Immunotherapy for endometrial cancer.

Advanced recurrent endometrial cancer (EC) has a poor prognosis and new treatment options are needed. In 2013, EC was classified by genomic analysis into four groups: the POLE ultra-mutated group, the MSI-high hypermutated group (MSI-H), the copy number low group, and the copy number high group. The prognosis differs based on the classification, which should enable the individualization of treatment. The MSI-H and POLE types can induce PD-L1 expression in cancer cells. Among the gynecological cancers, EC exhibits the highest levels of PD-1 and PD-L1 expression and has the highest proportion of MSI-H. Thus, an immune checkpoint inhibitor (ICI) is expected to be effective. The first ICI to show efficacy in recurrent EC was the anti-PD1 antibody pembrolizumab, which exhibited efficacy in MSI-H EC. The combination of pembrolizumab and the multi-kinase inhibitor lenvatinib significantly prolongs OS/PFS compared with single-agent chemotherapy in previously treated recurrent EC, regardless of MSI status. ICIs are now moving from second-line and beyond to first-line treatment regimens. The efficacy of paclitaxel plus carboplatin (TC) and ICI combinations compared with TC have been demonstrated, including an ongoing Phase III trial comparing chemotherapy with the combination of pembrolizumab and lenvatinib. Although ICIs are becoming the mainstay of EC, they cause systemic inflammatory side effects known as irAEs. The incidence of irAEs is higher for combination therapy with CT or lenvatinib compared with ICI therapy alone. Even though they are rarely fatal, irAEs should be addressed promptly.