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**Abstract:**



AMA Research Challenge 2023

Examining Discrepancies Between Preliminary and Final CT Readings for ED Admits After Hours and its Impact on Surgical Decision-Making: Results of a Pilot Study

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Objective: Gabapentinoids are commonly prescribed to peripheral artery disease (PAD) for pain management. In this study, we investigate the impact of the history of gabapentinoids on postoperative risk of opioid-related disorders in PAD patients undergoing lower extremity bypass (LEB) Operation.

Methods: This is a retrospective propensity-score matched analysis of patients undergoing peripheral arterial bypass in TriNetX, a multicenter population-level database with 213 million patients from 92 health care organizations in the US. Two study groups were constituted based on the pre-surgical history of prescribed gabapentinoids. Group I comprised PAD patients who were using gabapentin or pregabalin prior to LEB. Group II comprised PAD patients who were not using either gabapentin or pregabalin prior to LEB. Patients with history of opioid-related disorders prior to LEB were excluded from the study. The patient population was matched (based on age, gender, and diabetes mellitus) using propensity score matching for balancing the groups and controlling for potential confounders. Primary outcomes were opioid-related disorders and mortality. The outcomes were reported at various time endpoints, and effect estimates were reported in odd ratios (OR) and 95% confidence intervals (CIs), p-values were calculated, and significance was set at p-value <0.05. 

Results: 
The study cohort included 14,602 patients after propensity-score matching. The Gabapentinoids group (n= 7,301) had 60.4% males and 39.6% females with a mean age of 65.8 years (SD ± 9.6). The No Gabapentinoids group (n=7,301) had 61.1% males and 38.9% females with a mean age of 65.6 years (SD ± 9.7). Primary outcomes showed a significantly increased 5-year risk for opioid-related disorders (5.1% vs 3.4% p<0.001). Logistic regression analysis controlling for 34 covariates and covariables showed statistically significant increase in the 5-year opioid-related disorders risk in patients with history of prescribed gabapentinoids (OR 1.426, CI [1.2, 1.7], p<0.001). Secondary analysis showed a dose-dependent increase in risk of 5-year opioid-related disorders in patients with history of gabapentin (Daily dose mg/day [%risk]: >0-300 mg/day [2.6%], >300-600mg/day [3.7%], >600-1200mg/day [6.3%], >1200-2400mg /day[6.6%], >2400 mg/day [8.4%], p<0.001) and composite 5% compared to 3.4% in the control group (p<0.001).

Conclusion: In patients undergoing lower extremity bypass with a history of prescribed gabapentin, there is an associated increased 5-year risk of opioid-related disorders in dose-dependent fashion. These results underscore the importance of identifying such patients to be at high risk for developing long-term opioid dependence which is associated with higher morbidity and mortality. There is a critical need for effective postoperative pain management planning and the involvement of the patient and other healthcare professionals in coordinating care to mitigate potential risks of opioid-related disorders. This study utilized population-level dataset that included electronic health records and claims data for patients covered with 99% of U.S. health plans which obviates the inherent biases associated with smaller datasets. Findings may not generalize worldwide as the study included only US patients.

History of Gabapentin Predisposes Patients to Risk of Opioid Use, Abuse and Dependence in Dose-Dependent Fashion

BACKGROUND: Incisional hernia (IH) is a common problem following abdominal wall closure after midline laparotomy. Prophylactic mesh placement has been advocated by many randomized controlled trials (RCTs). This meta-analysis seeks to define what population benefits the most from prophylactic mesh (PM) placement, what is the optimal position of PM (onlay vs. sublay), and what type of mesh is preferred (absorbable vs. non-absorbable). 

METHODS: A search of RCTs under PRISMA guidelines was conducted using keywords: mesh, prevention, laparotomy or abdominal surgery, and incisional hernia. 19 RCTs conducted in adults between 1990-2022 included the development of IH as the primary outcome.   

