Cholangiocarcinoma of the Middle Bile Duct: A Narrative Review.

Resectable cholangiocarcinoma (CCA) arising from the middle of the extrahepatic biliary tree has historically been classified as perihilar or distal CCA, depending on the operation contemplated or performed, namely the associated hepatectomy or pancreaticoduodenectomy, respectively. Segmental bile duct resection is a less invasive alternative for select patients harboring true middle extrahepatic CCA (MCC). A small, yet growing body of literature has emerged detailing institutional experiences with bile duct resection versus pancreaticoduodenectomy or concomitant hepatectomy for MCC. Herein, we provide a brief overview of the epidemiology, preoperative evaluation, and emerging systemic therapies for MCC, and narratively review the existing work comparing segmental resection with pancreaticoduodenectomy or less commonly, hepatectomy, for MCC, with emphasis on the surgical management and oncologic implications of the approach used.

The deimplementation of laboratory testing in low-risk patients as recommended by the American society of anesthesiologists: An ACS-NSQIP longitudinal analysis.

BACKGROUND: In 2012, the American Society of Anesthesiologists (ASA) published guidelines recommending against routine preoperative laboratory testing for low-risk patients to reduce unnecessary medical expenditures. The aim of this study was to assess the change in routine preoperative laboratory testing in low-risk versus higher-risk patients before and after release of these guidelines. METHODS: The ACS-NSQIP database, 2005-2018, was separated into low-risk versus higher-risk patients based upon a previously published stratification. The guideline implementation date was defined as January 2013. Changes in preoperative laboratory testing over time were compared between low- and higher-risk patients. A difference-in-differences model was applied. The primary outcome included any laboratory test obtained ≤90 days prior to surgery. RESULTS: Of 7,507,991 patients, 972,431 (13.0%) were defined as low-risk and 6,535,560 (87.0%) higher-risk. Use of any preoperative laboratory test declined in low-risk patients from 66.5% before to 59.6% after guidelines, a 6.9 percentage point reduction, versus 93.0%-91.9% in higher-risk patients, a 1.1 percentage point reduction (p < 0.0001, comparing percentage point reductions). After risk-adjustment, the adjusted odds ratio for having any preoperative laboratory test after versus before the guidelines was 0.77 (95% CI 0.76-0.78) in low-risk versus 0.93 (0.92-0.94) in higher-risk patients. In low-risk patients, lack of any preoperative testing was not associated with worse outcomes. CONCLUSIONS: While a majority of low-risk patients continue to receive preoperative laboratory testing not recommended by the ASA, there has been a decline after implementation of guidelines. Continued effort should be directed at the deimplementation of routine preoperative laboratory testing for low-risk patients.

Management of Colorectal Cancer Liver Metastases.

Ivey et al [...].

The United States experience with diagnosing and treating esophageal cancer during the SARS-CoV-2 pandemic: A retrospective cohort study.

The downstream effects on healthcare delivery during the initial wave of the COVID-19 pandemic remain unclear. The purpose of this study was to determine how the healthcare environment surrounding the pandemic affected the oncologic care of patients diagnosed with esophageal cancer. This was a retrospective cohort study evaluating patients in the National Cancer Database (2019-2020). Patients with esophageal cancer diagnoses were divided into pre-pandemic (2019) and pandemic (2020) groups. Patient demographics, cancer-related variables, and treatment modalities were compared. Among 26,231 esophageal cancer patients, 14,024 patients (53.5%) were in the pre-pandemic cohort and 12,207 (46.5%) were in the pandemic cohort. After controlling for demographics, patients diagnosed during the pandemic were more likely to have poorly differentiated tumors (odds ratio [OR] 1.24, 95% confidence interval [CI] 1.08-1.42), pathologic T3 disease compared to T1 (OR 1.25, 95% CI 1.02-1.53), positive lymph nodes on pathology (OR 1.36, 95% CI 1.14-1.64), and to be pathologic stage IV (OR 1.51, 95% CI 1.29-1.76). After controlling for oncologic characteristics, patients diagnosed during the pandemic were more likely to require at least two courses of systemic therapy (OR 1.78, 95% CI 1.48-2.14) and to be offered palliative care (OR 1.13, 95% CI 1.04-1.22). While these patients were offered curative therapy at lower rates, this became non-significant after risk-adjustment (p = .15). The pandemic healthcare environment was associated with significantly increased risk-adjusted rates of patients presenting with advanced esophageal cancer. While this led to significant differences in treatment, most of these differences became non-significant after controlling for oncologic factors.

