Overall Volume of Upper Gastrointestinal Surgery Positively Impacts Gastric Cancer Outcomes at Centers with Low Gastrectomy Volume.

BACKGROUND: The relationship between hospital volume and surgical mortality is well documented. However, complete centralization of surgical care is not always feasible. The present study investigates how overall volume of upper gastrointestinal surgery at hospitals influences patient outcomes following resection for gastric adenocarcinoma. PATIENTS AND METHODS: National Cancer Database (2010-2019) patients with pathologic stage 1-3 gastric adenocarcinoma who underwent gastrectomy were identified. Three cohorts were created: low-volume hospitals (LVH) for both gastrectomy and overall upper gastrointestinal operations, mixed-volume hospital (MVH) for low-volume gastrectomy but high-volume overall upper gastrointestinal operations, and high-volume gastrectomy hospitals (HVH). Chi-squared tests were used to analyze sociodemographic factors and surgical outcomes and Kaplan-Meier method for survival analysis. RESULTS: In total, 26,398 patients were identified (LVH: 20,099; MVH: 539; HVH: 5,760). The 5-year survival was equivalent between MVH and HVH for all stages of disease (MVH: 56.0%, HVH 55.6%; p = 0.9866) and when stratified into early (MVH: 69.9%, HVH: 65.4%; p = 0.1998) and late stages (MVH: 24.7%, HVH: 32.0%; p = 0.1480), while LVH had worse survival. After matching patients, postoperative outcomes were worse for LVH, but there was no difference between MVH and HVH in terms of adequate lymphadenectomy, margin status, readmission rates, and 90-day mortality rates. CONCLUSIONS: Despite lower gastrectomy volume for cancer, postoperative gastrectomy outcomes at centers that perform a high number of upper gastrointestinal cancer surgeries were similar to hospitals with high gastrectomy volume. These hospitals offer a blueprint for providing equivalent outcomes to high volume centers while enhancing availability of quality cancer care.

Trends in access to minimally invasive pancreaticoduodenectomy for pancreatic cancers.

BACKGROUND: Minimally invasive pancreaticoduodenectomy (MIPD), including robotic (RPD) and laparoscopy (LPD), is becoming more frequently employed in the management of pancreatic ductal adenocarcinoma (PDAC), though the majority of operations are still performed via open approach (OPD). Access to technologic advances often neglect the underserved. Whether disparities in access to MIPD exist, remain unclear. METHODS: The National Cancer Database (NCDB) was queried (2010-2020) for patients who underwent pancreatoduodenectomy for PDAC. Cochran-Armitage tests assessed for trends over time. Social determinants of health (SDH) were compared between approaches. Multinomial logistic models identified predictors of MIPD. RESULTS: Of 16,468 patients, 80.03 % underwent OPD and 19.97 % underwent MIPD (22.60 % robotic; 77.40 % laparoscopic). Black race negatively predicted LPD (vs white (OR 0.822; 95 % CI 0.701-0.964)). Predictors of RPD included Medicare/other government insurance (vs uninsured or Medicaid (OR 1.660; 95 % CI 1.123-2.454)) and private insurance (vs uninsured or Medicaid (OR 1.597; 95 % CI 1.090-2.340)). Early (2010-2014) vs late (2015-2020) diagnosis, stratified by race, demonstrated an increase in Non-White patients undergoing OPD (13.15 % vs 14.63 %; p = 0.016), but not LPD (11.41 % vs 13.57 %;p = 0.125) or RPD (14.15 % vs 15.23 %; p = 0.774). CONCLUSION: SDH predict surgical approach more than clinical stage, facility type, or comorbidity status. Disparities in race and insurance coverage are different between surgical approaches.

Socioeconomic Mediation of Racial Segregation in Pancreatic Cancer Treatment and Outcome Disparities.

