Breast cancer screening via mammography has long been in the front line of global efforts to reduce death from breast cancer, a disease which killed 2707 Australian women in 2005, second behind lung cancer (2716) as a cause of cancer death.
The core objective in all screening programs is to locate asymptomatic disease, preferably at an early stage, so that it can be treated by surgery, radio or chemotherapy — or often a combination of these. One problem facing all screening exercises is that “indolent” disease can be found which may have not have gone on to become life-threatening. This is a phenomenon well known in the prostate cancer debate, where a large proportion of cancer detected in screening programs is benign (many men live and die with the disease, but not because of it).
The problem is that precision with which benign cancers can be differentiated from aggressive, life threatening cancers can be poor. The result is a lot of intervention, which “wise after the event” can be concluded to have been unnecessary.
Consumers of course have every right to take that gamble when presented with information about the likelihood of a screen detected cancer being dangerous or benign. But many leading cancer epidemiologists are now calling for women to be given more complete information about the probabilities, risks and benefits.
In a multi-signatory letter published today in the UK Times, epidemiologists, breast cancer survivor advocates and other cancer experts from three continents have put it plainly, writing:
…there are harms associated with early detection of breast cancer by screening that are not widely acknowledged. For example, there is evidence to show that up to half of all cancers and their precursor lesions that are found by screening, if left to their own devices, might not do any harm to the woman during her natural lifespan.
Yet, if found at screening, they potentially label the woman as a cancer patient: she may then be subjected to the unnecessary traumas of surgery, radiotherapy and perhaps chemotherapy, as well as suffer the potential for serious social and psychological problems.
The stigma may continue to the next generation as her daughters can face higher health-insurance premiums when their mother’s overdiagnosis is misinterpreted as high risk.
We believe that women should be clearly informed of these harms in order to make their own choice about whether to attend for screening.
Breast cancer screening programs throughout the world jostle with each other to produce the best screening participation rates. Many observers feel that the provision of understandable information about the potentially serious down sides of breast cancer screening would be likely to dissuade some women from participation. So few agencies provide that information, instead providing persuasive rather than balanced information.
Women in Australia wanting to access such information and complete an on-line decision aid to assist their thinking can go here.
Decision aids are also provided for bowel cancer screening, hormone replacement therapy infant vaccination with MMR (measles, mumps, rubella).