Prolonged response to osimertinib in three patients with refractory metastatic pancreatic adenocarcinomas with EGFR exon 19 deletion: a case report and literature review.

Pancreatic cancer is a rising cause of cancer death. Therapeutic options are scarce and of limited efficacy. Up to 26% of patients with metastatic pancreatic cancer could benefit from targeted therapies. We report here for the first time the case of three patients with metastatic pancreatic ductal adenocarcinoma (PDAC) without KRAS alteration for whom an activating mutation in exon 19 of the epidermal growth factor receptor (EGFR) gene was found through mainstreaming NGS. The EGFR variant was confirmed on multiple tumor samples and by circulating tumor DNA (ctDNA) analysis in two patients. The three patients were treated with osimertinib with early molecular, biologic, and morpho-metabolic responses. At the last follow-up, one patient had an ongoing response after 17 months, and disease control had been maintained for 8 and 6 months in the other two. Known resistance mechanisms were observed on ctDNA analysis at progression. These observations demonstrate the benefit of osimertinib for treating EGFR-mutated PDAC and highlight the interest in investigating rare molecular alterations, especially in patients without KRAS alterations.