A 76-year-old male patient was diagnosed with progressive descending colon cancer. Since the patient had severe respiratoryfunction impairment after right pneumonectomy, the anesthesiologydepartment of our hospital determined that general anesthesia induction was too difficult. He was thus started on capecitabine plus oxaliplatin(XELOX)therapy. Three months after starting this treatment, colonoscopyshowed that the site had become scarred, and tissue examination revealed no indication of malignancy. Accordingly, the patient achieved clinical complete response. The patient had no findings of recurrence 1 year and 11 months after the start of chemotherapy. Chemotherapy for unresectable progressive recurrent colorectal cancer is based on the 5-FU anticancer agent, which exerts its antitumor effect byinhibiting DNA synthesis. The antitumor effect is reportedly high when the expression of thymidylate synthase(TS), a target agent, is low. In this patient, TS expression was low based on tissue examination. TS expression maybe an effective useful predictive factor for the efficacyof chemotherapyadministered to patients with unresectable progressive recurrent colorectal cancer.