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This is a case of a young woman who developed neurological and psychiatric symptoms 3 days after resection of an immature teratoma. She was diagnosed with anti-NMDA receptor encephalitis via positive serum antibody titres, which was later confirmed with cerebrospinal fluid antibody titres. Given her cancer diagnosis, she underwent treatment with bleomycin, etoposide and cisplatin chemotherapy in addition to 5 days of high-dose steroids (1 g of intravenous methylprednisolone) for the encephalitis. This treatment regimen led to significant clinical improvement 3 weeks after completion of one cycle of chemotherapy.

Abdominal pain can arise from numerous sources, including those extra‐abdominal. It is important to obtain additional imaging in the setting of clinical suspicion for malignancy.

Background Cluster of differentiation 26/dipeptidyl peptidase-4 (DPP4) is a cell surface glycoprotein with multifaceted roles, including immune regulation, glucose metabolism, and tumorigenesis. Recent literature has identified DPP4 inhibitors to improve survival in diabetic patients with prostate cancer. DPP4 inhibitors have been proposed to play a role in prostate cancer, as DPP4 is found at higher levels in malignant prostate tissue compared to benign and correlates with PSA levels and cancer stage. In this multi-center retrospective study, we aim to define the effects of DPP4 inhibitors on progression-free survival (PFS) in diabetic patients with advanced-stage prostate cancer. Methodology We performed a retrospective analysis of 161 patients with diabetes and advanced-stage (III or IV) prostate cancer at the University of Florida Health Cancer Center and Moffitt Cancer Center. Our cohort included 120 patients on metformin (control group) and 41 on a DPP4 inhibitor (study group). Results No significant difference in progression of prostate cancer was identified between those on DPP4 inhibitors versus metformin (hazard ratio [HR]: 1.01; 95% confidence interval [CI]: 0.64-1.61; p = 0.955). Median time to progression was 3.5 years (range: 2.4-4.6 years). Conclusions Despite prior literature indicating survival benefit of DPP4 inhibitors in prostate cancer, our study did not identify a statistically significant improvement of PFS in diabetic patients with advanced prostate cancer. Additional analysis with larger sample sizes and prospective investigation with study of tumor microenvironment are needed to evaluate clinical impact and potential survival benefit of DPP4 inhibitors in prostate cancer.

CD26/Dipeptidyl peptidase IV (DPPIV) is a cell surface glycoprotein with numerous roles including glucose metabolism, immunomodulation, and tumorigenesis. CD26/DPPIV is well recognized in diabetes, with DPPIV inhibitors being a class of oral hypoglycemic drugs called gliptins that are commonly used to treat type two diabetes mellitus. Recent work also indicated a potential role for CD26 in infectious diseases, including COVID-19, and immune-mediated disorders such as rheumatoid arthritis, inflammatory bowel disease, and graft-versus-host disease. In cancer, CD26/DPPIV expression has been characterized in numerous tumors such as hematologic malignancies, malignant pleural mesothelioma (MPM), renal cell carcinoma (RCC), hepatocellular carcinoma (HCC), gastrointestinal stromal tumor (GIST), and prostate, lung, colorectal, and ovarian (PLCO) cancer. Hence, CD26 has been frequently studied as a tumor biomarker and therapeutic target. CD26/DPPIV-targeted therapies have been evaluated in various cancers, including the use of anti-CD26 monoclonal antibodies as anticancer treatment in selected neoplasms. This review highlights our current understanding of the role of CD26 in cancer, diabetes, immune-mediated diseases, and infectious diseases. Enhanced understanding of CD26 biology and function may lead to novel therapeutic approaches in multiple human diseases.

OBJECTIVES Primary pancreatic signet ring cell carcinoma (SRCC) is a rare histologic variant of pancreatic carcinoma. A population-based analysis of pancreatic SRCC was performed to determine the predictive effects of epidemiological factors and treatment interventions on overall survival (OS) and disease-specific survival (DSS). MATERIALS AND METHODS The Surveillance, Epidemiology, and End Results registry was searched for pancreatic SRCC cases diagnosed between January 1, 1973 and December 31, 2013. Statistical analysis was performed using the Fisher exact test, χ(2) analysis, Kaplan-Meier method, log-rank test, and Cox proportional hazards regression. RESULTS The mean age among 497 patients was 66.6 years (SD, 11.9). Most patients were white (82.7%) and male (54.5%). The 1-, 2-, and 5-year OS rates were 17%, 9%, and 4%, respectively, while the corresponding 1-, 2-, and 5-year rates for DSS were 18%, 10%, and 5%, respectively. On univariable analysis; age, site, grade, stage, and treatment were predictive of OS and DSS (P