RESULTS: Pooled analysis of all patient populations found lower IH incidence when PM was used over primary fascial closure (PFC) (OR 2.69 [2.23-3.25]). On subgroup analysis, this trend remained true among patients undergoing AAA, bariatric, elective, & emergency surgeries. Both onlay (superficial to anterior rectus fascia) and sublay (deep to anterior rectus fascia) positions were associated with reduced IH risk when compared to PFC, with onlay mesh insignificantly favored over sublay (OR 0.68 [95% CI 0.39-1.19]). Additionally, both non-absorbable and absorbable mesh types demonstrated IH reduction over PFC, but no existing studies compared one mesh type over another. 

CONCLUSION: Prophylactic mesh closure is associated with a lower risk of incisional hernia after midline laparotomy when compared to primary fascial closure. Further research should examine the benefits of PM in other patient populations, specifically emergency operations with contaminated fields, as well as the utility of different mesh positions and mesh typing.

Prophylactic mesh reduces the risk of incisional hernia following midline laparotomy

Background 
Despite advances in surgical technique, perioperative management, and prophylaxis measures, post-discharge venous thromboembolism (pdVTE) remains a life-threatening complication following resection for pancreatic cancer (PC). While current guidelines recommend up to 28 days of thromboprophylaxis after discharge, it must be balanced with the risks of bleeding complications, and cost to the patient. Currently, prediction models to stratify patients by risk of developing pdVTE are limited in accuracy and therefore rarely used. Our preliminary analysis of five models revealed that simple logistic regression outperforms a range of higher-fidelity tree models and neural network models in stratifying patients by risk of developing pdVTE. We hypothesized this is likely due to the machine’s inability to overcome data bias and skewedness when predicting Low Incidence High Mortality (LIHM) post-operative complications. Our goal therefore, was to overcome this challenge by testing the utility of anomaly detection models (ADMs) in identifying patients at high risk of pdVTE after surgery for PC. 

Methods 
We analyzed data from all patients undergoing pancreatectomy for PC using the American College of Surgeons’ National Surgical Quality Improvement Program database from 2014 - 2021. We trained predictive models using 80% of the dataset and 213 input variables including demographics, clinical, laboratory, cancer and operation-specific variables. An unpenalized Logistic Regression (LR) model was used for baseline comparison. The ADMs deployed included Elliptical Envelope (EE), Isolation Forest (IF) and Local Outlier Factor (LOF). Due its low prevalence, pdVTE was defined as an “outlier” for the ADMs to identify amongst “normal” (non-VTE) patients. Models were tested on a 20% hold out dataset using Area-under-the-curve (AUC) scores. Sensitivity, specificity, negative predictive value and positive predictive value were also calculated and compared. 

Results 
A total of 53757 patients were included. The mean age was 63.6 ± 12.8 years, 50.0% were male, and 21,403 (39.8%) underwent Whipple procedures. A total of 1757 (3.3%) developed a pdVTE. In terms of model performance, IF and EE outperformed the LR in terms of both accuracy (Figure 1) and sensitivity. IF had a sensitivity of 0.60, followed by EE 0.57. LR had a sensitivity of 0.50. 

Conclusion 
ADMs provide superior outlier screening capability compared to traditional prediction models thereby bringing a promising opportunity to build risk stratification for LIHM complications such as pdVTE for patients with pancreatic cancer. 


Can Machine-Driven Anomaly Detection Models Identify Patients at Risk for Post-Discharge Venous Thromboembolism After Pancreatectomy for Pancreas Cancer?

Background: 
In addition to surgery, treatment for extremity soft tissue sarcoma (ESTS) should include radiation therapy (RT) for tumors that are high grade and >5 cm. Whether RT should be given in the neoadjuvant (NAT) versus adjuvant (AT) setting is controversial. The aim of this study was to determine if NAT improved adherence with RT compared to AT.

