Breast screening means thousands get unnecessary and invasive treatment

Mar 5 2006

A team of researchers from Malmo University Hospital in Sweden say the information sent to women about breast screening needs to be more balanced to ensure women are adequately informed about the benefits and harm.

The researchers acknowledge that it is widely agreed that breast screening can reduce deaths but say more discussion is needed on the negative side-effects of over-diagnosis.

They suggest that thousands of women could be getting complex and invasive treatment for breast cancer which they do not need because of "over-diagnosis" during screening.

The scientists believe as many at 10 per cent of positive breast cancer screening results could be cases where the cancer would never have come to the attention of doctors during a woman's lifetime if it were not for screening.

This they say can result in invasive treatment such as surgery and radiotherapy which may never have been necessary if the woman had not attended breast screening.

The research team used data from a breast cancer screening trial in Sweden between 1976 and 1986.

The women who took part in the trial were followed until December 2001, to track survival and detection of breast cancer.

The researchers also examined mammography invitations from English speaking and Scandinavian countries with publicly funded screening to assess whether they provide sufficient information to enable women to make an informed decision.

Thirty invitations (97%) mentioned the main benefit of screening, a reduction in breast cancer mortality, but only seven gave the size of the benefit and none of them in a helpful way.

In contrast, no invitation mentioned the major harm of screening, over-diagnosis and subsequent over-treatment.

Six invitations argued that screening leads to less invasive surgery and another four stated that it leads to simpler treatment.

None of the invitations noted that research has shown that screening leads to increased use of surgery and radiotherapy arising from over-diagnosis.

Fifteen invitations (48%) recommended regular breast self examinations, despite doubts over their benefit and documented harms.

According to the authors although it is good news that the invitations often included an information pamphlet, the focus on the benefits of screening is problematic, as the most important harms, over-diagnosis and over-treatment, were not mentioned and other important harms were often either omitted or downplayed.

Two-thirds (68%) of invitations gave an appointment date, but they warn that this gives the impression that participation is a public duty.

They believe that information material should convey the message that a decision not to attend is not irresponsible.

The researchers say the information included with invitations should be more balanced, using absolute numbers to describe the likelihood of benefits and harms, and applying to the same time span if possible.

They suggest that the responsibility for the programmes should be separated from the responsibility for the information material and that consumer groups be involved in the process of developing balanced information material.

The researchers estimated that the rate of over-diagnosis of breast cancer was 10 per cent in women aged 55 to 69 who took part in the screening trial when comparing the incidence of cancer with a control group of women who were not screened.

Researchers, from the Nordic Cochrane Centre in Copenhagen, say the organisers of publicly funded screening programmes faced a conflict of interest because they want uptake to be as high as possible.

They say the information women are sent about breast screening needs to be more balanced so they know about the benefits and harms.

They also said research suggested women generally exaggerated screening's benefits, but were unaware of the harms.

Cancer experts however are warning that women should not be put off getting tested.

The research is published in the British Medical Journal.