Screening modalities

Screening modalities

There are three basic potential mass screening tools:

mammography, physical examination by trained staff and breast self-examination (BSE). Mammographyhas been shown to be effective in reducing breast cancer mortality. The Swedish Two County used single mediolateral oblique view Trial mammography alone and achieved a mortality reduction of 32% in women aged 40ñ74. The sensitivity was 91ñ100% for women aged over 50 and 83% for women in the 40ñ49 age group. This maybe due to denser breast tissue in younger women,and sensitivity could possibly be improved by using two-view mammography. The main reason for using a single view in this case was the perceived need in the 1970s to minimise radiation dose.As has already been discussed, with modern mammography techniques this risk is now insignificant.A has study of one- versus two-view mammography shown that by adding a second (craniocaudal)view,the sensitivity of screening during the prevalence round of a population screening programme was increased from 83% to 89% and 14 additional cancers were detected out of a total of 217. The recall rate was also reduced by the addition of a second view, from 8.8% to 6.6%. In conclusion,mammography, particularly with two views, is effective, acceptable and sensitive as a primary screening method.

The effectiveness of clinical examination alone has not been tested, although some trials have used it in conjunction with mammography. In Edinburgh between 1979 and 1981, 45130 women were entered into a randomised controlled trial in which At approximately half were invited to screening.the prevalence round, the study group were offered two-view mammography and clinical examination.Subsequent screens involved clinical examination alone in years 2, 4 and 6, and one-view mammog-raphy plus clinical examination in years 3, 5 and 7.

Although the compliance at the initial screen was poor (61%), and fell at subsequent screens, there did not appear to be any difference in the acceptance of clinical examination and mammography.An analysis has shown the sensitivity of mammography to be 63% and that of clinical examination to The Edinburgh data lack statistical be 40%.power, however, and there is no conclusive evidence to show that clinical examination is effective in reducing mortality. Similar analyses on the HIP data result in sensitivities of 39% and 47% respectively for mammography and clinical examination.

BSE is very difficult to assess, as the only intervention possible is education, and failure to practise seems to be a major disadvantage to the use of BSE as a sole screening method. The sensitivity of BSE is very difficult to measure, but it is assumed that frequent BSE will enable a woman to detect a cancer earlier than less frequent visits for a professional clinical examination. There is some evidence that BSE may lead to a reduction in tumour size at
There is no evidence that BSE diagnosis.contributes to a reduction in mortality, but women should not be discouraged from practising it, as it may contribute to an earlier diagnosis.

Magnetic resonance imaging (MRI) is a relatively new technology that has been shown to have high sensitivity for detecting abnormalities in the 18ñ23 In general, the population at greatest risk breast. Of breast cancer is that of women over the age of 50.In this group, X-ray mammography has been shown to be a relatively cheap, quick and effective modality for breast screening. It is therefore not appropriate to consider MRI as a mass screening tool in the same way. It is more expensive, resources interms of machines and expertise are scarce at present, and scans and their

analyses can be time consuming. However, MRI may have a particular application in screening younger women (aged less than 50) who are at high risk of developing breast cancer. In these
younger, premenopausal women,the breast can be mammographically dense and mammograms are often difficult to interpret.

There is a recognised need to screen women at high familial risk of breast cancer, since the disease may develop at an earlier age than in the general population, but there are concerns
about repeated radiation exposure. With the advent of genetic testing,groups of women at high risk will be identified, for whom X-ray mammography does not provide a satisfactory method of screening for breast cancer.MRI avoids radiation exposure while providing
high sensitivity in detecting breast cancer, even in the mammographically dense breast. Its role in screening is currently under evaluation. Two studies to assess the effectiveness of annual MRI scans compared with annual mammography in the high-genetic-risk group have recently reported from The sensitivity of Canada and the Netherlands.MRI versus mammography in the Canadian and Dutch studies are 79% versus 32%, and 79.5% versus 33.3% respectively. A similar MRC-funded study (MARIBS) was recently published in the UK.

Another group who are considered at high risk of breast cancer are women who have been previously exposed to supradiaphragmatic radiotherapy for MRI is currently Hodgkinís disease at a young age. recommended for breast screening in this group for young women (aged 25ñ29) and those aged 30ñ50 who have dense breasts. No screening is recommended for women aged 25 or under; women aged 30ñ50 with predominantly fatty breasts should have annual two-view mammography; women over the age of 50 will have 3-yearly mammography as normal in the NHSBSP.

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