Methods:
Patients with ESTS diagnosed from 2004 through 2020 were identified in the National Cancer Database. The analytic cohort was restricted to patients with high grade tumors >5 cm in size without nodal or distant metastases who received limb-sparing surgery and RT with R0 margins. A multivariable logistic regression analysis identified factors associated with RT adherence, defined according to current guidelines as a dose of 50 Gy for NAT and a dose of 60 Gy for AT. A multivariable Cox Proportional Hazards model was used to assess overall survival.
Results: A total of 2374 patients were evaluated, with 47.3% undergoing NAT (n=1123) and 52.7% (n=1249) undergoing AT. A greater proportion of patients treated with NAT (86.1%) were compliant with the recommended doses of RT when compared to patients treated with AT (69.4%, p<0.0001). A greater proportion of patients with private insurance (51.8% vs. 46.7%, p=0.027) received NAT, as did a greater proportion of patients at academic medical centers (68.0% vs. 56.6%, p<0.001). On multivariable analysis, patients who received AT were more likely to receive an insufficient dose of RT (OR 3.01 [95% CI 2.30-3.96]) as were those who underwent treatment in the South (OR 1.51 [1.05-2.19]) and the Midwest (OR 1.52 [1.02-2.27]). Neither RT adherence nor radiation sequencing (AT vs. NAT) were independent predictors of overall survival. 

Conclusions: Patients who receive RT in the NAT setting are more likely to complete therapy and receive an optimal dose of RT compared to AT. Demographic disparities in receipt of NAT were observed, highlighting an opportunity to improve treatment in patients with high-risk ESTS.

Preoperative Radiation Therapy Increases Adherence in Patients with High-Risk Extremity Soft Tissue Sarcoma

Background
Short bowel syndrome (SBS) arises secondary to insufficient intestinal length to support complete enteral nutrition, often requiring prolonged dependance on parenteral nutrition and potentially invasive surgical lengthening procedures. Recent advancements in the field have introduced distraction enterogenesis as a potential therapeutic approach for lengthening the intestine in SBS patients. The biomechanics and efficiency of our novel intestinal expansion sleeve (IES) has previously been shown to cause sufficient distraction force to cause intestinal expansion ex vivo. In this current investigation, we aim to evaluate the novel intestinal expansion sleeve (IES) to facilitate distraction enterogenesis. We hypothesize that the IES device can achieve significant bowel lengthening in vivo by promoting distraction enterogenesis.
Methods
The IES was made using a proprietary cylindrical material with helicoid trusses cut to an initial length of 30mm. A Roux-en-Y in the jejunum of 6 rats was performed. The IES was precontracted over a Bucatini noodle and inserted into the isolated roux limb. Post-operatively, rats were examined daily, and weight was recorded. After 4 weeks, the rats were sacrificed, final weight was recorded, and the intestines were examined. A paired t-test was performed to compare change in roux limb lengths as well as change in weight post-operatively. Intestinal tissue was sampled from each specimen for histological examination.
Results
Intestinal distraction was evaluated at 4 weeks post deployment of the IES. Use of the IES resulted in a significant increase in roux limb length from an average of 42.5±15mm to 54.2±21.8 mm (p=.043, n=6). Additionally, average final weight was increased following implantation of the IES, although not significant. Average initial weight was 649.2±75.2 grams and final weight was 657.2±86.1 grams (p=0.15). Furthermore, all 6 rats had no post-operative complications because of surgical implantation.
Conclusion
Distraction enterogenesis with significant intestinal lengthening in vivo has been achieved with the IES. Surgical insertion of the IES did not lead to a reduction in rat weight, indicating that the rats tolerated the procedure. Additionally, the IES did not give rise to any complications, such as bowel obstruction. Increasing intestinal mass with these devices may change the treatment paradigm for SBS.

Preliminary Results of a Novel Intestinal Expansion Sleeve on Promoting
Distraction Enterogenesis

