Sigmoid ulcerative mass

A 57-year-old woman presented with infra umbilical colicky abdominal pain. The patient has a history of anemia and a blood transfusion a few months ago. The patient underwent a colonoscopy. The scope revealed an inflammatory mass 28 cm from the anal verge, extending up to 10cm towards the cecal side. The lesion showed extensive inflammation, ischemia, ulceration, and necrosis. Biopsies were taken from the anal and cecal edges of the lesion. Histopathology revealed adenocarcinoma grade II. What is your plan of treatment?