It can be very relaxing, but since some Reiki massages don't even touch you, there are limited actual physical benefits, IMO. While tradition massages touch your body and manipulate the muscles, Reiki uses only "healing touch" and sometimes just their hands "manipulating energy"over the body, using 12 to 20 prescribed hand positions, depending on the training tradition. It is considered a type of energy work, and is often used by licensed massage therapists who have taken Reiki training.

In some states, cancer is listed as a contraindication for licensed Massage Therapists, meaning that they are not supposed to treat cancer patients.

My father was a cancer patient who sometimes worked as an inspector for Massage schools and clinics for our state, and his feeling was that if it helps you, and relaxes you, then it is might be of benefit to you. But it is not an actual treatment of any sort.