Rationale:Colorectal cancer is the most common type of cancer leading to death; approximately 10% to 25% of rectal cancer patients present with synchronous colorectal liver metastases. However, the management of synchronous colorectal liver metastases is difficult, especially for patients unable to tolerate chemotherapy or surgery. To date, the optimum treatment of colorectal liver metastasis patients remains controversial, and the curative effect is unsatisfactory. Therefore, we established a novel therapeutic approach to treat colorectal liver metastases employing radiotherapy plus immunotherapy.Patient concerns:A 56-year-old man presented with mucous bloody defecation occurring >20 times a day and accompanied by fatigue and poor appetite. After 4 months, he was admitted to the hospital due to increased fecal blood volume.Diagnosis:Highly differentiated adenocarcinoma was diagnosed based on rectal biopsy, and abdominal computed tomography (CT) showed multiple metastatic tumors in the liver.Interventions:The patient underwent 1 cycle of chemotherapy, which was terminated owing to severe gastrointestinal reactions. Several days later, he was administered cytokine-induced killer (CIK) cell therapy plus adjuvant radiotherapy.Outcomes:Dynamic changes in the patient's tumor markers returned to normal levels, and abdominal CT and abdominal magnetic resonance imaging (MRI) revealed no metastatic liver tumors.Lessons:Sequent therapy provided a curative effect for liver metastasis in a rectal cancer patient. Radiation may have activated the body to produce distant effects, eliminating the live metastasis. CIK cell-immunotherapy and radiotherapy may have synergistic therapeutic effects and could be combined for successful treatment of liver metastasis from rectal cancer.