Rectal cancer in a 90-year-old man needs to choose the best treatment according to the scope of invasion of rectal cancer, which mainly includes surgical treatment, radiotherapy, chemotherapy, targeted therapy, immunotherapy and so on. If currently belongs to the early stage of rectal cancer, the cancer cells have not metastasized and spread, and have not caused pressure on the surrounding tissues and organs, surgery is usually recommended as soon as possible, such as laparoscopic surgery and open surgery. The survival rate of most patients can reach about 60%~70% within 5 years after surgical treatment. If the cancer cells have metastasized and spread after the 90-year-old man got rectal cancer, and the condition has developed to the middle or advanced stage, he can consider total rectal mesentery resection if he can have surgery; if the time for surgical treatment has been missed at present, he can choose radiotherapy, chemotherapy, targeted therapy, immunotherapy and other ways to inhibit the cancer cells.