[A case of residual gastric cancer accompanied by esophageal invasion in which residual lesions were eradicated by half-dose administration of TS-1].

The patient was a 64-year-old male. On November 21, 1991, he underwent gastric resection on the pyloric side for early gastric cancer in the authors' hospital, and did not experience recurrence for many years thereafter. However, endoscopic examination of the upper gastrointestinal tract performed on June 11, 1999 revealed advanced cancer in the posterior wall of the residual stomach which was accompanied by invasion of the esophagus. Thus, the residual stomach was completely removed on July 5, 1999. The histopathological findings were tub1, se, ly3, v2, aw(-), ow(+) and ew(+), and a portion of the esophageal stump and the serosa of the lesser curvature were positive for cancerous tissue. Endoscopic examination was performed one month after the operation, on August 7, 1999. A forceps biopsy taken from an elevated lesion of the esophagus at the posterior wall of the anastomosis revealed adenocarcinoma cells in the lower layer of the squamous epithelium. A residual esophageal lesion was thus diagnosed. Beginning on August 9, 1999, TS-1 was administered in a dosage of 50 mg bid, but it was later learned that the patient had ingested only half of that TS-1 dosage (i.e., 50 mg/day). After completion of one course of this therapy, endoscopy was again performed. It was found that the prominence on the esophageal mucosa at the anastomosis, which had been diagnosed as being cancerous tissue, had shrunk in size, while a forceps biopsy taken from the same site yielded no findings of malignancy. The patient was followed for 18 months thereafter, and endoscopy was performed three times during that interval but continued to yield no evidence of malignancy. As of February 2001, this patient had completed 12 courses of TS-1 at one-half its usual dosage. There have been no findings of recurrence, and the patient's course continues to be good. In summary, this was an interesting case in which residual cancer was detected in the esophageal stump following resection for gastric cancer, and it can be concluded that TS-1 therapy was effective in spite of being incomplete (i.e., half-dose), eradicating the residual cancer tissue.