OBJECTIVE: To understand the mediating effect of socioeconomic factors on the association between residential segregation and racial disparities in pancreatic cancer (PC). BACKGROUND: Black patients with PC present at a later stage and have worse mortality than White patients. These disparities have been explained by the level of residential segregation. METHODS: Data were obtained from Surveillance, Epidemiology, and End-Results (SEER) and included all Black and White patients who were diagnosed with PC between 2005 and 2015. The primary exposure variable was the Index of Dissimilarity, a validated measure of segregation. County-level socioeconomic variables from the US Census were assessed as mediators. The primary outcomes were advanced stage at diagnosis, surgical resection for localized disease, and overall mortality. Generalized structural equation modeling was used to assess the mediation of each of the socioeconomic variables. RESULTS: Black patients in the highest levels of segregation saw a 12% increased risk [relative risk=1.12; 95% confidence interval (CI): 1.08, 1.15] of presenting at an advanced stage, 11% decreased likelihood of undergoing surgery (relative risk=0.89; 95% CI: 0.83, 0.94), and 8% increased hazards of death (hazard ratio=1.08; 95% CI: 1.03, 1.14) compared with White patients in the lowest levels. The Black share of the population, insurance status, and income inequality mediated 58% of the total effect on the advanced stage. Poverty and Black income immobility mediated 51% of the total effect on surgical resection. Poverty and Black income immobility mediated 50% of the total effect on overall survival. CONCLUSIONS: These socioeconomic factors serve as intervention points for legislators to address the social determinants inherent to the structural racism that mediate poor outcomes for Black patients.

The Persistence of Poverty and its Impact on Cancer Diagnosis, Treatment and Survival.

OBJECTIVE: To determine the effect of persistent poverty on the diagnosis, surgical resection and survival of patients with non-small cell lung (NSCLC), breast, and colorectal cancer. BACKGROUND: Disparities in cancer outcomes exist in counties with high levels of poverty, defined as ≥20% of residents below the federal poverty level. Despite this well-established association, little is known about how the duration of poverty impacts cancer care and outcomes. One measure of poverty duration is that of "persistent poverty," defined as counties in high poverty since 1980. METHODS: In this retrospective cohort study, patients with NSCLC, breast and colorectal cancer were identified from SEER (2012-2016). County-level poverty was obtained from the American Community Survey (1980-2015). Outcomes included advanced stage at diagnosis (stage III-IV), resection of localized disease (stage I-II) and cancer-specific survival. Hierarchical generalized linear models and accelerated failure time models with Weibull distribution were used, adjusted for patient-level covariates and region. RESULTS: Overall, 522,514 patients were identified, of which 5.1% were in persistent poverty. Patients in persistent poverty were more likely to present with advanced disease [NSCLC odds ratio (OR): 1.12, 95% confidence interval (CI): 1.06-1.18; breast OR: 1.09, 95% CI: 1.02-1.17; colorectal OR: 1.00, 95% CI: 0.94-1.06], less likely to undergo surgery (NSCLC OR: 0.81, 95% CI: 0.73-0.90; breast OR: 0.82, 95% CI: 0.72-0.94; colorectal OR: 0.84, 95% CI: 0.70-1.00) and had increased cancer-specific mortality (NSCLC HR: 1.09, 95% CI: 1.06-1.13; breast HR: 1.18, 95% CI: 1.05-1.32; colorectal HR: 1.09, 95% CI: 1.03-1.17) as compared with those without poverty. These differences were observed to a lesser magnitude in counties with current, but not persistent, poverty and disappeared in counties no longer in poverty. CONCLUSIONS: The duration of poverty has a direct impact on cancer-specific outcomes, with the greatest effect seen in persistent poverty and resolution of disparities when a county is no longer in poverty. Policy focused on directing resources to communities in persistent poverty may represent a possible strategy to reduce disparities in cancer care and outcomes.

Combined High-Volume Common Complex Cancer Operations Safeguard Long-Term Survival in a Low-Volume Individual Cancer Operation Setting.

