Rare case of chemotherapy-refractory metastatic vaginal squamous cell carcinoma with complete response to concurrent pembrolizumab and radiotherapy- case report and literature review.

Primary vaginal cancer is a rare malignancy with a lack of international guidelines and supporting clinical trial evidence to guide decision making. Historical results have shown poor outcomes with chemotherapy for stage IVB vaginal squamous cell carcinoma (SCC). The evolving role of checkpoint inhibitors in rare gynaecological cancers prompted us to investigate the role of pembrolizumab in this setting. The efficacy of pembrolizumab in vaginal SCC has never been investigated in any clinical trial. There is established data to support the use of concurrent chemoradiotherapy in gynaecological cancers, however, the data for concurrent use of immunotherapy and radiotherapy is still lacking but is the subject of several clinical trials. We herein present the first reported case of chemotherapy refractory vaginal SCC with complete response to pembrolizumab and concurrent pelvic radiotherapy. We also present wall-eyed bilateral internuclear ophthalmoplegia (WEBINO) as a rare but new immune related adverse event.