LAUSR

Background: Duodenal neuroendocrine tumors (NET) are rare, and few reports have demonstrated the effectiveness of chemotherapy for duodenal NET, with not many other treatment options available. Here, we present a case of unresectable duodenal NET G2 that was effectively treated with streptozocin (STZ) monotherapy. We also perform a literature review. Case Summary: A 57-year-old man presented with multiple lymph node metastasis, liver metastasis, and bone metastasis that occurred after the primary resection of the duodenal NET G2. His long-term survival was obtained; the duration of stable disease exceeded 1 year and 6 months following STZ monotherapy. In addition, his CA 19–9 levels, which previously were increasing, normalized following treatment. Conclusion: To our knowledge, no study has reported the effectiveness of STZ monotherapy for duodenal NET. Our findings demonstrate that for unresectable duodenal NETs, STZ should be first administered as a high volume/single dose to stabilize the disease. However, if the disease progresses, a combination therapy may be effective in obtaining a long-term prognosis of the patient. Furthermore, CA19–9 levels may be an effective factor for determining the therapeutic effect of STZ in NET with other metastases.