BACKGROUND: We previously demonstrated the importance of combined complex surgery volume on short-term outcomes of high-risk cancer operations. This study investigates the impact of combined common complex cancer operation volume on long-term outcomes at hospitals with low cancer-specific operation volumes. PATIENTS AND METHODS: A retrospective cohort of National Cancer Data Base (2004-2019) patients undergoing surgery for hepatocellular carcinoma, non-small cell lung cancers, or pancreatic, gastric, esophageal, or rectal adenocarcinomas was utilized. Three separate cohorts were established: low-volume hospitals (LVH), mixed-volume hospitals (MVH) with low-volume individual cancer operations and high-volume total complex operations, and high-volume hospitals (HVH). Survival analyses were performed for overall, early-, and late-stage disease. RESULTS: The 5 year survival was significantly better at MVH and HVH compared with LVH, for all operations except late-stage hepatectomy (HVH survival > LVH and MVH). The 5 year survival probability was similar between MVH and HVH for operations on late-stage cancers. Early and overall survival for gastrectomy, esophagectomy, and proctectomy were equivalent between MVH and HVH. While early and overall survival for pancreatectomy were benefited by HVH over MVH, the opposite was true for lobectomy/pneumonectomy, which were benefited by MVH over HVH; however, none of these differences were likely to have an effect clinically. Only hepatectomy patients demonstrated statistical and clinical significance in 5 year survival at HVH compared with MVH for overall survival. CONCLUSIONS: MVH hospitals performing sufficient complex common cancer operations demonstrate similar long-term survival for specific high-risk cancer operations to HVH. MVH provide an adjunctive model to the centralization of complex cancer surgery, while maintaining quality and access.

Thromboprophylaxis Timing After Blunt Solid Organ Injury: A Systematic Review and Meta-analysis.

INTRODUCTION: Trauma patients with blunt abdominal solid organ injuries are at high risk for venous thromboembolism (VTE), but the optimal time to safely administer chemical thromboprophylaxis is controversial, especially for patients who are managed nonoperatively due to increased risk of hemorrhage. We sought to compare failure of nonoperative management (NOM) and VTE events based on timing of chemical thromboprophylaxis initiation. METHODS: A systematic review was conducted in PubMed and Embase databases. Studies were included if they evaluated timing of initiation of chemical thromboprophylaxis in trauma patients who underwent NOM of blunt solid organ injuries. Outcomes included failure of NOM and incidence of VTE. A random-effects meta-analysis was performed comparing patients who received late (>48 h) versus early thromboprophylaxis initiation. RESULTS: Twelve retrospective cohort studies, comprising 21,909 patients, were included. Three studies, including 6375 patients, provided data on adjusted outcomes. Pooled adjusted analysis demonstrated no difference in failure of NOM in patients receiving late versus early thromboprophylaxis (odds ratio [OR] 0.92, 95% confidence interval [CI]:0.4-2.14). When including all unadjusted studies, even those at high risk of bias, there remained no difference in failure of NOM (OR 1.16, 95% CI:0.72-1.86). In the adjusted analysis for VTE events, which had 6259 patients between two studies, patients receiving late chemical thromboprophylaxis had a higher risk of VTE compared with those who received early thromboprophylaxis (OR 1.89, 95% CI:1.15-3.12). CONCLUSIONS: Based on current observational evidence, initiation of prophylaxis before 48 h is associated with lower VTE rates without higher risk of failure of NOM.

The Evaluation of Gallstone Disease in the Year Before Pancreatic Cancer Diagnosis.

