Introduction
Breast cancer has caused mortality for a significant group age of women more than 50 years, and has been a cause of concern among several countries for a long period now. This paper shall try to find out significant methods and case study in breast screening unit.
Discussion
Nystrom et al (2002) found that mammography for women age 50 years in randomised controlled trials reduce mortality from breast cancer by about 25%. The efficacy of mammography in women less than 50 years is uncertain but long-term follow-up of some randomised controlled trials showed benefit of screening in this age-group. The Malmo Mammographic Screening Trial showed a 36% reduction in breast-cancer mortality in the two cohorts of women aged 45–49 years and 43–49 years at entry. They have undergone screening by mammography at 18–24 month intervals at an average follow-up of 15.5 years and 10 years for the two cohorts in this age-group (Andersson et al, 1997).
It has also been noted that many countries already adopted population-based screening that include women from age 50 years and some include younger women too.
Patients and Procedures
In one trial undertaken in 23 NHS breast-screening units in England, Wales, and Scotland, women were identified from lists of patients of general family practitioners or GPs. Individual randomisation was carried out by GPs with prior notification list prepared by the Health Authority for each GP. The GPs identified women for whom to invite for screening, such as those under care for breast cancer.
The whole sample population was followed up through flagging at the NHS central register (NHSCR) to determine breast-cancer incidence and mortality, mortality from all causes, and emigration. The trial specifically looks at the effect on breast-cancer mortality of inviting women to screening from age 40 years compared with invitation from age 50 years as in the current NHS breast-screening programme.
A review of case notes is undertaken to ascertainment cause of death in a number of cancer screening trials. Olsen in 2001 suggested that treatment of early cancers by lumpectomy and radiotherapy might increase the likelihood that deaths among screen-detected breast cancers will be misclassified as death from other causes. This caused bias in the results in favour of screening. Since breast cancer is more likely to be diagnosed in the intervention group of a screening trial, deaths in this group are more likely to be attributed to breast cancer, a bias against screening (Black WC, 2002).
The trial showed an almost equal number of errors in either direction when verified cause of death was compared with that from the death certificate, with an overall bias of less than 1%. This was also seen in reports from Sweden (Nystrom L et al, 1995).
A number of possible harmful effects of screening need to be weighed against any beneficial effects. A potential disadvantage of mammographic screening is the risk of radiation induced breast cancer (Law and Faulkner, 2001). The study calculated the ratio of detected cancers to those induced, assuming annual two-view mammography before age 50 years. If the true benefit-to-risk ratio is lower than the ratio of detected to induced cancers and for some uncertainty in the cancer induction risk factors, Law and Faulkner (2001) estimated that this ratio would exceed 1. This concludes that the advantage of screening would outweigh the risk for women down to age 40 years for all but 2% of women receiving the higher dose.
Another disadvantage includes false positive results. Recall rates for assessment varied from 5% at prevalent screen to 3% at later screens. These figures are lower than those in women aged 50 years and older and to those at subsequent screens would be reduced if two views had been used, but lower cancer detection rate means that the positive predictive value will be reduced.
It was assumed in the case study that once all women in both groups have been invited for their first screen as part of the national programme, any over diagnosis due to screening in the trial should be apparent. The NHS breast-screening programme routinely uses two-view mammography at all screens resulting in improved detection rates and reduced recall rates (Blanks, 2005). The use of two-view mammography in younger women might result in similar benefit but it would also increase radiation dose. Use of double reading in women with dense breasts or in younger women in whom dense breasts are more common was suggested to be of value (Cornford, 2005).
Conclusion
There is certainly need for a safer detection process for breast cancer amongst women at varied age stages. More research that includes ways other than mammography should be explored. In addition, it is important that women are provided with full information about both the possible harms and costs of screening, but more important is for them to be aware of the causes of breast cancer. Prevention is still best.
Reference
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