Hypnotherapy and cancer pain
A report from the American National Institute for Health in 1996 stated that hypnosis can help to reduce some kinds of cancer pain. A large review in 2006 looked at using hypnotherapy to control distress and pain from medical procedures in children with cancer. The review found that hypnotherapy did seem to help to reduce the children's pain and distress, but it recommended more research.
You can look at this cancer pain review on the Research Council for Complementary medicine website.
In 2012, researchers in Spain again reviewed studies of children with cancer and found that hypnosis appeared to help reduce pain and distress from cancer or from medical procedures.