INTRODUCTION: Patients with pancreatic cancer can present with a variety of insidious abdominal symptoms, complicating initial diagnosis. Early symptoms of pancreatic cancer often mirror those associated with gallstone disease, which has been demonstrated to be a risk factor for this malignancy. This study aims to compare the incidence of gallstone disease in the year before diagnosis of pancreatic ductal adenocarcinoma (PDAC) as compared to the general population, and evaluate the association of gallstone disease with stage at diagnosis and surgical intervention. METHODS: Patients with PDAC were identified from SEER-Medicare (2008-2015). The incidence of gallstone disease (defined as cholelithiasis, cholecystitis and/or cholecystectomy) in the 1 year before cancer diagnosis was compared to the annual incidence in an age-matched, sex-matched, and race-matched noncancer Medicare cohort. RESULTS: Among 14,654 patients with PDAC, 4.4% had gallstone disease in the year before cancer diagnosis. Among the noncancer controls (n = 14,654), 1.9% had gallstone disease. Both cohorts had similar age, sex and race distributions. PDAC patients with gallstone disease were diagnosed at an earlier stage (stage 0/I-II, 45.8% versus 38.1%, P < 0.0001) and a higher proportion underwent resection (22.7% versus 17.4%, P = 0.0004) compared to patients without gallstone disease. CONCLUSIONS: In the year before PDAC diagnosis, patients present with gallstone disease more often than the general population. Improving follow-up care and differential diagnosis strategies may help combat the high mortality rate in PDAC by providing an opportunity for earlier stage of diagnosis and earlier intervention.

Disparities in the Receipt of Recommended Curative Treatment for Patients with Early-Stage Hepatocellular Carcinoma.

BACKGROUND: In early-stage hepatocellular carcinoma (HCC), the receipt of recommended care is critical for long-term survival. Unfortunately, not all patients decide to undergo therapy. We sought to identify factors associated with the decision to decline recommended intervention among patients with early-stage HCC. METHODS: The National Cancer Database was queried for patients diagnosed with clinical stages I and II HCC (2004-2017). Cohorts were created based on the receipt or decline of recommended interventions-hepatectomy, liver transplantation, and ablation. Multivariable logistic regression identified predictors for declining intervention, and propensity score analysis was used to calculate the respective odds. Survival analysis was performed using the Kaplan-Meier method. RESULTS: Of 20,863 patients, 856 (4.1%) declined intervention. Patients who were documented as having declined intervention were more often Black (vs. other: OR, 1.3; 95% CI, 1.1-1.6; p = 0.0038), had Medicaid or no insurance (vs. Private, Medicare, or other government insurance): OR, 1.9; 95% CI, 1.6-2.3; p < 0.0001), lived in a low-income area (vs. other: OR, 1.4; 95% CI, 1.2-1.7; p < 0.0001), and received treatment at a non-academic center (vs. academic: OR, 2.1; 95% CI, 1.9-2.5; p < 0.0001). Patients who declined recommended interventions had worse survival compared to those who received treatment (22.9 vs. 59.2 months; p < 0.0001, respectively). CONCLUSIONS: Racial and socioeconomic disparities persist in the decision to undergo recommended treatment. Underutilization of treatment acts as a barrier to addressing racial and socioeconomic disparities in early-stage HCC outcomes.

The Effect of Hospital Versus Surgeon Volume on Short-Term Patient Outcomes After Pancreaticoduodenectomy: a SEER-Medicare Analysis.

BACKGROUND: The volume-outcome relationship has been well-established for pancreaticoduodenectomy (PD). It remains unclear if this is primarily driven by hospital volume or individual surgeon experience. OBJECTIVE: This study aimed to determine the relationship of hospital and surgeon volume on short-term outcomes of patients with pancreatic adenocarcinoma undergoing PD. METHODS: Patients >65 years of age who underwent PD for pancreatic adenocarcinoma were identified from the Surveillance, Epidemiology, and End Results (SEER)-Medicare database (2008-2015). Analyses were stratified by hospital volume and then surgeon volume, creating four volume cohorts: low-low (low hospital, low surgeon), low-high (low hospital, high surgeon), high-low (high hospital, low surgeon), high-high (high hospital, high surgeon). Propensity scores were created for the odds of undergoing surgery with high-volume surgeons. Following matching, multivariable analysis was used to assess the impact of surgeon volume on outcomes within each hospital volume cohort. RESULTS: In total, 2450 patients were identified: 54.3% were treated at high-volume hospitals (27.0% low-volume surgeons, 73.0% high-volume surgeons) and 45.7% were treated at low-volume hospitals (76.9% low-volume surgeons, 23.1% high-volume surgeons). On matched multivariable analysis, there were no significant differences in the risk of major complications, 90-day mortality, and 30-day readmission based on surgeon volume within the low and high hospital volume cohorts. CONCLUSION: Compared with surgeon volume, hospital volume is a more significant factor in predicting short-term outcomes after PD. This suggests that a focus on resources and care pathways, in combination with volume metrics, is more likely to achieve high-quality care for patients undergoing PD across all hospitals.