Pulmonary metastasectomy is associated with survival after lung-only recurrence in pancreatic cancer.

BACKGROUND: After surgical resection of pancreatic ductal adenocarcinoma, 14% of patients have lung-only recurrence. We hypothesize that in patients with isolated lung metastases from pancreatic ductal adenocarcinoma, pulmonary metastasectomy offers a survival benefit with minimal additional morbidity after resection. METHODS: This was a single-institution, retrospective study of patients who underwent definitive resection of pancreatic ductal adenocarcinoma and later developed isolated lung metastases between 2009 and 2021. Patients were included if they carried a diagnosis of pancreatic ductal adenocarcinoma, underwent pancreatic resection with curative intent, and subsequently developed lung metastases. Patients were excluded if they developed multiple sites of recurrence. RESULTS: We identified 39 patients with pancreatic ductal adenocarcinoma and isolated lung metastases, 14 of whom underwent pulmonary metastasectomy. During the study period, 31 (79%) patients died. Across all patients, there was an overall survival of 45.9 months, a disease-free interval of 22.8 months, and survival after recurrence of 22.5 months. Survival after recurrence was significantly longer in patients who underwent pulmonary metastasectomy than those who did not (30.8 months vs 18.6 months, P < .01). There was no difference in overall survival between groups. However, patients who underwent pulmonary metastasectomy were significantly more likely to be alive 3 years after their diagnosis (100.0% vs 64%, P = .02) and 2 years after recurrence (79% vs 32%, P < .01) than those in who did not undergo pulmonary metastasectomy. No mortalities occurred related to pulmonary metastasectomy, and procedure-related morbidity was 7%. CONCLUSION: Patients who underwent pulmonary metastasectomy for isolated pulmonary pancreatic ductal adenocarcinoma metastases had significantly longer survival after recurrence and clinically meaningful survival benefit with minimal additional morbidity after pulmonary resection.

De-implementation of Axillary Dissection in Women Undergoing Mastectomy for Breast Cancer.

BACKGROUND: Completion axillary lymph node dissection (cALND) was standard treatment for breast cancer with positive sentinel lymph nodes (SLNs) until 2011, when data from the Z11 and AMAROS trials challenged its survival benefit in early stage breast cancer. We assessed the contribution of patient, tumor, and facility factors on cALND use in patients undergoing mastectomy and SLN biopsy. PATIENTS AND METHODS: Using the National Cancer Database, patients diagnosed from 2012 to 2017 who underwent upfront mastectomy and SLN biopsy with at least one positive SLN were included. A multivariable mixed effects logistic regression model was used to determine the effect of patient, tumor, and facility variables on cALND use. Reference effect measures (REM) were used to compare the contribution of general contextual effects (GCE) to variation in cALND use. RESULTS: From 2012 to 2017, the overall use of cALND decreased from 81.3% to 68.0%. Overall, younger patients, larger tumors, higher grade tumors, and tumors with lymphovascular invasion were more likely to undergo cALND. Facility variables, including higher surgical volume and facility location in the Midwest, were associated with increased use of cALND. However, REM results showed that the contribution of GCE to the variation in cALND use exceeded that of the measured patient, tumor, facility, and time variables. CONCLUSIONS: There was a decrease in cALND use during the study period. However, cALND was frequently performed in women after mastectomy found to have a positive SLN. There is high variability in cALND use, mainly driven by interfacility practice variation rather than specific high-risk patient and/or tumor characteristics.

Cannabis use and post-operative complications in patients undergoing pancreatic resection.

BACKGROUND: Many states have legalized medical cannabis with various reported therapeutic benefits. However, there is little data assessing the effects of cannabis on surgical outcomes. We sought to compare post-operative pancreatic resection complications between cannabis users and non-users. METHODS: This is a single-center, retrospective review of patients who underwent Whipple or distal pancreatectomy from 1/2017-12/2020. The primary outcome was any in-hospital complication, using Clavien-Dindo. Multivariable regression analysis was performed. RESULTS: There were 486 patients who underwent Whipple (n=346, 71.2%) or distal pancreatectomy (n=140, 28.8%). Overall, 21.4% (n=104) reported cannabis use, of whom 80.8% were current users. Cannabis users were younger (60 vs. 66 years, p < 0.001), and more likely to have smoked tobacco (p=0.04), but otherwise had similar demographics as non-users. There were 288 (59.3%) patients who developed an in-hospital complication (grade 1-2, 75.3%; grade 3-5, 24.7%). A trend towards increased complications was observed with tobacco smoking (OR 1.33, 95% CI 0.91-1.94, p=0.14), but no association of cannabis use with complications was observed (OR 0.93, 95% CI 0.58-1.47, p=0.74). DISCUSSION: A significant proportion of patients undergoing pancreatic resection report cannabis use. These results suggest that there was no association between cannabis use and post-operative complications, future prospective evaluation is warranted.

