A common secretomic signature across epithelial cancers metastatic to the pleura supports IL-6 axis therapeutic targeting.

Background: Many cancers metastasize to the pleura, resulting in effusions that cause dyspnea and discomfort. Regardless of the tissue of origin, pleural malignancies are aggressive and uniformly fatal, with no treatment shown to prolong life. The pleural mesothelial monolayer is joined by tight junctions forming a contained bioreactor-like space, concentrating cytokines and chemokines secreted by the mesothelium, tumor, and infiltrating immune cells. This space represents a unique environment that profoundly influences tumor and immune cell behavior. Defining the pleural secretome is an important step in the rational development localized intrapleural immunotherapy. Method: We measured cytokine/chemokine content of 252 malignant pleural effusion (MPE) samples across multiple cancers using a 40-analyte panel and Luminex multiplexing technology. Results: Eleven analytes were consistently present in concentrations ≥ 10.0 pM: CXCL10/IP10 (geometric mean = 672.3 pM), CCL2/MCP1 (562.9 pM), sIL-6Rα (403.1 pM), IL-6 (137.6 pM), CXCL1/GRO (80.3 pM), TGFß1 (76.8 pM), CCL22/MDC (54.8 pM), CXCL8/IL-8 (29.2 pM), CCL11/Eotaxin (12.6 pM), IL-10 (11.3 pM), and G-CSF (11.0 pM). All are capable of mediating chemotaxis, promotion of epithelial to mesenchymal transition, or immunosuppression, and many of are reportedly downstream of a pro-inflammatory cytokine cascade mediated by cytokine IL-6 and its soluble receptor. Conclusion: The data indicate high concentrations of several cytokines and chemokines across epithelial cancers metastatic to the pleura and support the contention that the pleural environment is the major factor responsible for the clinical course of MPE across cancer types. A sIL-6Rα to IL-6 molar ratio of 2.7 ensures that virtually all epithelial, immune and vascular endothelial cells in the pleural environment are affected by IL-6 signaling. The central role likely played by IL-6 in the pathogenesis of MPE argues in favor of a therapeutic approach targeting the IL-6/IL-6R axis.

Gastrointestinal Permeability After Bariatric Surgery: A Systematic Review.

Gastrointestinal permeability refers to the movement of substances across the gut wall. This is mediated by endotoxemia (bacterial products entering the systemic circulation), and is associated with metabolic disease. The effect of bariatric surgery on permeability remains uncertain; the associated dietary, metabolic and weight changes are suggested to influence, or trigger, altered permeability. The primary aim of this study is to synthesize evidence and analyze the effect of bariatric surgery on permeability. A systematic review was performed, searching MEDLINE, EMBASE, and Scopus until February 2023, using MESH terms "intestinal permeability", "bariatric", for studies reporting in vivo assessment of permeability. Three cohort studies and two case series were identified (n=96). Data was heterogeneous; methodology and controls preclude meta-analysis. Gastroduodenal permeability reduced post-sleeve gastrectomy (SG). Two studies showed an increase in small intestinal permeability after biliopancreatic diversion. Two studies revealed a decrease in post-Roux-en-Y gastric bypass. One study identified increased colonic permeability six months post-SG. Evidence regarding permeability change after bariatric surgery is conflicting, notably for the small intestine. Impaired colonic permeability post-SG raises concerns regarding colonic protein fermentation and harmful dietary sequelae. There are multiple interacting variables confounding gastrointestinal permeability change; procedure type, altered microbiota and metabolic response to surgery. Further understanding of this important aspect of obesity is required, both before and after bariatric surgery.

Hepatobiliary Infection after Transjugular Intrahepatic Portosystemic Shunt Creation in Patients with Prior Biliary Intervention: A Multi-Institution Retrospective Study.

