Breast cancer screening

A group of health professionals has said that women are not being warned of the risks associated with routine breast cancer screening, with many tests ending in unnecessary treatment. Several newspapers have reported on a letter to The Times by Professor Michael Baum from University College London (UCL) and 22 others.

The letter says that women in this country are not given enough information about the potential harms associated with breast cancer screening, and that for every 2,000 women screened, one will benefit (by having her life saved), but 10 will have unnecessary treatment.

However, screening is an emotive and contentious issue and, as the letter acknowledges, there is some debate about these numbers. The Director of the NHS Cancer Screening Programme has said this number is estimated to be nearer four or five lives saved and four or five women that might have been unnecessarily treated.

The NHS Cancer Screening Programme has stated it is committed to giving women informed choice, and full information is available on the website, www.cancerscreening.nhs.uk. The printed literature is under review and the aim is that it will be republished by the end of 2009.

Where did the story come from?

Professor Michael Baum, Emeritus Professor of Surgery at UCL, wrote a letter to The Times criticising the information that is given to women who are invited to attend NHS breast cancer screening. The letter is signed by 22 others representing public health, oncology, GPs, epidemiology and patients. The letter was published in The Times on Thursday February 19.

The letter also mentions an article recently published in the British Medical Journal (BMJ ). This article, ‘Breast screening: the facts—or maybe not’ is an analysis of this issue and was written by Peter Gotzsche and colleagues from the Nordic Cochrane Centre.

What is the NHS Breast Screening Programme?

The NHS Breast Screening Programme was set up in 1988 on the recommendation of an expert committee chaired by Sir Patrick Forrest. The committee considered the evidence supporting and practicality of setting up routine breast cancer screening in the UK. It concluded there was a convincing case for women who did not have symptoms of breast cancer to be screened for the disease.

The Screening Programme invites women age between 50 and 70 to attend a free breast screening examination every three years. It has high coverage: 1.9 million women were screened in the UK in 2007. The 2008 annual report of the Breast Screening Programme says that the programme is estimated to save 1,400 lives every year.

As well as detecting “true” breast cancer, screening also detects women who have ductal carcinoma in situ (DCIS), a breast disease that may not develop into cancer. These are precancerous lesions contained in the milk ducts. Untreated DCIS can develop into invasive disease, but many untreated women never go on to develop invasive breast cancer.

What interpretations do the researchers draw from their analysis?

In their analysis in the BMJ , Peter Gotzsche and colleagues discuss the results of a survey they conducted three years ago. This survey looked at the information given to women invited for mammography breast screening in six countries: Australia, Canada, Denmark, New Zealand, Norway, Sweden and the UK. The survey concluded that there was no mention of the major harms associated with screening (over-diagnosis and subsequent over-treatment) and that some of the information about the benefits of screening was misleading.

In this recent analysis, the authors say that “little has changed” since then, and that although the UK information leaflet has been updated, the content has not changed very much and does not reflect the recommendations they made in their article in 2006. They say they have drafted an alternative evidence-based leaflet to help women decide about whether or not to be screened for breast cancer. They say the alternative leaflet describes the benefits and harms of screening in numbers that can be understood easily. For example, they say the benefits can be described as follows: “If 2000 women are screened regularly for 10 years, one will benefit from the screening, as she will avoid dying from breast cancer”. Harms can be described as: “At the same time, 10 healthy women will, as a consequence, become cancer patients and will be treated unnecessarily. These women will have either a part of their breast or the whole breast removed, and they will often receive radiotherapy and sometimes chemotherapy”.

What does the NHS Knowledge Service make of this study?

Screening is an emotive and contentious issue. Discussions about the balance of benefits and harms, particularly in screening for breast cancer, have been going on for many years.

Many of the harms associated with screening relate to the uncertainty surrounding a diagnosis of DCIS that has been detected by screening. Only half of the women diagnosed with DCIS will go on to develop invasive disease. However, it is not possible to know who will develop it, so all women with screen-detected DCIS are treated in the same way with surgery, radiotherapy or chemotherapy. For women who would never have gone on to develop breast cancer in their lifetime, these are unnecessary treatments and the harms associated with them outweigh the benefits. The letter to The Times says the analysis concludes that for every 2,000 women who are screened for breast cancer over 10 years, one woman’s life will be saved and 10 women will have unnecessary treatment. However, as the letter acknowledges, there is debate about the numbers.

Professor Julietta Patnick, Director of the NHS Cancer Screening Programmes, has said this number is nearer an estimated four or five lives saved and four or five women being unnecessarily treated. So, instead of being a ratio of one life saved to 10 receiving unnecessary treatment, it is much nearer to a one to one ratio.

It is important to point out that the Nordic Cochrane Group who wrote the analysis mentioned in the letter do not refute the effectiveness of breast cancer in reducing mortality. A systematic review of the evidence that the group carried out concluded that “screening likely reduces breast cancer mortality”, about a 15% relative risk reduction. In this particular article, they are highlighting the importance of ensuring that women who are invited to screening are fully informed of both benefits and harms.

The NHS Cancer Screening Programme has stated it is committed to giving women informed choice, and that full information is available on the website, www.
cancerscreening.nhs.uk. The printed literature is under review and the aim is for it to be republished by the end of 2009.