Impact of Patient Primary Language upon Immediate Breast Reconstruction After Mastectomy.

BACKGROUND: Preoperative decision-making in patients who speak a primary language other than English is understudied. We investigated whether patient primary language is associated with differences in immediate breast reconstruction (IBR) after mastectomy. PATIENTS AND METHODS: This retrospective observational study analyzed female patients undergoing mastectomy in the New Jersey State Inpatient Database (2009-2014). The primary outcome was the odds of IBR with a prespecified subanalysis of autologous tissue-based IBR. We used multivariable logistic regression and hierarchical generalized linear mixed models to control for patient characteristics and nesting within hospitals. RESULTS: Of 13,846 discharges, 12,924 (93.3%) specified English as the patient's primary language, while 922 (6.7%) specified a language other than English. Among English-speaking patients, 6178 (47.8%) underwent IBR, including 2310 (17.9%) autologous reconstructions. Among patients with a primary language other than English, 339 (36.8%) underwent IBR, including 93 (10.1%) autologous reconstructions. Unadjusted results showed reduced odds of IBR overall [odds ratio (OR) 0.64, 95% CI 0.55-0.73], and autologous reconstruction specifically (OR 0.52, 95% CI 0.41-0.64) among patients with a primary language other than English. After adjustment for patient factors, this difference persisted among the autologous subgroup (OR 0.64, 95% CI 0.51-0.80) but not for IBR overall. A hierarchical model incorporating both patient characteristics and hospital-level effects continued to show a difference among the autologous subgroup (OR 0.75, 95% CI 0.58-0.97). CONCLUSIONS: Primary language other than English was an independent risk factor for lower odds of autologous IBR after adjustments for patient and hospital effects. Focused efforts should be made to ensure that patients who speak a primary language other than English have access to high-quality shared decision-making for postmastectomy IBR.

Surveillance Patterns for Hepatocellular Carcinoma among Screening-Eligible Patients in the Medicare Population.

INTRODUCTION: Routine screening plays a critical role in the diagnosis of hepatocellular carcinoma (HCC), but not all patients undergo consistent surveillance. This study aims to evaluate surveillance patterns and their association with diagnosis stage and survival among Medicare patients at risk for HCC. PATIENTS AND METHODS: Patients with HCC and guideline-based screening eligibility who underwent imaging with ultrasound or abdominal magnetic resonance imaging (MRI) in the 2 years prior to diagnosis were identified from SEER-Medicare (2008-2015). Three surveillance cohorts were created: diagnostic (imaging only within 3 months prior), intermittent (imaging only once within 2 years prior, excluding diagnostic), and routine (at least two imaging encounters within 2 years prior, excluding diagnostic). Multivariable logistic regression was used to predict early-stage diagnosis (stage I-II), and 5-year survival was evaluated using the accelerated failure time method with Weibull distribution. RESULTS: Among 2261 eligible patients, 26.1% were classified as diagnostic, 15.8% as intermittent, and 58.1% as routine surveillance. The median age was 74 years (IQR 70-78 years). The majority of patients had a preexisting cirrhosis diagnosis (81.5%). Routine and intermittent, compared with diagnostic, surveillance were predictive of early-stage disease (routine: OR 2.05, 95% CI 1.64-2.56; intermittent: OR 1.43, 95% CI 1.07-1.90). Patients who underwent routine surveillance had significantly lower risk of mortality (HR 0.84, 95% CI 0.75-0.94) compared with the diagnostic group. CONCLUSIONS: A large proportion of screening-eligible patients do not undergo routine surveillance, which is associated with late-stage diagnosis and higher risk of mortality. These findings demonstrate the impact of timely and consistent healthcare access and can guide interventions for promoting surveillance among these patients.

