But while CAMs may improve the quality of life for cancer patients, there is little evidence that they either prevent or treat breast cancer, Britain's only professor of complementary medicine Edzard Ernst will tell the 4th European Breast Cancer Conference in Hamburg, Germany today.
"If an effective CAM treatment or preventative measure emerged (say, a herbal medicine) it would instantly be taken up by mainstream oncology, as has happened with taxol, which comes from the yew tree. It follows, almost automatically, that all existing CAM 'cancer cures' are bogus," he said.
Yet the use of CAM appears to be increasing across Europe: half of general practices in England now offer patients some access to complementary or alternative medicines, and CAM is well established in Germany, apparently in dialogue with conventional medicine, noted Dr Gillian Bendelow, a reader in medical sociology at the University of Sussex, UK.
This underlines that other motivations, rather than effective treatment, are driving the use of supplements and other remedies by cancer patients, who are following a wider trend among today's consumers.
Problems in categorising CAMs and the lack of research make it difficult to assess their popularity with cancer patients, particularly in Europe, but predicted trends indicate a strong uptake.
"The few studies I have been able to find confirm higher rates of CAM usage among breast cancer patients in Europe: between 50-70 per cent in England and a Swedish study indicating 85 per cent take-up."
She added that a 2003 study in Muenster, Germany, interviewed 203 women with breast cancer who had undergone surgery as first therapy. Of these, 78 per cent used some form of CAM - most common were vitamin preparations at 67 per cent - and 70 per cent used a combination of two or more therapies.
More research is needed to understand how patients and practitioners are making decisions about CAM usage in breast cancer. But some of the main motivations are improving quality of life, giving women more control and greater responsibility for their care, and the need to explore all possibilities.
Studies of cancer patients and the general public show that those who seek CAMs tend to be better educated, of higher socio-economic status, female, and younger than those who do not. Typically, they are more health-conscious and use more mainstream medical services than non-CAM users, said Dr Bendelow.
"They may decide to use CAM without consulting practitioners and it is likely that higher estimates of the numbers of users reflect the growing availability of over-the-counter and internet remedies," she added.
But while many CAMS are promoted for cancer prevention or cure, there is scarce scientific data to support such claims, warned Professor Ernst, from the Peninsula Medical School, UK.
He cited Essiac (a Canadian herbal mixture), Hoxley formula (herbal mixture), mistletoe, laetrile (derived from the seeds of bitter almonds and apricots) and shark cartilage, as typical of these claims, adding that several of these alleged cancer 'cures' are associated with significant risks.
"Examples of risk include the adverse effects of herbal remedies, contamination or adulteration of herbal remedies, their interaction with prescribed drugs, and patients choosing to use an ineffective CAM instead of life-saving conventional treatment," said Ernst.
Growing use of CAM therefore makes it crucial that more, properly conducted studies on the therapies are carried out, added Dr Eric Winer, an associate professor of medicine at Harvard University and director of the Breast Oncology Center at the Dana-Farber Cancer Institute.
"Issues of safety with CAMs are critical. But in many cases, extensive safety evaluation has not been undertaken. Moreover, relatively few CAMs have been tested in conjunction with standard treatments and this is a serious problem."
He adds that it is not necessary that all therapies show a survival benefit. "Survival is important, but treatments that improve quality of life clearly have a place, and not all medical therapy prolongs survival. Having said that, a treatment needs to demonstrate that it can either prolong survival or improve quality of life if it is to be considered for use."
"If any CAM is to be used widely it should be shown to be safe, particularly if it is being used concurrently with another therapy, and that it has some beneficial impact on the patient. Few CAMs have undergone the type of careful scrutiny that I feel is needed," he says.