Breast Cancer Screening

One million women each year will develop breast cancer worldwide and since 1963 many trials have looked at whether screening will affect the outcome in terms of mortality and morbidity. Several countries have now set up screening programmes to call women for routine screening.

The programme was initiated in 1988 following the Forrest Report,¹ and has 80 units across the UK, each responsible for the screening of approximately 45,000 women.²
The budget for the screening is around £75 million.

The breast cancer screening programme in the UK has been set up to allow for the early detection and treatment of breast cancer in women. The ten-year fatality of screen-detected tumours is 50% lower than that of symptomatic tumours.³

• A Finnish study showed 47% reduction in mortality in the 65-69 year-old cohort.⁴ The overall reduction in mortality for 55-69-year-olds was 37%.
• For women aged 40-49 there is only limited evidence of a reduction in mortality. This may be due to the difficulties in interpreting mammograms in pre-menopausal women, due to glandular breast tissue, and also to the lower incidence of breast cancer in this age group.
• Research has shown that the screening programme in the UK has resulted in the saving of approximately 300 lives per year since it began. When the changes to screening were proposed in 2003, it was estimated that this would rise to 1,250 per year by 2010.⁵ A recent report however has shown that the figure has already risen to 1,400 lives per year.⁶
• Recent studies have also suggested that cancerous tumours detected by routine screening have a better outcome as measured by 10-year survival rate, than those tumours detected by other means.⁷
• A Cochrane review concluded that screening is likely to reduce breast cancer mortality.⁸ Based on all trials, the reduction is 20% but, as the effect is lower in the highest quality trials, a more reasonable estimate is a 15% relative risk reduction. Based on the risk level of women in these trials, the absolute risk reduction was 0.05%.

All women between the ages of 50 and 70 are invited to attend for screening every three years. It is a rolling programme, which means that not all women will be invited when they reach 50 years, but all will be invited before their 53rd birthday.

Women over the target age may request mammography through their GP. The Cancer Reform Strategy, published in December 2007, outlined significant changes to the NHS Breast Screening Programme.⁹ It promised to extend the programme to include nine screening ‘rounds’ inviting women between the ages of 47-73 by 2012, with a guaranteed first screening before the age of 50.

In England (2006-2007) 73.8% of women aged 50-64 accepted an invitation to screening.³ The rate is lower (55%) in London where the population can be hard to reach because of its diversity and transient nature.

• 1.9 million women of all ages were screened within the programme.
• 14,753 cases of cancer were diagnosed in women of all ages screened.
• This is an average detection rate of 6.0 cancers per 1,000 women screened. Highest rate = Wales - 6.7 cancers per 1,000 women screened. Lowest rate = Northern Ireland - 5.4 cancers per 1,000 women screened.

Women who have a family history of breast cancer can access advice about their risks and further screening if required, through their GP.

Otherwise primary care clinicians should be aware of women who may be at higher risk of breast cancer, e.g. not breast-feeding long-term, having no children or few children, having children at late ages (especially over 30), obesity (for post-menopausal women only), diethylstilboestrol exposure in-utero and high consumption of alcohol, and advise them opportunistically of breast awareness.

Screening in the UK is a nationally co-ordinated programme, with national standards monitored through a quality assurance network.

Screening takes place in the form of clinical examination and mammography, or X-ray of the breast, which allows small tumours to be detected before they are palpable. Since 2003, two images of each breast have been taken, craniocaudial, and mediolateral, and this increases the detection rate of even smaller abnormalities by up to 43%.²
Other assessment centres may use ultrasound of the breast.

If further investigation is required, fine-needle aspiration cytology may be carried out. Another common technique used in the clinics is core biopsy, which is always done under local anaesthetic.

Screening also leads to overdiagnosis and overtreatment, with an estimated 30% increase, or an absolute risk increase of 0.5%. The current evidence is showing a minor (1%) increase in incidence,¹⁰ if any at all.¹¹ Further, large scale evidence is required.

The current evidence means that for every 2,000 women invited for screening throughout 10 years, one will have her life prolonged.⁸

Although the benefits of screening may be considerable, it can be a very anxious time for many women. Research suggests, however, that women are able to balance the anxiety against the effectiveness.¹²