Remarkable response of gastric adenocarcinoma with <i>FGFR2-TRIM44</i> fusion to pemigatinib: a case report

Fibroblast growth factor receptor 2 (FGFR2) gene fusions are detected in 10%-16% of cholangiocarcinomas but are rarely detected in other solid tumours. Herein, we report the case of a 59-year-old woman with stage IVB gastric cancer (UICC 8th edition) characterized by FGFR2-TRIM44 fusion and FGFR2 amplification. Her tumour progressed despite multiple lines of standard chemotherapy. Plasma ctDNA analysis revealed these alterations, and pemigatinib was recommended by an expert panel. Treatment led to a remarkable clinical and radiological response, and she remained on pemigatinib with stable symptoms for 5 months. According to the C-CAT database, FGFR2 amplification was identified in 4.9%, while FGFR2 fusions were identified in only 0.26% of 3116 oesophagogastric adenocarcinomas, with FGFR2-TRIM44 fusions detected in just 0.064%, including our case. Targeted therapies based on genomic information are limited in the treatment of advanced gastric cancer. Thus, this case suggests that pemigatinib may represent a promising targeted therapy option for patients with advanced gastric cancer harbouring FGFR2 alterations.