Stage I duodenal adenocarcinoma cured by a short treatment cycle of pembrolizumab: a case report.

The use of Immune checkpoint inhibitor (ICI) therapy (pembrolizumab) in duodenal cancer is rarely reported, and ICI therapy are mostly used in advanced-stage cancer according to its current indication. The case report aimed to demonstrate the special role of ICI therapy in early-stage duodenal cancer and discuss the possibility of modifying and broadening the indication of ICI therapy. A female in her 70s were diagnosed early-stage tubular adenocarcinoma with immunohistochemistry showing deficiency in DNA mismatch repair (dMMR)/high microsatellite instability (MSI-H). Pembrolizumab was selected and the patient was treated regularly for 2 standard cycles. 5 months after the second cycle, the lesion showed no significant change, while 31 months after, the original lesion achieved almost complete remission. ICI therapy may have unexpected effect on early-stage duodenal cancer and more specific indication of ICI treatment may be established. [ABSTRACT FROM AUTHOR]