PURPOSE: To estimate the risk of hepatobiliary infection, including endoTIPSitis, liver abscesses, and cholangitis, after transjugular intrahepatic portosystemic shunt (TIPS) creation in patients with prior biliary intervention. MATERIALS AND METHODS: This multi-institution, retrospective study identified 76 patients (n = 48 males; mean age, 54.9 years; mean Model for End-stage Liver Disease [MELD] score, 13.2; n = 45 for ascites and n = 23 for varices; n = 31 with prior liver transplantation) among 2,130 (3.6%) undergoing TIPS creation who had prior biliary intervention (n = 19 bilioenteric anastomoses, n = 35 sphincterotomies, n = 28 internal plastic stent placements, n = 4 internal metal stent placements, and n = 6 percutaneous biliary drain placements). The baseline risk of post-TIPS creation hepatobiliary infection was estimated from a control group of 1,202 TIPS creation procedures in patients without prior biliary intervention. RESULTS: Eleven (14.5%) of 76 patients developed hepatobiliary infection after TIPS creation, including 7 with endoTIPSitis, 4 with hepatic abscesses, and 2 with cholangitis. The 30-day risk of infection was 10.9% (95% confidence interval [CI], 3.5%-17.8%), significantly higher than the 0.4% risk (95% CI, 0.1%-0.8%) observed in patients without prior biliary intervention (hazard ratio [HR], 25.56; 95% CI, 8.36-78.13; P < .001). All types of biliary intervention were associated with increased risk of infection, with bilioenteric anastomoses conferring the highest risk. Paradoxically, among patients with prior biliary intervention, use of postprocedural antibiotic prophylaxis was associated with an increased infection risk (HR, 19.85; 95% CI, 2.44-161.50; P = .005). Microbial culture data showed high rates of Enterococcus, Klebsiella, and Candida species. CONCLUSIONS: Prior biliary intervention was associated with a 10.9% risk of hepatobiliary infection, including endoTIPSitis, liver abscess, and cholangitis, within 30 days after TIPS creation.

Microsatellite instability should not determine candidacy for cytoreductive surgery and hyperthermic intraperitoneal chemoperfusion in patients with peritoneal metastases from colorectal cancer.

BACKGROUND: Cytoreductive surgery (CRS) plus hyperthermic intraperitoneal chemotherapy (HIPEC) is a multimodal therapeutic option for the management of peritoneal metastases (PM). Treatment outcomes for patients with colorectal cancer (CRC) PM undergoing CRS+HIPEC with microsatellite instability (MSI) remain unknown. We examined the patient characteristics and outcomes in patients with MSI CRC after CRS+HIPEC. METHODS: This was a retrospective cohort study of a prospectively maintained database of all patients with CRC PM undergoing CRS+HIPEC (2010-2020). Categorical and continuous variables were analyzed using the chi-square test and independent samples t test, respectively. Survival was evaluated with the Kaplan-Meier analysis. RESULTS: There were 324 patients diagnosed as having CRC PM undergoing CRS+HIPEC (MSI, n = 23; microsatellite stable [MSS], n = 301). There was no statistically significant difference in patient demographics, tumor characteristics, or perioperative factors between the 2 groups. There was a trend toward improved survival in the MSI group with a median overall survival (OS) of 96.7 month compared with patients with MSS disease (median OS, 51.4 months; P = .10). Patients with MSI demonstrated median progression-free survival (PFS) 8.5 months compared with 11.4 months in the MSS cohort (P = .28). CONCLUSION: Patients with CRC PM, regardless of MSI or MSS status, demonstrate similar OS and PFS after CRS+HIPEC. MSI status should not change a patient's candidacy for CRS+HIPEC.

Meta-analysis of survival after pulmonary resection for isolated metachronous pancreatic cancer metastasis: a promising, albeit infrequent, approach.

BACKGROUND: To evaluate survival outcomes of pulmonary resection for isolated metachronous pancreatic cancer metastasis. METHODS: A systematic search of electronic data sources and reference lists were conducted. Proportion meta-analysis model was constructed to quantify 1- to 5-year survival after pulmonary resection for isolated metachronous pancreatic cancer metastasis. Random-effects modelling was applied to calculate pooled outcome data. RESULTS: Twenty-four retrospective studies were included reporting a total of 168 patients who underwent pulmonary resection for isolated pancreatic cancer metastasis. The nature of the index pancreatic surgery included 65% pancreaticoduodenectomies, 17.5% distal pancreatectomies, 0.5% total pancreatectomy, and 17% unspecified. Adjuvant chemotherapy was given to 88% of the patients. The median disease-free interval was 35 (8-96) months. The type of pulmonary resection included 54% wedge resections, 26% lobectomies, 4% segmentectomies, 1% pneumonectomies, and 15% unspecified. Pulmonary resection was associated with 1-year survival of 91.1% (95% CI 86.6%-95.5%), 2-year survival of 77.5% (95% CI 68.9%-86.0%), 3-year survival of 65.0% (95% CI 50.7%-79.3%), 4-year survival of 52.0% (95% CI 37.2%-66.9%), and 5-year survival of 37.0% (95% CI 25.0%-49.1%). CONCLUSION: Pulmonary resection for isolated pancreatic cancer metastasis is associated with acceptable overall patient survival. We recommend selective pulmonary resection for isolated pulmonary metastasis from pancreatic cancer. Our findings may encourage conduction of better-quality studies in this context to help establishment of definitive treatment strategies.

