A case of severe encephalitis while on PD-1 immunotherapy for recurrent clear cell ovarian cancer

Recurrent clear cell ovarian carcinoma is a difficult to treat condition and early trial data has suggested a possible role for immune checkpoint inhibitors. Nivolumab is an anti-PD-1 immunotherapy that has been used in this setting. While immune related toxicity of these agents has been well described, the occurrence of immune specific neurotoxicity is thought to be rare. We present a case of severe encephalitis while on PD-1 immunotherapy for a recurrent ovarian clear cell cancer and we believe this to be the first such reported case associated with the use of PD-1 inhibitor monotherapy. In this case, a 64-year-old woman with persistent clear cell ovarian cancer on Nivolumab presented with a severe fever of unknown origin and delirium; initial imaging and diagnostic work-up suggested a neurological etiology, but with no clear source. We concluded that this was a severe case of immune related encephalitis, thought to be brought about by the anti-PD-1 immunotherapy which responded well to systemic corticosteroids and plasmapheresis and the patient able to make a full recovery. We present a summary of the case and its management as well as a review of the literature on the previously reported neurotoxicity's of PD-1 inhibitors.