Unmeasured factors are associated with the use of completion lymph node dissection (CLND) in melanoma.

BACKGROUND: Completion lymph node dissection (CLND) was the standard treatment for patients with melanoma with positive sentinel lymph nodes (SLN) until 2017 when data from the DeCOG-SLT and MLST-2 randomized trials challenged the survival benefit of this procedure. We assessed the contribution of patient, tumor and facility factors on the use of CLND in patients with surgically resected Stage III melanoma. METHODS: Using the National Cancer Database, patients who underwent surgical excision and were found to have a positive SLN from 2012 to 2017 were included. A multivariable mixed-effects logistic regression model with a random intercept for the facility was used to determine the effect of patient, tumor, and facility variables on the risk of CLND. Reference effect measures (REMs) were used to compare the contribution of contextual effects (unknown facility variables) versus measured variables on the variation in CLND use. RESULTS: From 2012 to 2017, the overall use of CLND decreased from 59.9% to 26.5% (p < 0.0001). Overall, older patients and patients with government-based insurance were less likely to undergo CLND. Tumor factors associated with a decreased rate of CLND included primary tumor location on the lower limb, decreasing depth, and mitotic rate <1. However, the contribution of contextual effects to the variation in CLND use exceeded that of the measured facility, tumor, time, and patient variables. CONCLUSIONS: There was a decrease in CLND use during the study period. However, there is still high variability in CLND use, mainly driven by unmeasured contextual effects.

Comparing neoadjuvant chemotherapy with or without radiation therapy for pancreatic ductal adenocarcinoma: National Cancer Database cohort analysis.

BACKGROUND: Neoadjuvant treatment is important for improving the rate of R0 surgical resection and overall survival outcome in treating patients with pancreatic ductal adenocarcinoma (PDAC). However, the true efficacy of radiotherapy (RT) for neoadjuvant treatment of PDAC is uncertain. This retrospective study evaluated the treatment outcome of neoadjuvant RT in the treatment of PDAC. METHODS: Collected from the National Cancer Database, information on patients with PDAC who underwent neoadjuvant chemotherapy (NAC) and pancreatectomy between 2010 to 2016 was used in this study. Short- and long-term outcomes were compared between patients who received neoadjuvant chemoradiotherapy (NACRT) and NAC. RESULTS: The study included 6936 patients, of whom 3185 received NACRT and 3751 NAC. The groups showed no difference in overall survival (NACRT 16.1 months versus NAC 17.4 months; P = 0.054). NACRT is associated with more frequent margin negative resection (86.1 versus 80.0 per cent; P < 0.001) but a more unfavourable 90-day mortality than NAC (6.4 versus 3.6 per cent; P < 0.001). The odds of 90-day mortality were higher in the radiotherapy group (odds ratio 1.81; P < 0.001), even after adjusting for significant covariates. Patients who received NACRT received single-agent chemotherapy more often than those who received NAC (31.5 versus 10.7 per cent; P < 0.001). CONCLUSION: This study failed to show a survival benefit for NACRT over NAC alone, despite its association with negative margin resection. The significantly higher mortality in NACRT warrants further investigation into its efficacy in the treatment of pancreatic cancer.

De-implementation of Axillary Dissection in Women With Breast Cancer is Largely Driven By Site-level Contextual Effects.

OBJECTIVE: To assess the contribution of unknown institutional factors (contextual effects) in the de-implementation of cALND in women with breast cancer. SUMMARY OF BACKGROUND DATA: Women included in the National Cancer Database with invasive breast carcinoma from 2012 to 2016 that underwent upfront lumpectomy and were found to have a positive sentinel node. METHODS: A multivariable mixed effects logistic regression model with a random intercept for site was used to determine the effect of patient, tumor, and institutional variables on the risk of cALND. Reference effect measureswere used to describe and compare the contribution of contextual effects to the variation in cALND use to that of measured variables. RESULTS: By 2016, cALND was still performed in at least 50% of the patients in a quarter of the institutions. Black race, younger women and those with larger or hormone negative tumors were more likely to undergo cALND. However, the width of the 90% reference effect measures range for the contextual effects exceeded that of the measured site, tumor, time, and patient demographics, suggesting institutional contextual effects were the major drivers of cALND de-implementation. For instance, a woman at an institution with low-risk of performing cALND would have 74% reduced odds of havinga cALND than if she was treated at a median-risk institution, while a patient at a high-risk institution had 3.91 times the odds. CONCLUSION: Compared to known patient, tumor, and institutional factors, contextual effects had a higher contribution to the variation in cALND use.