Detection of Residual Peritoneal Metastases Following Cytoreductive Surgery Using Pegsitacianine, a pH-Sensitive Imaging Agent: Final Results from a Phase II Study.

BACKGROUND: For patients with peritoneal carcinomatosis, extent of disease and completeness of cytoreductive surgery (CRS) are major prognostic factors for long-term survival. Assessment of these factors could be improved using imaging agents. Pegsitacianine is a pH-sensitive polymeric micelle conjugated to the fluorophore indocyanine green. The micelle disassembles in acidic microenvironments, such as tumors, resulting in localized fluorescence unmasking. We assessed the utility of pegsitacianine in detecting residual disease following CRS. PATIENTS AND METHODS: NCT04950166 was a phase II, non-randomized, open-label, multicenter US study. Patients eligible for CRS were administered an intravenous dose of pegsitacianine at 1 mg/kg 24-72 h before surgery. Following CRS, the peritoneal cavity was reexamined under near-infrared (NIR) illumination to evaluate for fluorescent tissue. Fluorescent tissue identified was excised and evaluated by histopathology. The primary outcome was the rate of clinically significant events (CSE), defined as detection of histologically confirmed residual disease excised with pegsitacianine or a revision in the assessment of completeness of CRS. Secondary outcomes included acceptable safety and pegsitacianine performance. RESULTS: A total of 53 patients were screened, 50 enrolled, and 40 were evaluable for CSE across six primary tumor types. Residual disease was detected with pegsitacianine in 20 of 40 (50%) patients. Pegsitacianine showed high sensitivity and was well tolerated with no serious adverse events (SAEs). Transient treatment-related, non-anaphylactic infusion reactions occurred in 28% of patients. CONCLUSIONS: Pegsitacianine was well tolerated and facilitated the recognition of occult residual disease following CRS. The high rate of residual disease detected suggests that the use of pegsitacianine augmented surgeon assessment and performance during CRS.

A machine learning approach for predicting textbook outcome after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.

INTRODUCTION: Peritoneal carcinomatosis is considered a late-stage manifestation of neoplastic diseases. Cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC) can be an effective treatment for these patients. However, the procedure is associated with significant morbidity. Our aim was to develop a machine learning model to predict the probability of achieving textbook outcome (TO) after CRS-HIPEC using only preoperatively known variables. METHODS: Adult patients with peritoneal carcinomatosis and who underwent CRS-HIPEC were included from a large, single-center, prospectively maintained dataset (2001-2020). TO was defined as a hospital length of stay ≤14 days and no postoperative adverse events including any complications, reoperation, readmission, and mortality within 90 days. Four models (logistic regression, neural network, random forest, and XGBoost) were trained, validated, and a user-friendly risk calculator was then developed. RESULTS: A total of 1954 CRS-HIPEC procedures for peritoneal carcinomatosis were included. Overall, 13% (n = 258) achieved TO following CRS-HIPEC procedure. XGBoost and logistic regression had the highest area under the curve (AUC) (0.76) after model optimization, followed by random forest (AUC 0.75) and neural network (AUC 0.74). The top preoperative variables associated with achieving a TO were lower peritoneal cancer index scores, not undergoing proctectomy, splenectomy, or partial colectomy and being asymptomatic from peritoneal metastases prior to surgery. CONCLUSION: This is a data-driven study to predict the probability of achieving TO after CRS-HIPEC. The proposed pipeline has the potential to not only identify patients for whom surgery is not associated with prohibitive risk, but also aid surgeons in communicating this risk to patients.

Targeting interleukin-6 as a treatment approach for peritoneal carcinomatosis.

Peritoneal carcinomatosis (PC) is a complex manifestation of abdominal cancers, with a poor prognosis and limited treatment options. Recent work identifying high concentrations of the cytokine interleukin-6 (IL-6) and its soluble receptor (sIL-6-Rα) in the peritoneal cavity of patients with PC has highlighted this pathway as an emerging potential therapeutic target. This review article provides a comprehensive overview of the current understanding of the potential role of IL-6 in the development and progression of PC. We discuss mechansims by which the IL-6 pathway may contribute to peritoneal tumor dissemination, mesothelial adhesion and invasion, stromal invasion and proliferation, and immune response modulation. Finally, we review the prospects for targeting the IL-6 pathway in the treatment of PC, focusing on common sites of origin, including ovarian, gastric, pancreatic, colorectal and appendiceal cancer, and mesothelioma.

