To the editor: We hear it often: "Early detection saves lives" - a promise that screening reduces breast cancer deaths.
While this statement is factually true, nevertheless, for every 10 women destined to die of breast cancer without screening, seven or eight of these women will still die even with screening. This is what a breast cancer mortality reduction of 20 to 30 per cent means.
After appraising data accumulated over more than 30 years, the Canadian Task Force calculated that 2,100 women age 40-49 must be screened every two years for 11 years, so that one woman will avoid death from breast cancer. This estimate is consistent with guidelines from the U.S. Preventive Services Task Force in 2009. The miniscule benefit (0.05 per cent) must be balanced against the downside of screening this age group (women aged 40-49). Fully 700 women (of the 2,099 who had no benefit from screening) will have false-positive mammograms, resulting in needless anxiety, unnecessary imaging and painful and intrusive biopsies after which they will be told they don't have breast cancer.
Much worse will be the 10 to 15 women who receive a false diagnosis of breast cancer (over-diagnosis): these women will experience the misery of unnecessary breast cancer therapy: surgery, radiation and chemotherapy, plus the burden of life-long concern about a cancer they never really had.
The good news is that, according to growing evidence, we don't need routine mammography to save even that one life. Numerous studies have shown that, as early as 1985-1990, breast cancer death rates were declining in countries even before they offered screening programs.
Furthermore, breast cancer mortality rates have declined to an equal extent in populations with and without screening programs. In the UK and Europe, where screening is offered only to women 50 and over, mortality rates have declined in women age 40-49 by up to 37 per cent.
Unexpectedly, screening has increased the overall incidence of breast cancer, both invasive and ductal carcinoma in situ. This is largely attributable to over-diagnosis, estimated to be 20 to 50 per cent of all screen-detected breast cancers by researchers outside the imaging industry.
Screening invitations promise that early detection means less radical surgery will occur because the tumours are smaller. Yet a woman's risk of getting a mastectomy (the removal of the whole breast) for a screen-detected cancer increases by up to 20 per cent compared to women in similar populations where screening is not offered.
It is no wonder the public is confused.
The truth of more than four decades worth of research is now very clear: the potential benefit of mammography screening is small and the harms are substantial at all ages, but especially so for women in their 40s.
The bottom line is that mammography screening, implemented to reduce breast cancer deaths due to earlier detection of breast cancer, has been eclipsed by therapy and increased awareness.
Cornelia Baines, Troy Media Corporation.
