Posterior Reversible Encephalopathy Syndrome (PRES) and Drug-Induced Hypersensitivity Syndrome (DIHS) following Immunotherapy and BRAF/MEK Inhibition with Continued Response in Metastatic Melanoma

Background. The role of immunotherapy continues to evolve across both solid and hematologic malignancies. However, while use of immunotherapy has increased via the advent of checkpoint inhibition, chimeric antigen receptors, and vaccines against malignant cells, there remains uncertainty regarding the recognition and management of delayed immune-related reactions and post treatment immune-related sensitivity to subsequent medications, such as BRAF/MEK kinase inhibitors. Furthermore, it is unclear how immunotherapy may alter the adverse effect profile and efficacy of subsequent lines of treatment. Case Presentation. Discussed is a patient with stage IV metastatic melanoma who failed first-line treatment with a combination of nivolumab and ipilimumab. He was then treated with BRAF/MEK kinase inhibition via Encorafenib and Binimetinib. Shortly thereafter, the patient developed posterior reversible encephalopathy syndrome (PRES) and a generalized pruritic rash that was biopsied with consideration toward drug reaction versus drug-induced hypersensitivity syndrome (DIHS), formerly called drug reaction with eosinophilia and systemic symptoms (DRESS). The BRAF/MEK combination was held and steroid taper initiated with continued response even beyond conclusion of the steroid taper. Discussion and Conclusions. This case highlights the diagnostic challenge presented by PRES and DIHS in the setting of immunotherapy and BRAF/MEK kinase inhibition for malignant melanoma. The clinical rationale for reinitiating therapy following severe immune reactions subsequent to immunotherapy in the setting of relapsed/refractory metastatic melanoma is discussed. Additionally, the durable response our patient experienced throughout the drug hold period and steroid taper and its clinical potential etiologies and applications are reviewed. As checkpoint inhibition and tyrosine-kinase inhibitors have become cornerstones of cancer therapy, larger studies and long-term observations are needed to investigate the risks and benefits across different sequences of therapy.