Pembrolizumab-Induced Retroperitoneal Fibrosis Detected on 68 Ga-FAPi PET/CT.

Agrawal, Neha; Mahdi, Raza A; Singh, Harmandeep; Mittal, Bhagwant R; Kumar, Rajender; Taneja, Sunil · Clin Nucl Med · 2026

case_report · Level V

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Abstract

Hepatocellular carcinoma is one of the leading causes of cancer-related death worldwide. Immune checkpoint inhibitors (ICI) have improved progression and overall survival in patients progressing on sorafenib therapy. But activation of the immune system can lead to numerous immune-related adverse events. Here we present a case of hepatocellular carcinoma with abdominal pain after initiation of pembrolizumab. 68 Ga-FAPi PET/CT highlighted FAPi avid soft tissue density in the paraaortic and presacral regions with diffusely increased FAPi uptake in the thyroid, suggestive of ICI-induced retroperitoneal fibrosis and thyroiditis.

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