Breast cancer screening

From Ganfyd

Jump to: navigation, search

Breast cancer screening programmes exist in several countries. Campaigns for self-examination became less prescriptive with experience as it appears to have no impact on mortality.[1] In the UK, previous advice on regular breast self-examination has been replaced by exhortations to be "breast aware".

X-ray mammography is the most commonly used technical modality, but thermography and ultrasound have also been examined. MRI may have advantages, including usefulness in younger women, greater acceptability and an absence of radiation known to be harmful, but insufficient MRI capacity is available in most places for this to take over.

Many breast screening programmes were introduced on the weight of evidence produced in the 1980s. Improvements in the treatment and management of breast cancer means that the predicted benefit of many screening programmes has fallen below the original projections. Cynics have suggested that the undoubted improvement in mortality with breast cancer owes less to the introduction of screening mammography than to the contemporaneous effect of tamoxifen, and, even, that the net effect of screening with ionising radiation may be negative.

The maximum effectiveness of screening

Around 90% of breast cancers are detected by the womanNeeds citation, benefits from screening therefore apply only to the remaining 10%, unless considerably more predictive techniques were to become available.

LogoWarningBox4.pngInvolvement in screening programmes, particularly this one in the UK, is distinctly dangerous for the doctors, since there will be interval cancers, and blame for these will be directed at doctors. Unlike the cervical cytology screening programme, this does not detect a pre-cancerous stage, therefore it prevents no cancer. Neither technology nor operators are capable of detecting every cancer.

Contents

Evidence

A 2009 Cochrane meta-analysis found that analysis of 3 adequately randomised trials failed to show benefit, although inclusion of other sub-optimally randomised trials showed a modest 15% reduction in mortality at the expense of over-diagnosis and over-treatment of some cancers.[2] Another 2009 analysis of several national screening programmes 7 years pre- and post-screening suggests that as many as 1 in 3 of screen-detected cancers consitute an overdiagnosis, i.e. undetected, the cancer would not have otherwise progressed or shortened life.[3] In a study in Denmark, a screening programme in one region of the country did not appear to reduce mortality compared to the rest of the country.[4] Since then there has been increasing concern around overdiagnosis and long term effects of mammography. While screening is likely to reduce breast cancer mortality it has been estimated for every 2000 women invited for screening throughout 10 years, one will have her life prolonged and 10 healthy women, who would not have been diagnosed if there had not been screening, will be treated unnecessarily. A further 200 women will experience psychological distress for many months because of false positive findings[5].

Flag of USA.png

American interpretation of the evidence base is essentially pro-mammography[6].

UK NHS Breast Screening Programme

Flag of the United Kingdom.png

Originally established following the Forrest report (1986), the UK breast screening programme calls women between the age of 50 and 70 for mammograms every three years.

The recent information leaflets for the programme have been criticised for not including the latest evidence due to the changing epidemiology and issues around overdiagnosis and long term effects of mammography[7].

MRI

The cost of MRI per examination is, in 2006, around 10 times that of x-ray mammography. The younger the patient or the more dense her breasts, and the higher her risk, the more cost-effective this is. The UK NICE guidance attempts to relate provision to absolute risk levels, although these differ according to category. Presence of specific genes (principally BRCA1/2 germline mutations) associated with breast cancer is one of the major factors offered for decision.

External links

References