Diagnosing breast cancer early and efficiently is a critical component of any strategy aimed at decreasing breast cancer mortality in developing countries. In this chapter, I evaluate the evidence behind screening strategies and its controversies. The effect of breast-cancer screening has never been formally evaluated in developing countries, and data from the major screening trials need to be viewed in this context. Screening asymptomatic women by means of breast self-examination, clinical examination or mammography can play a significant role in decreasing breast-cancer mortality in developing countries. Major programmes should not be implemented, however, until adequate diagnostic and therapeutic facilities are in place. The most fundamental interventions in early detection, diagnosis, surgery, radiation therapy, and drug therapy must be integrated, organised and resourced appropriately within existing healthcare structures.
Introduction
Breast cancer is the most common cancer affecting women worldwide. Globally, about 1.3 million new cases are diagnosed annually. The incidence is highest in developed countries, but it is also increasing at alarming rates in middle- and low-income countries, where it is overtaking cervical cancer as the most frequent malignancy diagnosed in women. Mortality from breast cancer has decreased significantly in developed countries over the past few decades as a result of earlier diagnosis and wide availability of multimodality therapy.
Screening for breast cancer has intuitive appeal. Diagnosed at an early stage, the disease has a better prognosis and requires less treatment. Both the individual affected and society as a whole should derive a clear benefit. Many support this, and some of the mammogram screening trials report a 30% reduction in breast-cancer mortality. The evidence derived from these now historical trials, however, has been the subject of great and often acrimonious debate, with some investigators concluding that the claims of benefit of screening are not valid, and that the harms are under-reported and not sufficiently emphasised. Furthermore, breast-cancer screening programmes have not been studied in poorer countries, and it is uncertain how or if data on cost-effectiveness and affordability from developed countries are applicable to women in developing countries.
Definitions and principles of screening
Breast-cancer screening programmes should adhere to accepted parameters ( Table 1 ), such as those published by the UK screening guidelines group.
| The Condition |
| The condition should be an important health problem |
| The epidemiology and natural history of the condition, including development from latent to declared disease, should be adequately understood and there should be a detectable risk factor, disease marker, latent period or early symptomatic stage |
| All the cost-effective primary prevention interventions should have been implemented as far as practicable |
| If the carriers of a mutation are identified as a result of screening the natural history of people with this status should be understood, including the psychological implications |
| The test |
| There should be a simple, safe, precise and validated screening test |
| The distribution of test values in the target population should be known and a suitable cut-off level defined and agreed |
| The test should be acceptable to the population |
| There should be an agreed policy on the further diagnostic investigation of individuals with a positive test result and on the choices available to those individuals |
| If the test is for mutations the criteria used to select the subset of mutations to be covered by screening, if all possible mutations are not being tested, should be clearly set out |
| The treatment |
| There should be an effective treatment or intervention for patients identified through early detection, with evidence of early treatment leading to better outcomes than late treatment |
| There should be agreed evidence based policies covering which individuals should be offered treatment and the appropriate treatment to be offered |
| Clinical management of the condition and patient outcomes should be optimised in all health care providers prior to participation in a screening programme |
| The screening programme |
| There should be evidence from high quality Randomised Controlled Trials that the screening programme is effective in reducing mortality or morbidity |
| Where screening is aimed solely at providing information to allow the person being screened to make an “informed choice” (eg. Down’s syndrome, cystic fibrosis carrier screening), there must be evidence from high quality trials that the test accurately measures risk |
| The information that is provided about the test and its outcome must be of value and readily understood by the individual being screened |
| There should be evidence that the complete screening programme (test, ∗diagnostic procedures, treatment/ intervention) is clinically, socially and ethically acceptable to health professionals and the public |
| The benefit from the screening programme should outweigh the physical and psychological harm (caused by the test, diagnostic procedures and treatment) |
| The opportunity cost of the screening programme (including testing, diagnosis and treatment, administration, training and quality assurance) ) should be economically balanced in relation to expenditure on medical care as a whole (ie. value for money) |
| There should be a plan for managing and monitoring the screening programme and an agreed set of quality assurance standards |
| Adequate staffing and facilities for testing, diagnosis, treatment and programme management should be available prior to the commencement of the screening programme |
| All other options for managing the condition should have been considered (e.g. improving treatment, providing other services), to ensure that no more cost effective intervention could be introduced or current interventions increased within the resources available |
| Evidence-based information, explaining the consequences of testing, investigation and treatment, should be made available to potential participants to assist them in making an informed choice |
| Public pressure for widening the eligibility criteria for reducing the screening interval, and for increasing the sensitivity of the testing process, should be anticipated |
| Decisions about these parameters should be scientifically justifiable to the public |
The World Health Organization defines countries with limited resources as those countries with low- or medium-level resources. Key distinctions between ‘early detection’ and ‘screening’ should be noted. Early detection is the identification of breast cancer at a time in its natural history when it can be treated and potentially cured with the least physical effect. This is typically diagnosed after a woman presents to a healthcare worker with a symptom and requests a medical intervention. By comparison, screening for a disease means using tests on asymptomatic women or populations who are unaware of the conditions and who have not specifically sought medical intervention.