Induction Chemotherapy Plus Neoadjuvant Chemoradiation for Esophageal and Gastroesophageal Junction Adenocarcinoma.

BACKGROUND: Neoadjuvant chemotherapy with concurrent radiotherapy (nCRT) is an accepted treatment regimen for patients with potentially curable esophageal and gastroesophageal junction (GEJ) adenocarcinoma. The purpose of this study is to evaluate whether induction chemotherapy (IC) before nCRT is associated with improved pathologic complete response (pCR) and overall survival (OS) when compared with patients who received nCRT alone for esophageal and GEJ adenocarcinoma. METHODS: Using the National Cancer Database (NCDB), patients who received nCRT and curative-intent esophagectomy for esophageal or GEJ adenocarcinoma from 2006 to 2015 were included. Chemotherapy and radiation therapy start dates were used to define cohorts who received IC before nCRT (IC + nCRT) versus those who only received concurrent nCRT before surgery. Propensity weighting was conducted to balance patient, disease, and facility covariates between groups. RESULTS: 12,460 patients met inclusion criteria, of whom 11,880 (95%) received nCRT and 580 (5%) received IC + nCRT. Following propensity weighting, OS was significantly improved among patients who received IC + nCRT versus nCRT (HR 0.82; 95% CI 0.74-0.92; p < 0.001) with median OS for the IC + nCRT cohort of 3.38 years versus 2.45 years for nCRT. For patients diagnosed from 2013 to 2015, IC + nCRT was also associated with higher odds of pCR compared with nCRT (OR 1.59; 95% CI 1.14-2.21; p = 0.007). CONCLUSION: IC + nCRT was associated with a significant OS benefit as well as higher pCR rate in the more modern patient cohort. These results merit consideration of a sufficiently powered prospective multiinstitutional trial to further evaluate these observed differences.

Outcomes After Converted Minimally Invasive to Open Esophagectomy in Patients With Esophageal Cancer.

BACKGROUND: The objective of this study was to evaluate the impact of unplanned conversion to open esophagectomy during minimally invasive esophagectomy (MIE) on postoperative morbidity and mortality for patients with esophageal cancer, as well as to evaluate the variables that influence the need for conversion. METHODS: This study was a retrospective analysis of patients with esophageal cancer who underwent open esophagectomy or MIE by either a laparothoracoscopic approach or a robotic approach from 2016 to 2018 by using the esophagectomy-specific American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database. Poisson regression models were used to analyze 30-day outcomes and risk factors for conversion to open esophagectomy during attempted MIE. RESULTS: A total of 2616 patients were identified. The overall conversion rate for MIE was 6.3%. Compared with completed MIE, patients requiring conversion to open esophagectomy had a significantly increased risk of 30-day mortality (risk ratio, 2.63; 95% confidence interval, 1.03 to 6.69) and experienced a variety of other postoperative complications. Patients requiring conversion to open esophagectomy during MIE also experienced worse perioperative outcomes when compared to patients who underwent planned open esophagectomy. Estimated surgical risk on the basis of the ACS NSQIP Surgical Risk Calculator was the only variable found to be independently associated with conversion from minimally invasive to open esophagectomy (risk ratio, 1.03; 95% confidence interval, 1.01 to 1.04, for each 10% increase in risk score). CONCLUSIONS: Unplanned conversion to open esophagectomy during MIE is associated with significantly greater morbidity and a 2.6-fold increased risk of death when compared with both completed MIE and planned open esophagectomy. The ACS NSQIP Surgical Risk Calculator may help identify patients preoperatively who are at higher risk for conversion to open esophagectomy during MIE.

Predictors of Disease Progression or Performance Status Decline in Patients Undergoing Neoadjuvant Therapy for Localized Pancreatic Head Adenocarcinoma.

