SHM Converge Scientific Abstract ePoster Gallery-Pembrolizumab-Induced Encephalopathy in Triple Negative Breast Cancer

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This case report describes a rare instance of pembrolizumab-induced encephalopathy in a 56-year-old woman with stage IIB triple-negative breast cancer. She had been treated with lumpectomy followed by neoadjuvant chemoimmunotherapy, achieving near-complete remission, but residual disease led to continued pembrolizumab and capecitabine for three months.<br /><br />She later presented with altered mental status. Extensive evaluation for metabolic, infectious, and structural causes, including brain MRI, was unrevealing. Because of concern for autoimmune encephalitis related to pembrolizumab, the drug was stopped and she was treated with high-dose IV methylprednisolone and IVIG. Her condition did not improve initially, so a five-day course of plasma exchange was added. After this, her mental status gradually recovered, she was extubated, discharged to acute rehabilitation, and ultimately achieved full cognitive and motor recovery while tapering prednisone.<br /><br />The authors note that pembrolizumab is a PD-1 inhibitor used in several cancers, including breast cancer, but neurological immune-related adverse events are rare. Common immune toxicities in breast cancer trials included thyroid dysfunction, pneumonitis, colitis, and skin reactions, with no prior encephalopathy reported in this setting. They state this is the first reported case of pembrolizumab-induced encephalopathy in triple-negative breast cancer.<br /><br />The report emphasizes that neurologic immune-related adverse events typically occur weeks after immunotherapy begins and that management includes stopping the checkpoint inhibitor and giving high-dose corticosteroids. In refractory cases, IVIG, plasma exchange, or other immunosuppressive therapies may be needed.

Asset Subtitle

Sagar Patel

Meta Tag

Author List Eric Chan, Margaret Beliveau, Roudi Bachar, Sagar Patel

Category Clinical Vignettes

Concept Pembrolizumab

Concept PD-1

Concept Pembrolizumab-Induced Encephalopathy

Concept Immune-Related Adverse Event

Concept Triple-Negative Breast Cancer

Distinguished Non-Finalist

Presenter Organization Indiana University Southwest Internal Medicine

Presenting Author Sagar Patel

Track Adult

Keywords

pembrolizumab

encephalopathy

triple-negative breast cancer

immune-related adverse event

PD-1 inhibitor

autoimmune encephalitis

high-dose corticosteroids

intravenous immunoglobulin

plasma exchange

neurologic toxicity

Pembrolizumab

PD-1

Pembrolizumab-Induced Encephalopathy

Immune-Related Adverse Event

Triple-Negative Breast Cancer