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Genetic Profiling Of Goblet Cell Carcinoid Of The Appendix Compared To Appendiceal Adenocarcinoma
Trang Nguyen1, *Molly Kledzik2, *Paul Helft1, Eugene Ceppa1, Attila Nakeeb1, C. Max Schmidt1, Nicholas Zyromski1, Michael House1
1Indiana University School of Medicine, Indianapolis, IN;2West Virginia University, Morgantown, WV

OBJECTIVE(S): Goblet cell carcinoid of the appendix (GCC-A) is a rare cancer with a mixed neuroendocrine and epithelial histology. Given the lack of robust clinical data, GCC-A is often treated with the same surgical and systemic therapy guidelines as appendiceal adenocarcinoma. The aim of this study is to compare the genetic profile of GCC-A versus appendiceal adenocarcinoma and mucinous adenocarcinoma using the AACR Project Genomics Evidence Neoplasia Information Exchange (GENIE) Database, one of the largest public cancer genomic data sets.
METHODS: Data from 190 appendiceal adenocarcinoma (A-A) patients, 181 mucinous appendiceal adenocarcinoma (MA-A) patients, and 39 GCC-A patients were analyzed from AACR Genie v 8.1 (released November 2020). Genes mutated in less than two patients were excluded from analysis. Potentially actionable mutations were defined by the OncoKB annotations as having at least investigational evidence of a therapeutic drug.
RESULTS: Appendiceal adenocarcinoma and mucinous appendiceal adenocarcinoma had higher mutation rates compared to GCC-A for KRAS (47.1% A-A, 73.7% MA-A, 2.4% GCC-A), GNAS (17.7% A-A, 46.4% MA-A, 2.4% GCC-A), and TP53 (35.5% A-A, 25.3% MA-A, 7.3% GCC-A). GCC-A tumors had a higher rate of EPHB1 mutations (0.95% A-A, 0.68% MA-A, 12.5% GCC-A) and INHBA mutations (1.0% A-A, 0% MA-A, 9.09% GCC-A). Other commonly mutated genes for all three cancers were SMAD4 (15.6% A-A, 8.4% MA-A, 17.1% GCC-A) and APC (12.3% A-A, 4.2% MA-A, 7.5% GCC-A).
Five patients (12.8%) with GCC-A had potentially actionable mutations or copy number alterations (ERBB2, NRAS, PIK3CA, FGFR1 Amplification), while 31 (16.3%) of A-A patients and 29 (16%) of MA-A patients had potentially actionable mutations or copy number alterations.
CONCLUSIONS: The genetic landscape of goblet cell carcinoid of the appendix is distinct from appendiceal adenocarcinoma and mucinous adenocarcinoma even though traditionally these appendiceal neoplasms have been treated with similar chemotherapy agents. Obtaining molecular profiles of these appendiceal tumors can help identify potentially actionable mutations and personalize treatment options for patients with these rare tumors.


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