Marker selection strategies for circulating tumor DNA guided by phylogenetic inference.

Motivation: Blood-based profiling of tumor DNA ("liquid biopsy") has offered great prospects for non-invasive early cancer diagnosis, treatment monitoring, and clinical guidance, but require further advances in computational methods to become a robust quantitative assay of tumor clonal evolution. We propose new methods to better characterize tumor clonal dynamics from circulating tumor DNA (ctDNA), through application to two specific questions: 1) How to apply longitudinal ctDNA data to refine phylogeny models of clonal evolution, and 2) how to quantify changes in clonal frequencies that may be indicative of treatment response or tumor progression. We pose these questions through a probabilistic framework for optimally identifying maximum likelihood markers and applying them to characterizing clonal evolution. Results: We first estimate a distribution over plausible clonal lineage models, using bootstrap samples over pre-treatment tissue-based sequence data. We then refine these lineage models and the clonal frequencies they imply over successive longitudinal samples. We use the resulting framework for modeling and refining tree distributions to pose a set of optimization problems to select ctDNA markers to maximize measures of utility capturing ability to solve the two questions of reducing uncertain in phylogeny models or quantifying clonal frequencies given the models. We tested our methods on synthetic data and showed them to be effective at refining distributions of tree models and clonal frequencies so as to minimize measures of tree distance relative to the ground truth. Application of the tree refinement methods to real tumor data further demonstrated their effectiveness in refining a clonal lineage model and assessing its clonal frequencies. The work shows the power of computational methods to improve marker selection, clonal lineage reconstruction, and clonal dynamics profiling for more precise and quantitative assays of tumor progression. Availability: https://github.com/CMUSchwartzLab/Mase-phi.git. Contact: russells@andrew.cmu.edu.

Assessing the long-term priorities of pancreaticoduodenectomy survivors.

BACKGROUND: This study assessed the long-term quality of life (QOL) and priorities of pancreaticoduodenectomy (PD) survivors. METHODS: Survivors were surveyed via internet-based support groups. The relative importance of longevity, experience, costs, and QOL were assessed. RESULTS: The PD cohort (n = 247, 35%) was 60 ± 12 years, 71% female, and 93% white. With moderate agreement, patients ranked survival most important, followed by functional and emotional well-being; costs and experience were least important (W = 35.7%, p < 0.001). Well-being improved throughout survivorship (P-QOL: 39 ± 12 at ≤3 mo vs 43 ± 12 at >10 y, p = 0.170; M-QOL: 38 ± 13 at ≤3 mo vs 44 ± 16 at >10 y; p = 0.015) but remained below the general population (p < 0.001). PD patients with benign diagnoses ranked functional independence as most important (2.00 ± 1.13 vs 2.63 ± 1.19, p < 0.001, W = 41.1%); PD patients with malignant diagnoses regarded overall survival most important (2.10 ± 1.20 vs 1.82 ± 1.22, p < 0.16, W = 35.1%). The mean rank order of priorities remained concordant between short-term (<1 year) and long-term (>5 years) survivors. CONCLUSION: PD survivors experience long-term mental and physical health impairments, underscoring the importance of functional and emotional support. Survivors place paramount importance on overall survival, functional independence, and emotional well-being. Cancer survivors prioritize longevity, while survivors of chronic benign conditions prioritize functional independence.

Modeling the Effect of Spatial Structure on Solid Tumor Evolution and Circulating Tumor DNA Composition.

Circulating tumor DNA (ctDNA) monitoring, while sufficiently advanced to reflect tumor evolution in real time and inform cancer diagnosis, treatment, and prognosis, mainly relies on DNA that originates from cell death via apoptosis or necrosis. In solid tumors, chemotherapy and immune infiltration can induce spatially variable rates of cell death, with the potential to bias and distort the clonal composition of ctDNA. Using a stochastic evolutionary model of boundary-driven growth, we study how elevated cell death on the edge of a tumor can simultaneously impact driver mutation accumulation and the representation of tumor clones and mutation detectability in ctDNA. We describe conditions in which invasive clones are over-represented in ctDNA, clonal diversity can appear elevated in the blood, and spatial bias in shedding can inflate subclonal variant allele frequencies (VAFs). Additionally, we find that tumors that are mostly quiescent can display similar biases but are far less detectable, and the extent of perceptible spatial bias strongly depends on sequence detection limits. Overall, we show that spatially structured shedding might cause liquid biopsies to provide highly biased profiles of tumor state. While this may enable more sensitive detection of expanding clones, it could also increase the risk of targeting a subclonal variant for treatment. Our results indicate that the effects and clinical consequences of spatially variable cell death on ctDNA composition present an important area for future work.