Beyond insurance status: the impact of Medicaid expansion on the diagnosis of Hepatocellular Carcinoma.

BACKGROUND: Medicaid expansion has led to earlier stage diagnoses in several cancers but has not been studied in hepatocellular carcinoma (HCC), a disease with complex risk factors. We examined the effect of Medicaid expansion on the diagnosis of HCC and associations with county-level social vulnerability. METHODS: Patients with HCC <65 years of age were identified from the SEER database (2010-2016). County-level social vulnerability factors were obtained from the CDC SVI and BRFSS. A Difference-in-Difference analysis evaluated change in early-stage diagnoses (stage I-II) between expansion and non-expansion states. A Difference-in-Difference-in-Difference analysis evaluated expansion impact among counties with higher proportions of social vulnerability. RESULTS: Of 19,751 patients identified, 81.5% were in expansion states. Uninsured status decreased in expansion states (6.3%-2.4%, p < 0.0001) and remained unchanged in non-expansion states (12.7%-14.8%, p = 0.43). There was no significant difference in the incidence of early-stage diagnoses between expansion states and non-expansion states. Results were consistent when accounting for social vulnerability. CONCLUSION: Medicaid expansion was not associated with earlier stage diagnoses in patients with HCC, including those with higher social vulnerability. Unlike other cancers, expanded access did not translate into higher utilization of care in HCC, suggesting barriers on a multitude of levels.

The impact of upper gastrointestinal surgical volume on short term pancreaticoduodenectomy outcomes for pancreatic adenocarcinoma in the SEER-Medicare population.

BACKGROUND: Patients undergoing pancreaticoduodenectomy (PD) at low volume PD hospitals with high volume for other complex operations have comparable outcomes to high volume PD centers. We evaluated the impact of upper gastrointestinal operations (UGI) hospital volume on the outcomes of elderly, high risk patients undergoing PD. METHODS: Patients >65 years old who underwent PD for pancreatic adenocarcinoma were identified from SEER-Medicare (2008-2015). Four volume cohorts were created using PD tertiles and UGI median: low (1st tertile PD), mixed-low (2nd tertile PD, low UGI), mixed-high (2nd tertile PD, high UGI) and high (3rd tertile PD). Multivariable logistic and negative binomial regression assessed short-term complications. RESULTS: In total, 2717 patients were identified with a median age of 74.5 years. Patients treated at low, mixed-low and mixed-high volume hospitals, versus high volume, had higher risk of short-term complications, including major complications (low: OR 1.441, 95%CI 1.165-1.783; mixed-low: OR 1.374, 95%CI 1.085-1.740; mixed-high: OR 1.418, 95%CI 1.098-1.832) and 90-day mortality (low: OR 2.16, 95%CI 1.454-3.209; mixed-low: OR 2.068, 95%CI 1.347-3.175; mixed-high: OR 1.96, 95%CI 1.245-3.086). CONCLUSION: Patients with pancreatic adenocarcinoma who are older and more medically complex benefit from undergoing surgery at high volume PD centers, independent of the operative experience of that center.

Undertreatment of Gallbladder Cancer: A Nationwide Analysis.

