Ganglion Impar Neurolysis for the Improvement of Radiation-Induced Pain During Localized Anal or Perianal Skin Cancer Treatment

This clinical trial studies how well ganglion impar neurolysis works to improve radiation-induced pain during the treatment of anal or perianal skin cancer that has not spread to other parts of the body (localized). Treatment for anal or perianal skin cancer includes giving chemotherapy and radiation therapy (CRT) at the same time. CRT is frequently associated with several side effects, including radiation-induced pain. Despite advances in radiation therapy delivery, patients may still experience side effects which can lead to treatment breaks or treatment discontinuation. Ganglion impar neurolysis is a type of nerve block procedure in which medicine is injected directly into or around a nerve to block pain. The location of the procedure is near the tail bone and the medicine numbs the nerves that are in charge of sensation in the skin by the buttocks and genitalia. This may improve radiation-induced pain in patients receiving CRT for localized anal or perianal skin cancer.