Intratumoral Delivery of Interleukin 9 via Oncolytic Vaccinia Virus Elicits Potent Antitumor Effects in Tumor Models.

The success of cancer immunotherapy is largely associated with immunologically hot tumors. Approaches that promote the infiltration of immune cells into tumor beds are urgently needed to transform cold tumors into hot tumors. Oncolytic viruses can transform the tumor microenvironment (TME), resulting in immunologically hot tumors. Cytokines are good candidates for arming oncolytic viruses to enhance their function in this transformation. Here, we used the oncolytic vaccinia virus (oVV) to deliver interleukin-9 (IL-9) into the tumor bed and explored its antitumor effects in colon and lung tumor models. Our data show that IL-9 prolongs viral persistence, which is probably mediated by the up-regulation of IL-10. The vvDD-IL-9 treatment elevated the expression of Th1 chemokines and antitumor factors such as IFN-γ, granzyme B, and perforin. IL-9 expression increased the percentages of CD4+ and CD8+ T cells in the TME and decreased the percentage of oVV-induced immune suppressive myeloid-derived suppressor cells (MDSC), leading to potent antitumor effects compared with parental virus treatment. The vvDD-IL-9 treatment also increased the percentage of regulatory T cells (Tregs) in the TME and elevated the expression of immune checkpoint molecules such as PD-1, PD-L1, and CTLA-4, but not GITR. The combination therapy of vvDD-IL-9 and the anti-CTLA-4 antibody, but not the anti-GITR antibody, induced systemic tumor-specific antitumor immunity and significantly extended the overall survival of mice, indicating a potential translation of the IL-9-expressing oncolytic virus into a clinical trial to enhance the antitumor effects elicited by an immune checkpoint blockade for cancer immunotherapy.

Frequency of Locator Legacy Insert Changes With Implant Overdentures in a UK Population.

PURPOSE: To determine the frequency of insert changes for combined maxillary and mandibular implant overdentures (IOD) using the Locator Legacy system. A secondary objective was to assess the survival of dental implants with IODs. MATERIALS AND METHODS: This retrospective audit reviewed clinical records with up to 12 years follow up from 785 patients who received IODs using the Locator system at a dental hospital. From these, 151 had a combined maxillary opposed by a mandibular IOD and from this, 37 had data retrieved using a minimum data set. The frequency of insert change was recorded and descriptive analysis was provided by means and standard deviations for continuous variables. Frequencies of categorical values were reported as percentages. RESULTS: 222 implants were placed on 21 men, 16 women with a mean age 67.5 years (SD 8.8). All patients were reviewed at least once. Maxillary and mandibular IODs experienced 1.9 (SD 2.0) and 1.2 (SD 1.2) mean insert changes per patient, respectively. The mean time (SD) between initial and first insert change for maxillary and mandibular IODs was 3.4 months (SD 3.2) and 6.4 months (SD 7.2) and between the first and second insert change was 9.9 months (SD 9.0) and 10.0 months (SD 8.3), respectively. Implant failure was 21.6% and 2.7% in the maxilla and mandible respectively. CONCLUSIONS: Clinicians should anticipate the first insert change around 3 months for maxillary IOD and 6 months for mandibular IOD. Subsequently, the second insert change to be around 10 months for both maxillary and mandibular IODs.

Comprehensive value implications of surgeon volume for lung cancer surgery: Use of an analytic framework within a regional health system.