Background: Endoscopy is commonly used to diagnose upper gastrointestinal (GI) system disorders. However, excess mucus can significantly impair visualization, and reducing mucus intra-procedurally can increase procedure time. Several studies have evaluated the efficacy of pre-medication with mucolytic agents prior to gastroscopy to improve the diagnostic yield of endoscopy and reduce procedural time. Here, we systematically review recent evidence assessing the efficacy of mucolytic agents, including N-acetyl cysteine (NAC), in improving visibility in upper GI endoscopy.
Methods: Studies were identified by interrogating the PubMed database using the search terms "endoscopy" and "N-acetyl cysteine" for the period of 2016-2023. Only randomized control trials were included in the search. Records written in languages other than English were excluded. Ten (10) records matching these criteria were retrieved. Title and abstract screening resulted in five (5) records, which were subsequently extracted.
Results: The studies were conducted in the United Kingdom, Chile, Portugal, Thailand, and the Czech Republic. Four (4) studies consisted of randomized, double-blinded, placebo-controlled trials, while the remaining study was a randomized, non-blinded controlled trial. Four (4) of the studies showed that pre-administration of NAC (600 mg) plus simethicone (100 mg) significantly improved the visibility of the upper GI tract (esophagus, stomach, and duodenum) when compared to placebo control. The only study that failed to show an improvement in visibility scores was attributed to sub-threshold doses of NAC (400 mg) and simethicone (20 mg). Although none of the studies included an arm consisting of NAC alone, one study comparing simethicone +/- NAC showed superior visibility when NAC was administered at a high dose (1000 mg), while another study comparing simethicone +/- NAC failed to show improvement when NAC was administered at a moderate dose (600 mg). Lastly, one study found that the procedure time and volume of mucosal cleansing solution required were significantly reduced when NAC and simethicone were administered together.


Conclusion: Our survey of recent randomized control trials supports that pre-medication with NAC (600-1000 mg) and simethicone (100 mg) significantly improves the visibility of the upper GI mucosal surfaces during upper endoscopic procedures and, therefore, may improve diagnostic yield in settings where visibility is impaired. This approach may be particularly useful in lower-resource settings where less sophisticated endoscopic tools are utilized.

Efficacy of N-Acetyl Cysteine in the Prevention of Post-Operative Atrial Fibrillation and Acute Kidney Injury Post-Cardiac Surgery: A Systematic Review

Background: Osteosarcoma is the most common primary bone tumor in children and adolescents. Prognostic biomarkers are limited, and post-treatment surveillance relies heavily on radiologic imaging. Capture and analysis of cell-free DNA (cfDNA) from the bloodstream is an emerging technique that could be used to provide additional prognostic information and track residual disease following treatment. 5-hydroxymethylcytosine (5-hmC) is an epigenetic marker of open chromatin and active gene expression, and tumor specific patterns of global 5-hmC deposition are identifiable in several cancers and vary according to disease burden. We profiled 5-hmC using plasma-derived cfDNA from osteosarcoma patients and healthy children to assess its utility as a biomarker of disease status. 

Methods: cfDNA was isolated from patients diagnosed with osteosarcoma and well child controls. Nano-hmC-Seal, a technique developed to isolate 5-hmC-modified DNA fragments, was used to generate sequencing libraries of cfDNA. Genomic DNA from osteosarcoma cell lines was serially diluted with healthy donor-derived cfDNA. DESeq2 was used to identify genes with high 5-hmC deposition in osteosarcoma cell line DNA relative to serial dilutions. In patient cfDNA samples, the relative abundance of 5-hmC deposition on these osteosarcoma genes was determined using gene set variation analysis (GSVA). GSVA returns a score ranging from -1 to 1, with positive values indicating a relative abundance of 5-hmC deposition on osteosarcoma genes.

Results: The cohort consisted of 33 healthy children and 17 patients with osteosarcoma including 53 serially collected samples from these patients. 139 osteosarcoma genes were identified and used for GSVA analysis. Patients with osteosarcoma had significantly higher GSVA scores than well children (0.26 vs -0.38; p<0.001). Hierarchal clustering identified two clusters of samples from children with osteosarcoma. Cluster 1 contained samples with scores correlating with osteosarcoma-derived DNA compared to Cluster 2 (0.14 vs -0.18; p<0.001). Furthermore, Cluster 1 contained 17 of 23 samples from patients with active disease on clinical imaging (sensitivity = 74%, specificity = 57%). High 5-hmC deposition on MYC was readily identified in one sample obtained at diagnosis from the only patient with a MYC amplified tumor. Additional samples from this patient during treatment showed decreasing 5-hmC deposition on MYC, consistent with a treated tumor shedding less DNA into the blood. Additionally, decreased disease burden following surgical resection was identifiable in 5-hmC profiles (presurgical GSVA score 0.22 vs postsurgical -0.08; p=0.004). 

