Manual therapies use things like therapeutic massage to enhance the quality of life, improve coping, and reduce symptoms of cancer patients. They do not directly prevent or treat cancer in any way.
One research article (1) looked at manual therapies (like therapeutic massage). They noted that, while manual therapies can be helpful in reducing symptoms in cancer patients, it is not a good treatment for cancer.
It also noted that more research studies need to be done in order to see if manual therapy can be beneficial on its own to treat cancer patients, or if it helps just because there is a therapeutic relationship between the massage therapist and the cancer patient.
Sources: 1.Sagar SM, et al. Massage therapy for cancer patients: a reciprocal relationship between body and mind. Curr Oncol. 2007 Apr; 14(2): 45–56.