with Mammography Cochrane Review [Ref – 2013]
Objective To assess the effect of screening for breast cancer with mammography on mortality and morbidity.
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).
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.
2017 Effectiveness of and overdiagnosis from mammography screening in the Netherlands: population-based study [Ref – 2017]
Objective. To analyse stage specific incidence of breast cancer in the Netherlands where women have been invited to biennial mammography screening since 1989 (ages 50-69) and 1997 (ages 70-75), and to assess changes in breast cancer mortality and quantified overdiagnosis.
Conclusions. From 1989 to 2012, no significant decrease in the incidence of stage 2-4 breast cancers has been observed in women aged ≥50
Screening would be associated with 0 to 5% reductions in breast cancer mortality in women aged ≥50, whereas improved patient management would be associated with a 28% reduction.
In 2010-12 about one third of breast cancers among women invited to screening represented overdiagnosis.
2018 Mammography screening: A major issue in medicine. European Journal of Cancer [Ref – 2018]
- After 20–30 years of mammography screening, the incidence rates of advanced and metastatic breast cancer have remained stable.
- Breast cancer mortality rates have not decreased more rapidly in areas where mammography is in place since the late 1980s.
- One third to one half of mammography-detected breast cancers would not have been clinical during lifetime (overdiagnosis).
- Breast screening randomised trials have adopted distinctive methods that led to exaggerating the efficacy of screening.
- The influence mammography screening may have on mortality decreases with the increasing efficiency of cancer therapies.
- The comparison of the performance of different screening modalities – e.g. mammography, digital mammography, ultrasonography, magnetic resonance imaging(MRI), three-dimensional tomosynthesis (TDT) – concentrates on detection rates, which is the ability of a technique to detect more cancers than other techniques. However, a greater detection rate tells little about the capacity to prevent interval and advanced cancers and could just reflect additional overdiagnosis. Studies based on the incidence of advanced cancers and on the evaluation of overdiagnosis should be conducted before marketing new breast-imaging technologies.
2014 Evidence-based de-implementation for contradicted, unproven, and aspiring healthcare practices. [Ref – 2014]
Abandoning ineffective medical practices and mitigating the risks of untested practices are important for improving patient health and containing healthcare costs. Historically, this process has relied on the evidence base, societal values, cultural tensions, and political sway, but not necessarily in that order. We propose a conceptual framework to guide and prioritize this process, shifting emphasis toward the principles of evidence-based medicine, acknowledging that evidence may still be misinterpreted or distorted by recalcitrant proponents of entrenched practices and other biases
Q2 Is Sri Lanka facing a breast cancer epidemic? Probably YES. Epidemiologists will answer this correctly.
Does mammography by early detection and treatment solve this problem – definitely NO
Then, what may be the solutions? – Prevention NOT necessarily early detection.
Can we prevent Breast Cancer?
A 2014 review of primary prevention of breast cancer [Ref]. ‘Despite recent calls to intensify the search for new risk factors for breast cancer, acting on information that we already have could prevent thousands of cases each year. This article reviews breast cancer primary prevention strategies that are applicable to all women, discusses the underutilization of chemoprevention in high-risk women, highlights the additional advances that could be made by including young women in prevention efforts, and comments on how the molecular heterogeneity of breast cancer affects prevention research and strategies.’
Factors that can be changed are called modifiable factors. [Ref – Australian Government]
- Alcohol – drinking alcohol increases your risk for breast cancer. The more you drink, the greater the increase in risk. If you do drink alcohol, limit your alcohol intake to 1 standard drink a day.
- Body weight – keeping to a healthy weight range reduces risk of breast cancer. Aim to keep to a healthy body weight that is within a Body Mass Index (BMI) range of 18.5 to 25 kg/m2, and have a waist circumference of below 80 cm (31.5 in).
- Physical activity – active women of all ages are at reduced risk of breast cancer compared to women who do not exercise. Aim for at least 30 minutes of moderate-intensity physical activity every day. The more exercise you do, the bigger the benefits.
- Menopausal hormone therapy – using menopausal hormone therapy (MHT) that contains both an oestrogen and a progestogen is associated with an increased risk of breast cancer, with the risk increasing the longer you take it. If you are taking MHT, review your needs regularly with your doctor.
- Breastfeeding – breastfeeding can reduce risk of breast cancer – and the longer the duration of breastfeeding, the greater the benefits.
Q3 Considerable of cases can be missed through mammography alone. High quality mammography machines and ultrasound scans (especially in younger aged group) are needed for screening.
Does high quality mammography machine by early detection solve this problem? Again, NO
Age-adjusted breast cancer incidence in women aged 50 and over in the Netherlands, 1989 – 2012. From 1989 to 1996, biennial invitation to mammography of women aged 50-69 was implemented. In 1997 women aged 70-75 started to be invited for screening. Digital mammography replaced film-based mammography after 2006 [Ref – 2017].
Another recent assessment of Digital Breast Tomosynthesis with Hologic 3D Mammography Selenia Dimensions System for Use in Breast Cancer Screening in Norway, The Norwegian Institute of Public Health (NIPH) concluded that ‘There is too little evidence to conclude regarding the effects of the use of Hologic digital breast tomosynthesis in combination with digital mammography or synthesized digital mammography compared to digital mammography alone for the outcomes assessed in our report (recall rates, cancer detection rate, interval cancer rate, false positive and false negative rate, sensitivity, specificity, mortality and quality of life). Preparation of a full health technology assessment should be considered when sufficient evidence is available.’ [Ref]
Q4 Overdiagnosis of breast cancer through screening is high and will lead to lot of unwanted surgeries psychological trauma and lead to economic burden.
Do we have evidence for this? YES.
Q5 if there is evidence against mammography screening why is it been continued?
‘In January 2013, the Swiss Medical Board, an in dependent health technology assessment initiative under the auspices of the Conference of Health Ministers of the Swiss Cantons, the Swiss Medical Association, and the Swiss Academy of Medical Sciences, was mandated to prepare a review of mammography screening. The two of us, a medical ethicist and a clinical epidemiologist, were members of the expert panel that appraised the evidence and its implications. The other members were a clinical pharmacologist, an oncologic surgeon, a nurse scientist, a lawyer, and a health economist. As we embarked on the project, we were aware of the controversies that have surrounded mammography screening for the past 10 to 15 years. When we reviewed the available evidence and contemplated its implications in detail, however, we became increasingly concerned.’ Read the complete article [Ref]
More evidence from recent reviews