BACKGROUND: Gallbladder cancer has a high mortality rate and an increasing incidence. The current National Comprehensive Cancer Network (NCCN) guidelines recommend resection for all T1b and higher-stage cancers. This study aimed to evaluate re-resection rates and the associated survival impact for patients with gallbladder cancer. METHODS: Patients with gallbladder adenocarcinoma who underwent resection were identified from the National Cancer Database (2004-2015). Re-resection was defined as definitive surgery within 180 days after the first operation. Propensity scores were created for the odds of a patient having a re-resection. Patients were matched 1:2. Survival analyses were performed using the Kaplan-Meier and Cox proportional hazard methods. RESULTS: The study identified 6175 patients, and 466 of these patients (7.6%) underwent re-resection. Re-resection was associated with younger median age (65 vs 72 years; p < 0.0001), private insurance (41.6% vs 27.1%; p < 0.0001), academic centers (50.4% vs 29.7%; p < 0.0001), and treatment location in the Northeast (22.8% vs 20.4%; p = 0.0011). Compared with no re-resection, re-resection was associated with pT stage (pT2: 47.6% vs 42.8%; p = 0.0139) and pN stage (pN1-2: 28.1% vs 20.7%; p < 0.0001), negative margins on final pathology (90.1% vs 72.6%; p < 0.0001), and receipt of chemotherapy (53.7% vs 35.8%; p < 0.0001). The patients who underwent re-resection demonstrated significantly longer overall survival (OS) than the patients who did not undergo re-resection (median OS, 44.0 vs 23.0 months; p < 0.0001). After propensity score-matching, re-resection remained associated with superior survival (median OS, 44.0 vs 31.0 months; p = 0.0004). CONCLUSIONS: Re-resection for gallbladder cancer is associated with improved survival but remains underused, particularly for early-stage disease.

Myofibroblasts Enhance Tumor Growth in a Novel Mouse Model of Colorectal Cancer.

BACKGROUND: Communication between colorectal cancer and stromal cells alters the tumor microenvironment to regulate locoregional disease and cancer progression. However, colon cancer-stromal cell interactions are difficult to study in vivo. Limitations of existing animal models include the use of immunocompromised mice, the inability to genetically modify a cell population in a single organ system, or a lack of anatomic context. Our goal was to develop a novel mouse model of colorectal cancer that is capable of studying tumor-stromal cell interactions in the native colon of immune-competent mice. METHODS: Primary mouse myofibroblasts were isolated from the colon of C57BL/6 mice and were grown in cell culture. Genetically defined (ApcΔ/Δ; Kras G12D/+; Trp53Δ/Δ) primary mouse colon cancer cells were suspended in serum-free media (20 µL) at varying concentrations (5 × 103 to 4 × 104 cells) either alone or in combination with syngeneic myofibroblasts (2 × 105 cells). After isoflurane anesthesia, a colonoscopy was performed on immune-competent 8- to 10-week-old C57BL/6 mice with endoscopic microinjection of the cell suspension into the submucosal space of the colon wall utilizing a small animal colonoscope. Surveillance endoscopy was used to assess for tumor growth, along with histologic analysis. Tumor size is presented on a grading system based on tumor diameter relative to colon circumference. RESULTS: A total of 33 mice were injected with a survival rate of 88% (29/33). Endoscopic microinjection of colorectal cancer cells resulted in dose-dependent tumor growth in the distal mouse colon that could be assessed endoscopically without animal sacrifice. Growth curves varied depending on the concentration of injected colorectal cancer cells, with no growth at the lowest concentration of injected cells (5 × 103 cells), progressive growth over 4 wk using 1-2 × 104 cells, while the highest colorectal cancer cell concentration (4 × 104 cells) led to larger tumors at week 1 followed by a steady decline in tumor growth over the 4-wk time period. Combined microinjection of 2 × 104 colorectal cancer cells with 2 × 105 myofibroblasts resulted in much larger tumors that persisted over the 4-wk time period and which were composed primarily of colorectal cancer cells. Immunofluorescence microscopy after coinjection of colorectal cancer cells with green fluorescent protein positive myofibroblasts confirmed that the injected myofibroblasts are present and remain viable over the 4-wk time period. CONCLUSIONS: Endoscopic submucosal microinjection of primary mouse colorectal cancer cells is feasible and leads to reliable and reproducible short-term growth of colon tumors in immune-competent mice. Coinjection of primary mouse colorectal cancer cells with syngeneic myofibroblasts leads to enhanced tumor growth. Coimplantation of colorectal cancer cells with syngeneic myofibroblasts provides a novel platform to study tumor-stromal interactions in the native colon of immune-competent mice.