Mixed Neuroendocrine-Non-Neuroendocrine Neoplasms (Minens) Of Gastrointestinal (Gi) Tract: A Single Institution Experience

633 Background: MiNENs are heterogeneous group of rare tumors and represent less than 1% of all GI malignancies. These are pathologically classifiable according to neuroendocrine component into low grade, intermediate grade and high grade MiNENs but and managed based upon non-neuroendocrine component rather than true NENs. They have poor prognosis and less is known about treatment options. Methods: We identified 34 cases of MiNENs from 1/1/2000 to 1/1/2018 from Siteman Cancer Registry Database at Siteman Cancer Center, Washington University, St. Louis. Treatment and follow up information was obtained from medical charts of patients. Results: Of 34 identified cases of MiNENs, our database showed equal distribution of MiNENs in male and female patients (N = 17 each). Site of origin included appendix (N = 14), colon (N = 10), esophageal (N = 2), stomach (N = 3), rectum (N = 3), small intestine (N = 1) and ampulla of Vater (N = 1) locations. Histology was high grade (N = 22), intermediate grade (N = 8), low grade (N = 3) and unknown (1). Twenty nine (85%) underwent surgical resection with curative intent and 13 (40%) patients were disease free at five years of follow up. Disease was localized in 15 patients (44%) and distant metastasis were reported in 13 patients (40%). Ten out of 15 patient with localized disease were disease free with combined modality therapy of surgery and chemotherapy. Most common chemotherapy regimen used in the metastatic setting was FOLFOX (11), 5FU/capecitabine (3), and carboplatin plus etoposide (5). Next generation sequencing analysis was available on limited patients which showed MMR proficient (3), MMR deficiency (1), BRAF V600E mutation (1) and KRAS wild type (1). Conclusions: MiNENs of GI tract are rare and aggressive tumors and represent a distinct entity. Surgical resection whenever possible offers curative option. Our database of GI MiNENs showed efficacy with commonly used GI chemotherapy regimens. Patients with low grade tumor histology had better survival as compared to moderately and poorly differentiated tumors. Genomic testing through NGS would be recommended for personalized treatment decisions given poor prognosis in these patients.