Patients with rectal cancer who experience vomiting do not necessarily indicate that their condition has reached an advanced stage; the situation needs to be differentiated and treated accordingly. If nausea and vomiting are due to the gastrointestinal side effects of antitumor treatments such as chemotherapy and radiotherapy, it is unrelated to the severity of rectal cancer. Appropriate antiemetic treatment can provide significant relief. If a rectal cancer patient experiences projectile vomiting due to brain metastases, which lead to an increase in intracranial pressure, it indicates that the disease has progressed to an advanced stage. Some rectal cancer patients may also experience vomiting due to gastrointestinal obstruction caused by the tumor, accompanied by cessation of bowel movements and gas, which are also signs of advanced disease.