Gastroenteropancreatic Neuroendocrine Carcinoma (GEP-NEC): An Aggressive Disease Course and Limitations for Personalized Oncology.

Neuroendocrine carcinoma (NEC) is a rare, aggressive malignancy with limited treatment options and poor prognosis. We report a male patient diagnosed with a gastroenteropancreatic (GEP)-NEC with synchronous liver metastasis at the time of surgery who underwent a radical resection attempt. Despite radical-intent surgery followed by adjuvant carboplatin/etoposide, early recurrence developed with progression through multiple subsequent chemotherapy lines. During the treatment process, genetic profiling was performed twice to identify actionable genomic targets, with inclusion in the national IMPRESS study as a last resort. Comprehensive genomic profiling revealed TP53 mutation and RB1 loss but no actionable alterations. A patient-derived organoid (PDO) was successfully established from resected tumor tissue and retained key neuroendocrine and proliferative features, with partial genomic concordance to the primary tumor. Differences between the primary and subsequent PDO in variant allele frequencies suggest clonal selection during culture. Exploratory metabolomic profiling of tryptophan pathway metabolites in patient serum and PDO-culture media indicated tumor-associated metabolic alterations. We present clinical and translational efforts in difficult-to-treat NEC, illustrating both the translational challenges and the potential role of PDOs in advancing personalized treatment strategies for a cancer with very limited treatment options.