Herbal medicines were by far the most commonly used CAM therapy, the first choice in nine out of 14 countries surveyed by an international research team.
Vitamins and minerals were also among the five most frequently used therapies, according to the responses from nearly 1,000 patients.
The survey is important as it is one of the first attempts to examine use of CAM therapies across Europe. The bulk of the literature on CAM use by cancer patients comes from the US.
Writing in today's issue of the Annals of Oncology (doi:10.1093/annonc/mdi110), the authors said CAM use was found to be considerably lower than surveys reporting results from US samples, where it is often well above 40 per cent.
But their results show that it is used to a sufficient extent - nearly three quarters of cancer patients in Italy use some form of CAM - to warrant an increase in funding for research and better integration into mainstream healthcare services.
"Irrespective of what health professionals believe about CAM and how dismissive they might be, our findings show that patients are using, and will continue to use CAM," write lead author Dr Alex Molassiotis and colleagues.
"So, this will probably necessitate rethinking the provision of medical and healthcare education, broadening our understanding of the concept of medicine and working towards integrating into mainstream healthcare services those CAM therapies for which there is evidence of effectiveness," they claim.
The survey was based on patient questionnaires issued by members of the European Oncology Nursing Society in clinics in 14 countries. It uses the US National Center for Complementary and Alternative Medicine definition of CAM, which includes Chinese and Ayurvedic medicine, spiritual interventions like meditation and prayer, biological therapies like supplements, body-based methods such as massage and energy therapies like Reiki.
The results show that CAM users tend to be female (more than 60 per cent), younger and more highly educated and that pancreatic, liver, bone and brain cancer patients (ie patients with poor prognosis) use CAM significantly more often than other patients.
In most countries around a third used CAM, with only Italy, the Czech Republic and Switzerland showing high levels of use and Greece showing very low levels (under 15 per cent).
Herbal medicines, by far the most commonly used therapy, escalated in use from 5.3 per cent before cancer diagnosis to more than tripling after diagnosis.
Most of the herbs used were specific to each country. For example Turkish patients were most likely to use nettle leaves or tea, while Scots most often reported the use of green tea. In Switzerland patients opted for mistletoe while Serbians and Spanish reported use of aloe vera. Israeli and English patients selected multivitamins.
Homeopathy was also a popular choice across the region - the most commonly used therapy in Belgium - as well as medicinal teas.
Most patients said they used CAM because they wanted to increase their body's ability to fight the disease (50 per cent), improve physical well-being (40 per cent), or emotional well-being (35 per cent).
However, there were some differences in the reasons for using CAM and the actual benefits experienced. For example, although the primary reason for choosing CAM was to boost the ability to fight cancer only 22 per cent found it of benefit.
But overall, patients tended to be satisfied - the mean satisfaction rating was 5.27 on a scale of 0-7, and the mean perceived effectiveness rating was 5.04.
Dr Molassiotis, a reader in cancer and supportive care at the University of Manchester School of Nursing, Midwifery and Social Work, said the study had limitations arising from a variety of difficulties in conducting Europe-wide research.
"Nevertheless, although CAM use in Europe is lower than in the US, our study indicates that the average mean use in Europe has increased since a review of 29 studies was published in 1998," he said.
He added that research funding for CAM has increased but is still very low - only around 0.31 per cent of all medical research funding in the UK - and needs to be significantly increased.
"We cannot overemphasise the need to increase the evidence base of CAM therapies using methodologies that are appropriate and sensitive."
"It's also important from an economic point of view as CAM is a multibillion Euro business - in fact the second biggest growth industry - and some patients pay large sums out of their own pockets to access it."
He concluded that the EU needs to consider broader policies, common laws and rationalisation of available legislation on CAM.