The study is initiated and conducted by the Norwegian Gastro-Intestinal Cancer Group-Colorectal (NGICG-CR). All Norwegian University hospitals and Sørlandet Hospital Kristiansand participate, and all other hospitals that offer diagnosis and treatment of patients with rectal cancer are invited to participate by cooperation with the respective University hospitals.
Among patients treated for locally advanced rectal cancer with neo-adjuvant radio-chemotherapy, about 15% will have complete clinical response in terms of no visible tumor or ulcerations on the site of the primary tumor, or whitening of the rectal wall or telangiectasia. In this Norwegian national multicenter observational study, patients with complete clinical response (cCR) after neo-adjuvant treatment for rectal cancer as defined by national guidelines, will be invited to a Watch&Wait program with a specially designed follow-up in order to see if the tumor has disappeared permanently, or if there is regrowth of the tumor. Primary endpoint is the true regrowth rate in an unselected national cohort of patients.