A pathological complete response by chemotherapy with S-1 and oxaliplatin for a locally advanced duodenal adenocarcinoma in Lynch syndrome: a case report

BACKGROUND: Although primary duodenal adenocarcinoma (DA) is a rare malignancy representing ~ 0.5% of all gastrointestinal cancers, the incidence of DA is more frequent in Lynch syndrome. Because of its rarity, treatment strategies or optimal chemotherapeutic regimens have not been clearly defined for advanced DA. CASE PRESENTATION: A 72-year-old woman with Lynch syndrome visited our hospital with a right upper abdominal pain. Computed tomography (CT) showed wall thickness with enhancement in the second portion of the duodenum and adjacent abdominal wall, which suggested direct tumor invasion to the abdominal wall. Upper gastrointestinal endoscopy (UGE) showed a large ulcerative tumor in the second portion of the duodenum, and histological analysis revealed a poorly differentiated adenocarcinoma. A cT4N0M0, cStage IIB (Union for International Control Cancer TNM staging) DA was diagnosed. After three courses of chemotherapy with S-1 and oxaliplatin (SOX), follow-up CT and UGE showed shrinkage of the duodenal tumor. Therefore, the patient underwent pancreaticoduodenectomy with lymph node dissection with curative intent. Histological examination showed a pathological complete response to SOX therapy. The postoperative course was uneventful, and the patient was discharged on postoperative day 29. The patient received no adjuvant chemotherapy, and there has been no evidence of recurrence 6 months after the operation. CONCLUSIONS: SOX therapy provided a remarkable response and can be an optimal chemotherapeutic regimen for advanced DA in Lynch syndrome.