Early detection without screening entails education of the population and healthcare providers to respond to the first signs or symptoms of breast cancer. By teaching women to see providers when they first note changes, and by teaching providers to evaluate changes when they are first noted, cancers potentially can be diagnosed at earlier (although still clinically apparent) stages. Early detection programmes that consist of education require the fewest resources, are an appropriate first step in countries with limited resources, and may have the greatest effect in countries in which women commonly have advanced breast cancer at diagnosis.
Opportunistic screening is when an individual women, who has no symptoms of breast pathology, is referred for screening tests (usually a mammogram) outside of a formal programme. Opportunistic screening may facilitate early diagnosis of non-palpable breast cancers, but only among those individual women who have resources to have these tests and the necessary follow-up diagnostic tests. If the result is abnormal, then the clinician and the patient assume responsibility for further investigation.
Organised or ‘systematic’ screening refers to the establishment of a formal screening programme for a specific population by a facility, institution, regional government or national health care ministry. It is the approach most likely to achieve early detection among a broad segment of the population, but it is also the most resource-intensive screening approach to early detection. It is incumbent on the authorities promoting such programmes to have adequate resources and infrastructure, to have the infrastructure to manage women with abnormal investigation results, and to treat women diagnosed with cancer ; unfortunately this is not the case in most developing countries
Methods of screening
Three methods of screening for breast cancer have been studied and proposed: breast self-examination (BSE), clinical breast examination by a health practitioner (CBE), and mammography. Mammography is the only modality that has been shown to affect breast-cancer mortality.
In BSE, a woman is a formally taught to examine her own breasts. She should inspect the breasts in front of a mirror for dimpling or asymmetry, and then systematically examine each breast by palpation using the contralateral hand, with the ipsilateral arm raised. This is done in both supine and standing or sitting positions. Squeezing the nipple is discouraged. A thorough BSE can take up to 15 min to carry out Participating women are encouraged to do this on a monthly basis. A systematic programme of BSE screening generally includes one or more instruction sessions, either with individual women or groups of women, taught by a trained instructor. Printed educational material and a system to encourage and remind women to practice BSE regularly are used. A formal BSE screening programme is, therefore, a significant undertaking, requiring the use of public-health resources and facilities.
Clinical breast examination by a health practitioner is a standardised clinical interaction whereby a healthcare provider examines a woman’s breasts, chest wall, and axillae. Typically, this begins with an inspection in the upright position for the typical signs of breast cancer, such as dimpling, oedema, erythema, asymmetry, and is followed by a systematic palpation of both breasts and axillae in sitting and supine positions. Clinical breast examination by a health practitioner can be either a screening test or a diagnostic test, depending on the circumstances.
In mammographic screening programmes, women undergo a dual-view mammogram (cranio-caudal and oblique or lateral views) of both breasts. Consensus on the age at which mammographic screening should start and the frequency of mammograms is lacking. Some groups suggest screening should begin at age 40 years, others 50 years, with frequency varying from annual to every two or 3 years. Similarly, consensus is lacking on whether women should have a clinical breast examination at the time of screening or a mammogram alone.
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