INTRODUCTION: Neoadjuvant therapy (NT) is a growing strategy in localized head pancreatic adenocarcinoma (PDC). However, a significant portion of NT patients do not reach resection due to disease progression or performance status decline. We sought to identify predictors of disease progression or performance status decline during NT. METHODS: Retrospective cohort analysis of consecutive patients with localized head-PDC who received NT at a tertiary referral center between 2005 and 2017. Univariate and multivariate (MVA) analysis were performed to identify factors associated with disease progression or performance status decline during NT preventing surgical resection. RESULTS: A total of 479 patients with PDC underwent NT; 71.2% proceeded to surgery, 20.5% had disease progression, and 8.3% experienced performance status decline. Median OS was 28 [95% confidence interval (CI) 23.8-32.3], 12.8 (CI 11.2-14.3), and 6.9 (CI 5.2-9.4) months, respectively (p < 0.05). MVA predictors of disease progression were larger clinical CT tumor size [odds ratio (OR) 1.03, CI 1.0-1.1], unplanned change in NT regimen (OR 2.6, CI 1.0-6.9), hospital admission during NT (OR 2.2, CI 1.2-3.9), and lack of CA19-9 response (OR 4.4, CI 4.0-8.4). MVA predictors of performance status decline were increasing age (OR 1.1, CI 1.0-1.2), presence of pre-NT diabetes (OR 3.8, CI 1.3-11.3), hospital admission during NT (OR 14.0, CI 3.9-49.8), and lack of CA19-9 response (OR 4.7, CI 1.4-15.5). CONCLUSIONS: This analysis identifies several predictors of disease progression and performance status decline during NT for PDC. Knowledge of these factors informs the physician on the risks and limitations of NT and provides insight to guide patient selection and counseling.

Conversion to open surgery during minimally invasive esophagectomy portends worse short-term outcomes: an analysis of the National Cancer Database.

OBJECTIVE: The objectives were to determine factors associated with conversion to open surgery in patients with esophageal cancer who underwent minimally invasive esophagectomy (MIE, including laparo-thoracoscopic and robotic) and the impact of conversion to open surgery on patient outcomes. METHODS: We included patients from the National Cancer Database with esophageal and gastroesophageal junction cancer who underwent MIE from 2010 to 2015. Patient-, tumor-, and facility-related characteristics as well as short-term and oncologic outcomes were compared between patients who were converted to open surgery and those who underwent successful MIE without conversion to open surgery. Multivariable logistic regression models were used to analyze risk factors for conversion to open surgery from attempted MIE. RESULTS: 7306 patients underwent attempted MIE. Of these patients, 82 of 1487 (5.2%) robotic-assisted esophagectomies were converted to open, compared to 691 of 5737 (12.0%) laparo-thoracoscopic esophagectomies (p < 0.001). Conversion rates decreased significantly over the study period (ptrend = 0.010). Patient age, tumor size, and nodal involvement were independently associated with conversion. Facility minimally invasive cumulative volume and robotic approach were associated with decreased conversion rates. Patients whose MIEs were converted had increased 90-day mortality [Odds Ratio (OR) 1.49; 95% Confidence Interval (CI) 1.10, 2.02], prolonged hospital stay (OR 1.39; 95% CI 1.17, 1.66), and higher rates of unplanned readmission (OR 1.67; 95% CI 1.27, 2.20). No significant differences were found in surgical margins or number of lymph nodes harvested. CONCLUSION: Patients undergoing attempted MIE requiring conversion to open surgery had significantly worse short-term outcomes including postoperative mortality. Patient factors and hospital experience contribute to conversion rates. These findings should inform surgeons and patients considering esophagectomy for cancer.

A nomogram to predict node positivity in patients with thin melanomas helps inform shared patient decision making.

OBJECTIVE: To develop a nomogram to estimate the probability of positive sentinel lymph node (+SLN) for patients with thin melanoma and to characterize its potential impact on sentinel lymph node biopsy (SLNB) rates. METHODS: Patients diagnosed with thin (0.5-1.0 mm) melanoma were identified from the National Cancer Database 2012 to 2015. A multivariable logistic regression model was used to examine factors associated with +SLN, and a nomogram to predict +SLN was constructed. Nomogram performance was evaluated and diagnostic test statistics were calculated. RESULTS: Of the 21 971 patients included 10 108 (46.0%) underwent SLNB, with a 4.0% +SLN rate. On multivariable analysis, age, Breslow thickness, lymphovascular invasion, ulceration, and Clark level were significantly associated with SLN status. The area under the receiver operating curve was 0.67 (95% confidence interval, 0.65-0.70). While 15 249 (69.4%) patients had either T1b tumors or T1a tumors with at least one adverse feature, only 2846 (13.0%) had a nomogram predicted probability of a +SLN ≥5%. Using this cut-off, the indication for a SLNB in these patients would be reduced by 81.3% as compared to the American Joint Committee on Cancer 8th edition staging criteria. CONCLUSIONS: The risk predictions obtained from the nomogram allow for more accurate selection of patients who could benefit from SLNB.

