1499-P: Possible Association of GAD65 Antibody with Pancreatic Adenocarcinoma

Objective: To demonstrate a role of serum anti-glutamic acid decarboxylase 65 antibodies titer (GAD65) as a possible paraneoplastic marker of pancreatic adenocarcinoma.

Case Presentation: A 29-year-old male with polysubstance abuse presented to the emergency room with polyuria, polydipsia, and polyphagia. Laboratory findings were consistent with DKA.

GAD65 antibody was elevated to over 25,000U/mL (0-5- U/mL) leading to a diagnosis of Type 1 Diabetes. The titer was confirmed on dilution and remained unchanged 3 months later Insulin regimen was initiated. Glycemic control was challenging.

Eight months later he presented with epigastric pain, dark urine, and jaundice. An endoscopic ultrasound demonstrated a 7 cm pancreatic head mass with venous abutment. Biopsy revealed a primary adenocarcinoma. Genomic microsatellite testing did not reveal actionable mutations.He underwent 7 cycles of neoadjuvant chemotherapy with Folfirnox; and second-line therapy with radiation and Gemcitabine, Abraxane. Upon completion of these therapies his GAD 65 antibody had decreased to 9,686.3U/mL(0-5 U/mL), his CA 19-9 tumor also decreased to 43.22 U/mL from 47.5 U/mL at diagnosis (0-35 U/mL); while his CEA increased to 4.09 ng/mL from 3.5 ng/mL at diagnosis (0-2.5 ng/mL). His disease is maintained with palliative Folfiri. Glycemic control remains suboptimal.

Conclusion: The degree of GAD65 antibody elevation via enzyme-linked immunosorbent assay could have a role in detecting pancreatic adenocarcinoma. There is no current literature placing the association between GAD65 and pancreatic adenocarcinoma, making this a novel case.