Early breast cancer detection is the aim of screening by mammography.

 

The merits of a screening test are listed inscreening tests. With reference toQ32.8:-

breast cancer is an important health risk (A). There are 24,000 new cases and 15,000 deaths reported annually in theUK .

Breast cancer is the commonest cancer in women in theUK (B). One women in twelve (7.5%) will develop breast cancer at some time in her life.

The majority of breast cancers are found in women over the age of 55 years. We know a lot about the natural history of the disease (C). When the tumour is limited to a duct or measures less than 1 cm, spread to the lymph glands is least likely to have occurred. Screening aims to detect this early stage of disease.

The five year survival for stage 1 breast cancer (less than 2 cm) with appropriate treatment is 84% whereas it falls to 18% for stage 4 disease (D). TheUK screening programme (mammography) costs 37 million per year.

An evaluation in 1986 found that the cost per quality-adjusted life year (a year of good health quality) achieved by screening compared favourably to other approved and established screening programmes (E).

Mammography has high specificity (low false negatives – (F)

and sensitivity (low false positives - G).

In the three years from 1992, 4,729,003 women aged 50-65 were offered mammography – 3,582,332 (75.8%) accepted (H). Breast biopsies were required for 24,651 women (0.69% of those having mammograms. Breast cancer was identified 19,792 (0.55%). Cancer of 1 cm or less was found in 5,785 (0.16%).

It is not known if all invasive breast cancers begin as ductal carinoma in situ lesions (pre-malignant). Not all early abnormalities undergo calcification and mammography, looking for calcification, may not be the most effective way of diagnosing early lesions. A prospective study from Germany has compared mammography with MRI. The MRI proved more effective in diagnosing early lesions.0701

Being screened for breast cancer reduced breast cancer deaths by 48% in a study in East Anglia following the introduction of screening in 1989.2008

It might be assumed that computer assisted detection of abnormality on mammography would enhance interpretation. In practice, the use of computer-aided detection is associated with reduced accuracy of interpretation of screening mammograms. The increased rate of biopsy with the use of computer-aided detection is not clearly associated with improved detection of invasive breast cancer. 0702

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