Objective: We used a framework to assess the value implications of thoracic surgeon operative volume within an 8-hospital health system. Methods: Surgical cases for non-small cell lung cancer were assessed from March 2015 to March 2021. High-volume (HV) surgeons performed >25 pulmonary resections annually. Metrics include length of stay, infection rates, 30-day readmission, in-hospital mortality, median 30-day charges and direct costs, and 3-year recurrence-free and overall survival. Multivariate regression-based propensity scores matched patients between groups. Metrics were graphed on radar charts to conceptualize total value. Results: All 638 lung resections were performed by 12 surgeons across 6 hospitals. Two HV surgeons performed 51% (n = 324) of operations, and 10 low-volume surgeons performed 49% (n = 314). Median follow-up was 28.8 months (14.0-42.3 months). Lobectomy was performed in 71% (n = 450) of cases. HV surgeons performed more segmentectomies (33% [n = 107] vs 3% [n = 8]; P < .001). Patients of HV surgeons had a lower length of stay (3 [2-4] vs 5 [3-7]; P < .001) and infection rates (0.6% [n = 1] vs 4% [n = 7]; P = .03). Low-volume and HV surgeons had similar 30-day readmission rates (14% [n = 23] vs 7% [n = 12]; P = .12), in-hospital mortality (0% [n = 0] vs 0.6% [n = 1]; P = .33), and oncologic outcomes; 3-year recurrence-free survival was 95% versus 91%; P = .44, and 3-year overall survival was 94% versus 90%; P = 0. Charges were reduced by 28%, and direct costs were reduced by 23% (both P < .001) in the HV cohort. Conclusions: HV surgeons provide comprehensive value across a health system. This multidomain framework can be used to help drive oncologic care decisions within a health system.

Can preoperative Carbohydrate Antigen 19-9 predict metastatic pancreatic cancer? Results of a systematic review and meta-analysis.

BACKGROUND: To investigate the relationship between preoperative Carbohydrate Antigen19-9(CA19-9)and pancreatic cancer occult metastasis. METHODS: Systematic search of MEDLINE, CENTRAL, Web of Science and bibliographic reference lists were conducted. All comparative observational studies investigating the predictive ability of preoperative CA 19-9 in patients with pancreatic cancer were considered. Mean CA-19-9 value in the pancreatic cancer patients with and without metastasis were evaluated. Best cut-off value of CA 19-9 for metastasis was determined using ROC analysis. RESULTS: Ten comparative observational studies reporting a total of 1431 pancreatic cancer patients with (n = 496) and without (n = 935) metastasis were included. Subsequent meta-analysis demonstrated that mean preoperative CA 19-9 level was significantly higher in patients with metastases compared to those without (MD: 904.4; 95 % CI, 642.08-1166.74, P < 0.0001). The between-study heterogeneity was significant (I2: 99 %, P < 0.00001). ROC analysis yielded a cut-off CA 19-9 level of 336 with a sensitivity and specificity for predicting metastasis of 90 % and 80 %, respectively (AUC = 0.90). CONCLUSIONS: CA 19-9 level is significantly higher in patients with metastatic pancreatic cancer. A preoperative CA 19-9 value of 336 should be considered as an acceptable cut-off value to design prospective studies.

Pilot clinical study to evaluate the efficacy of a professionally delivered high fluoride varnish on erosive tooth wear in an in-situ model.

OBJECTIVES: The aim for this pilot study was to investigate the effect of a sodium fluoride varnish on step height measured by a profilometer from human enamel worn by healthy volunteers with a novel in situ/ex vivo erosion design. METHOD: Healthy volunteers aged 18-70 years wore a palatal splint containing 8 human enamel samples and underwent two 3-day treatment periods for 6 h a day with a varnish containing sodium fluoride at 22,600 ppm and the control with the same ingredients but without fluoride. Each splint contained 4 polished and 4 unpolished samples. The interventions were applied to the surface of the enamel samples in randomised order, removed after 6 h, then immersed ex-vivo in 1 %, pH 2.7 citric acid for 2 min, repeated 4 times a day, over 2 days. Measurements of enamel were assessed blindly by microhardness on day 2 and by non-contact laser profilometry on day 3 for the two treatments. RESULTS: 24 volunteers, 2 males and 22 females aged 27-54 years, were screened and recruited. The delta microhardness, from polished samples removed at the end of day 2, for the control and fluoride treatment was 95.7 (22.9) kgf/mm2 and 123.7 (28.9) kgf/mm2, respectively (p < .005). The mean (SD) step height for the control polished enamel surfaces was 3.67 (2.07) µm and for the fluoride varnish was 1.79 (1.01) µm (p < .0005). The control unpolished enamel surfaces had a mean 2.09 (1.53) µm and the fluoride varnish was 2.11 (1.53) µm but no statistical difference was detected. CONCLUSIONS: The results from this pilot study, utilizing an in-situ model where enamel was exposed to acid over the course of 2 days, demonstrated that a high fluoride varnish containing sodium fluoride at 22,600 ppm prevented erosive wear compared to a control on the polished enamel surfaces. CLINICAL SIGNIFICANCE: Intra-oral study demonstrated that a high fluoride varnish containing sodium fluoride at 22,600 ppm reduced erosive tooth wear.