Recurrent Solid Pseudopapillary Neoplasm of Pancreas: Case Report and Review of Literature.

Background: Solid pseudopapillary neoplasm of pancreas is a rare tumor with a low potential for metastasis and recurrence. Long-term outcomes after surgical resection are excellent and recurrences after an R0 resection are extremely rare. Case Presentation: We present an unusual case of a 42-year-old man who had a recurrence of his solid pseudopapillary tumor 4 years after undergoing a distal pancreatectomy and splenectomy and then again a year after his reresection. Conclusions: The lack of histological features deemed to be suggestive of a malignant variant and the aggressive clinical course seen in this case is remarkable. It underscores the fact that despite the low incidence, recurrences of solid pseudopapillary neoplasms of the pancreas do occur and it can be very difficult to predict malignant potential based on radiological or histopathological features.

Time-related changes in the prognostic significance of the total number of examined lymph nodes in node-negative pancreatic head cancer.

BACKGROUND AND OBJECTIVES: The aim of study was to assess time trends in the association between the total number of lymph nodes examined (TNLE) and survival in patients operated for adenocarcinoma of the head of pancreas. METHODS: Patients operated for node-negative adenocarcinoma of the head of pancreas between 1988 and 2007 were identified from the Surveillance, Epidemiology and End Results (SEER) database. Patients diagnosed between 1988 and 2002 were compared to those diagnosed between 2003 and 2007. RESULTS: A total of 3,406 patients were included. Although TNLE was associated with survival, the effect was not uniform. Compared to patients with >12 TNLE, survival decreased with lower TNLE (4-12 TNLE: hazard ratio [HR] 1.27, 95% CI 1.10-1.46; <4 TNLE: HR 1.39, 95% CI 1.20-1.60) among patients diagnosed between 1988 and 2002. In contrast, for those diagnosed between 2003 and 2007, while there was decreased survival for those with <4 nodes (HR 1.44, 95% CI 1.22-1.71), no effect was seen for patients with TNLE 4-12 (HR 0.98, 95% CI 0.85-1.14). CONCLUSION: The prognostic significance of the TNLE in patients operated for adenocarcinoma of the head of the pancreas is not constant over time.

Nodal status, number of lymph nodes examined, and lymph node ratio: what defines prognosis after resection of colon adenocarcinoma?

BACKGROUND: Lymph node ratio (LNR) has been proposed as an optimal staging variable for colorectal cancer. However, the interactive effect of total number of lymph nodes examined (TNLE) and the number of metastatic lymph nodes (NMLN) on survival has not been well characterized. STUDY DESIGN: Patients operated on for colon cancer between 1998 and 2007 were identified from the Surveillance, Epidemiology, and End Results database (n = 154,208) and randomly divided into development (75%) and validation (25%) datasets. The association of the TNLE and NMLN on survival was assessed using the Cox proportional hazards model with terms for interaction and nonlinearity with restricted cubic spline functions. Findings were confirmed in the validation dataset. RESULTS: Both TNLE and NMLN were nonlinearly associated with survival. Patients with no lymph node metastasis had a decrease in the risk of death for each lymph node examined up to approximately 25 lymph nodes, while the effect of TNLE was negligible after approximately 10 negative lymph nodes (NNLN) in those with lymph node metastasis. The hazard ratio varied considerably according to the TNLE for a given LNR when LNR ≥ 0.5, ranging from 2.88 to 7.16 in those with an LNR = 1. The independent effects of NMLN and NNLN on survival were summarized in a model-based score, the N score. When patients in the validation set were categorized according to the N stage, the LNR, and the N score, only the N score was unaffected by differences in the TNLE. CONCLUSIONS: The effect of the TNLE on survival does not have a unique, strong threshold (ie, 12 lymph nodes). The combined effect of NMLN and TNLE is complex and is not appropriately represented by the LNR. The N score may be an alternative to the N stage for prognostication of patients with colon cancer because it accounts for differences in nodal samples.