More clinical trials are needed into the benefits of complementary therapies for cancer patients, says one expert.
Could complementary medicine help beat cancer?
Professor Leslie Walker said many patients benefit from relaxation therapy and "guided imagery" - or visualising the body beating tumours.
The Cancer Research UK scientist says trials should look at the safety and cost of other complementary therapies.
Current trials include the effects of reflexology and scalp massage on 180 women with early-stage breast cancer.
It follows calls from Prince Charles for more research and more complementary therapies on the NHS for cancer patients.
Professor Walker, director of two oncology centres, has been carrying out trials for 25 years to show how they can improve patients' quality of life.
He is examining the effects of relaxation therapy and guided imagery on bowel cancer patients.
He told the International Union Against Cancer Conference in Dublin: "The idea that guided imagery may have powerful psychological and biological effects goes right back to Aristotle who said: 'The soul never thinks without a picture'."
"Relaxation techniques involve muscular exercises.
"Some patients like to imagine a battle scene between the cancer and the drug treatment.
"Others prefer to imagine a healing process like a white light promoting well-being and a return to health."
Complementary and alternative medicines have proved to be a controversial issue.
Prince Charles was reprimanded for his views by a leading cancer expert who told him: "I have no time at all for 'alternative' therapy that places itself above the laws of evidence."
Professor Robert Souhami, Cancer Research UK's director of policy, said some complementary therapies had been shown to be "of value" in some clinical situations.
But he stressed: "It is essential that all such approaches undergo rigorous assessment in randomised clinical trials."