e16546 Background: Radium-223 (Xofigo) has been shown to increase overall survival (OS) in patients with metastatic castration-resistant prostate cancer (mCRPC) via the phase 3 ALSYMPCA study. The side effect of persistent pancytopenia was noted in 2% of the patients, however, the incidence seen in our institutional clinical practice is higher than reported in the literature. This analysis serves to identify predictive factors and thereby help impact future therapy directions in this patient population. Methods: A retrospective analysis was performed analyzing patients with mCRPC who received xofigo at UFHealth in a 3 year span (from January 2014 to January 2017). Data collected included CBC, ECOG functional status, kidney and liver function, evidence of bony disease on imaging, prior chemotherapy regimens, total radiation dose, and PSA. This study was IRB approved. Results: 52 patients with mCRPC were identified, 27 of which received xofigo. 23 patients received treatment at UF, and one was lost to follow-up. 16 patients (73%) completed the full course (6 doses) of xofigo, while 6 did not. 10 patients (45%) developed pancytopenia, with 2 recovering counts within eight months while the other 8 had persistent cytopenias (6 of which were transfusion-dependent). Older age (74.0 ± 8.8 vs 68.7 ± 10.2) and higher ECOG score (1.6 ± 0.7 vs 1.2 ± 0.6) correlated with increased risk of pancytopenia. In addition, a higher percentage of patients who received prior radiation therapy were more likely to develop pancytopenia (90% vs 75%). All patients studied had bony disease and received prior chemotherapy. Conclusions: Albeit with a limited sample size, we found a higher rate of xofigo-induced pancytopenia in our patient population than the 2% reported in the literature. This may influence clinical decision making in the treatment of mCRPC, as pancytopenia may preclude patients from other survival-prolonging therapies. Factors such as age, functional status, and prior radiation therapy are important to keep under consideration prior to xofigo treatment. Additional larger studies are necessary to further quantify this effect.

109 Background: Dipeptidyl peptidase IV (DPP4), also known as Cluster of differentiation 26 (CD26) is a commonly expressed cell surface protein found in many cell types that can function as a tumor suppressor or activator, depending on the cancer type its interactions with the tumor microenvironment. DPP4 has been studied as a tumor biomarker due to its expression in various primary tumors and metastases. Recent literature established benefits of DPP4 inhibitors on progression free survival (PFS) of diabetic patients with advanced colorectal and airway cancers. In this study, we examine the effect of DPP4 inhibitors on PFS in diabetic patients (pts) with advanced-stage prostate cancer. Methods: We performed a multi-center retrospective analysis at Moffitt Cancer Center and the University of Florida of diabetic pts with advanced stage (III or IV) prostate cancer. All pts were on anti-hyperglycemic therapy and received either surgery, radiation therapy, or both for their prostate cancer. The control group included pts on metformin and a sulfonylurea, and the study group included pts on a DPP4 inhibitor and metformin. PFS was calculated for both groups, and Cox proportional hazards regression was used to determine statistical significance. Kaplan-Meier survival analysis was done to predict the effect of DPP4 inhibition and radiation therapy on PFS. Results: Our study population consisted of 161 pts, with 120 pts in the control group and 41 in the study group. No significant difference in progression of prostate cancer was found between those on DPP4 inhibitor vs. Metformin. Specifically, 24 of 41 (59%) of patients on DPP4 inhibitors progressed, while 73 of 120 (61%) of patients on Metformin had progression of prostate cancer (HR 1.01, 95% CI 0.64 to 1.61, p= 0.955). Median time to progression was 3.3 years in the DPP4 group versus 3.5 years in the Metformin group. However, radiation therapy was associated with improved PFS (HR 0.56, 95% CI 0.37 to 0.84, p= 0.0006). Conclusions: Contrary to what has been shown in pts with diabetes and advanced colorectal or airway cancers, exposure to DPP4 inhibitors did not lead to statistically significant improvement in PFS in pts with advanced stage prostate cancer. Recent data suggests that DPP4 may act as a tumor suppressor gene to the androgen receptor (AR) pathway, and that DPP4 inhibition can result in emergence of resistance to androgen deprivation therapy (ADT). Further analysis with larger sample sizes is necessary to elucidate if this is applicable to prostate cancer as a whole, or if this effect is specific to castrate-sensitive prostate cancer (CSPC) vs. castrate-resistant prostate cancer (CRPC).