Endocrine Abstracts

Background: Chemotherapy regimens in GEP-NEN (including neuroendocrine tumours (GEP-NET) and neuroendocrine carcinoma (GEP-NEC)) are not standardized with uncertain outcomes. The available evidence is from small studies. This study aimed to compare chemotherapy use and overall survival (OS) in patients with GEP-NEN from NCRAS and SEER.

Methods: A total of 15,266 and 48,645 patients with GEP-NEN were extracted from NCRAS and SEER respectively. Kaplan-Meier (KM) plots, Univariable and Multivariable Cox Regression (MCR) models were generated to study the effect of chemotherapy on OS. Machine learning (ML) model was developed to predict the factors associated with receiving chemotherapy in SEER.

Results: In NCRAS, 10%, 4.7% and 35% of GEP-NEN, GEP-NET, and GEP-NEC received chemotherapy. For GEP-NEC who received chemotherapy, median age was 64-years. Most were males (63.1%), white (89.7%), living in urban areas (79.7%), had colorectal-NEC (40.3%) and stage 4 (67.0%). A total of 56 and 44 different chemotherapy regimens were used in NEC and NET respectively. The most common regimen was Cisplatin/Carboplatin/Etoposide (24.5%) and Capecitabine/Temozolomide (1.2%) in NEC and NET respectively. In SEER, 8.9%, 3.6% and 28.5% of GEP-NEN, GEP-NET, and GEP-NEC received chemotherapy. For GEP-NEC who received chemotherapy, median age was 61-years. Most were males (60.0%), white (65.4%), living in metropolitan areas (89.0%), had pancreatic-NEC (40.3%), with median size of 48-mm and distant stage (77.3%). In both cohorts, KM plots showed worse unadjusted OS with chemotherapy in overall, NET, and NEC cohorts. In NCRAS, MCR showed that chemotherapy is associated with worse OS in GEP-NEN and better OS in GEP-NEC. In SEER, MCR showed that chemotherapy is not statistically significant in relation to OS in GEP-NEN. However, it was associated with better OS in GEP-NEC. ML showed the most important factors associated with receiving chemotherapy are advanced grade, advanced stage, larger primary tumour, liver metastasis, NEC morphology and younger age.

Conclusion: Chemotherapy is more frequent in GEP-NEC than GEP-NET but overall, surprisingly few GEP-NEC received this treatment. Adjusted analyses may suggest chemotherapy offers some benefit in GEP-NEC only. A variety of chemotherapy regimens were used. This variability highlights the need for improved standardization to enhance outcomes.