Conclusions: Osteosarcoma 5-hmC signatures can identify patients with active disease. Monitoring cfDNA in osteosarcoma using 5-hmC profiling is a promising technique that warrants further investigation with larger patient cohorts.

Identifying osteosarcoma signatures in cell free DNA using 5-hydroxymethylcytosine profiling

Neuropilin 2 (NRP2) expression in tissue is an independent prognostic factor for aggressive prostate cancer. To investigate if this biomarker is also prognostic when measured using a less invasive sampling method, NRP2 and its ligand, vascular endothelial growth factor C (VEGF-C), were quantified using enzyme-linked immunoassay in 145 prostate cancer patient plasma samples and 15 controls from an opportunistic biobank. Statistical analysis investigated NRP2 and VEGF-C level associations with disease progression, tumor stage, Gleason score, and prostate-specific antigen (PSA). Plasma NRP2 was not associated with more aggressive disease, in contrast to what has been shown in tissue. Increased plasma VEGF-C was associated with less severe disease, including remission, Stage I/II, and intermediate-risk Gleason score. Further studies are needed to identify non-invasive methods to assess NRP2 status.

Association of plasma NRP2 and VEGF-C levels with prostate cancer disease severity

Rare Presentation of HPV-related Retroperitoneal Squamous Cell Carcinoma of Unknown Primary: A case report

Background
Both hepatocellular cancer and liver metastases are associated with poor clinical outcome and limited therapeutic response to immunotherapy. Tumor antigen specific CD8 T cells in the liver have been studied in the setting of both immunotherapy and cellular therapy with the predominant dogma that these cells have equivalent functionality in the liver as compared to other organ sites. Herein, we detail that tumor antigen specific or potentially tumor reactive CD 8 T cells are uniquely nonfunctional in the liver immune microenvironment in both mice and humans. 
Methods
Both a colon cancer line (CT26) and a melanoma model (B16F10) were injected intrahepatically, into the tail vein, and subcutaneously in BALB/c and C57BL/6 mice to create liver, pulmonary and subcutaneous tumors respectively. CD8 T cells were depleted by ⍺CD8 treatment. Liver and tumor infiltrating immune cells and splenocytes were analyzed by flow cytometry. Peptide loaded tetramers were used to identify antigen-specific T cells and tumor growth was monitored. Additionally, publically available single cell RNA sequencing data from 10 patient samples with primary colon cancer and liver metastasis were used. Human single cell data was analyzed using the Seurat pipeline and single cell gene enrichment analysis in R. 
Results
Both in mice and humans, a higher frequency of tumor antigen specific or potentially tumor reactive CD8 T cells was found in the liver as compared to other organ sites. Additionally, a higher frequency of these were found to be exhausted in the liver (TIM3+ and CD39+ in mice and an exhausted cluster similarly defined in humans). Surprisingly, CD8 T cell depletion had no effect on tumor growth in the liver while depletion caused tumor growth in the subcutaneous model. Additionally, through Cell Chat analysis, SPP1 positive macrophages were found to be key mediators of this exhausted phenotype and these interactions were enriched in the liver. 
Conclusion
Tumor reactive CD8 T cells are found at significantly higher frequency in the liver. Despite the higher frequency of “killer” T cells in the liver, tumor growth in the liver was not impacted by tumor reactive CD8 T cells in contrast to subcutaneous tumors, which were smaller in the presence of tumor-specific T cells. Spp1+ macrophages seem to be key mediators in tumor reactive CD8 T cell dysfunction uniquely in the liver. These findings may explain the poor clinical response seen in these patients as well as present as a potentially target for therapeutic affects.

Next from AMA Research Challenge 2023

History of Gabapentin Predisposes Patients to Risk of Opioid Use, Abuse and Dependence in Dose-Dependent Fashion