Melanoma Deaths by Thickness: Most Melanoma Deaths Are Not Attributable to Thin Melanomas.

INTRODUCTION: Previous population-based studies have reported that the majority of melanoma mortality is related to patients with thin (≤1 mm Breslow thickness) melanomas. The aim of the present study was to evaluate the relative proportion of melanoma-specific deaths across all stages of melanoma at diagnosis over the past 20 y in the United States. METHODS: A review of all cutaneous melanoma cases in the US Surveillance, Epidemiology, and End Results registry from 2004 to 2020 was performed. Breslow thickness was categorized as thin (≤1.0 mm), intermediate (>1-4 mm), or thick (>4 mm). All-cause deaths and melanoma-specific deaths were compared across tumor thickness and stage groups at diagnosis. Survival analysis was performed with nonmelanoma deaths considered as a competing risk to estimate the cumulative incidence of melanoma-specific death. RESULTS: Most melanoma deaths occurred in patients who initially presented with local disease (53%) compared to regional (36%) or distant (11%) disease (P < 0.001). However, most (66%) of the melanoma-specific deaths in patients who presented with localized disease were in those with intermediate or thick (i.e., Breslow thickness >1.0 mm) primary tumors compared to those with thin melanomas (34%). The cumulative incidence of melanoma-specific death at 10 y in patients with localized thin melanomas at the time of diagnosis was 2.6% (95% confidence intervals 2.5%-2.7%). CONCLUSIONS: The public health burden in terms of melanoma-specific mortality is related to patients with tumors >1 mm Breslow thickness, many of whom have regional and distant metastatic disease at the time of diagnosis, not patients with thin melanomas.

Interval Sentinel Lymph Nodes With the Use of Routine Lymphoscintigraphy in Extremity Melanoma.

INTRODUCTION: Lymphoscintigraphy (LS) helps identify drainage to interval (epitrochlear or popliteal) lymph node basins for extremity melanomas. This study evaluated how often routine LS evaluation identified an interval sentinel lymph node (SLN) and how often that node was found to have metastasis. METHODS: A single institution, retrospective study identified patients with an extremity melanoma who underwent routine LS and SLN biopsy over a 25-y period. Comparisons of factors associated with the identification of interval node drainage and tumor status were made. RESULTS: In 634 patients reviewed, 5.7% of patients drained to an interval SLN. Of those biopsied, 29.2% were positive for micrometastases. Among patients with biopsies of both the traditional and interval nodal basins, nearly 20% had positive interval nodes with negative SLNs in the traditional basin. Sex, age, thickness, ulceration, and the presence of mitotic figures were not predictive of identifying an interval node on LS, nor for having disease in an interval node. Anatomic location of the primary melanoma was the only identifiable risk factor, as no interval nodes were identified in melanomas of the thigh or upper arm (P ≤ 0.001). CONCLUSIONS: Distal extremity melanomas have a moderate risk of mapping to an interval SLN. Routine LS should be considered in these patients, especially as these may be the only tumor-positive nodes. However, primary extremity melanomas proximal to the epitrochlear or popliteal nodal basins do not map to interval nodes, and improved savings and workflow could be realized by selectively omitting routine LS in such patients.

Barriers to resection following neoadjuvant chemotherapy for resectable pancreatic adenocarcinoma: A national and local perspective.

BACKGROUND: Neoadjuvant chemotherapy (NAC) use for pancreatic ductal adenocarcinoma (PDAC) has increased, but some patients never get resection following NAC. METHODS: Data from January 2012 to December 2019 for all clinically resectable patients across two health networks were utilized, as well as data from the ACS NCDB registry. Univariate testing, multivariable logistic regression, and survival analyses were employed to evaluate failure to resection after neo-adjuvant chemotherapy. RESULTS: Of the 10 007 registry patients eligible for resection, the resected group was younger (64.6 vs. 69.5 years; p < 0.001) and had a slightly lower mean comorbidity index (0.41 vs. 0.45; p < 0.001) than the nonsurgical group. The nonsurgical group was composed of a higher percentage of Black and Hispanic patients (17.5 vs. 13.1%; p < 0.001). After adjusting for age and comorbidities, the factors associated with decreased probability of resection after NAC were evaluation at a community hospital (OR 2.4), Black or Hispanic race (OR 1.6), areas of increased high school drop-out rates (OR 1.4), and lack of private health insurance (OR 1.3). The median overall survival for nonsurgery was markedly worse than the surgical cohort (10.6 vs. 26.6 months; p < 0.001). The most frequent reasons for a lack of definitive resection were operative upstaging to unresectable (39.6%), patient preference (14.5%), progression on NAC (13.2%), deconditioning or comorbidity severity (12.5%), and nonreferral to a surgeon (8.8%). CONCLUSIONS: Racial, economic, and educational disparities have a considerable influence on the successful completion of a neoadjuvant approach for resectable PDAC. A comprehensive closed or highly collaborative/communicative multidisciplinary neoadjuvant program is optimal for treatment success and completion.

Combined pre-operative risk score predicts pancreatic leak after pancreatic resection.

BACKGROUND: Post-operative pancreatic fistula (POPF) is a major complication following pancreatectomy and is currently difficult to predict pre-operatively. This study aims to validate pre-operative risk factors and develop a novel combined score for the prediction of POPF in the pre-operative setting. METHODS: Data were collected from 2016 to 2021 for radiologic main pancreatic duct diameter (MPD), body mass index (BMI), physical status classified by American Society of Anesthesiologists (ASA), polypharmacy, mean platelet ratio (MPR), comorbidity-polypharmacy score (CPS), and a novel Combined Pancreatic Leak Prediction Score (CPLPS) (derived from MPD diameter, BMI, and CPS) were obtained from pre-operative data and analyzed for their independent association with POPF occurrence. RESULTS: In total, 166 patients who underwent pancreatectomy with pancreatic leak (Grade A, B, and C) occurring in 51(30.7%) of patients. Pre-operative radiologic MPD diameter < 4 mm (p < 0.001), < 5 mm (p < 0.001), < 6 mm (p = 0.001), BMI ≥ 25 (p = 0.009), and ≥ 30 (p = 0.017) were independently associated with the occurrence of pancreatic leak. CPLPS was also predictive of pancreatic leak following pancreatectomy on univariate (p = 0.005) and multivariate analysis (p = 0.036). CONCLUSION: MPD and BMI were independent risk factors predictive for the development of pancreatic leak. CPLPS, was an independent predictor of pancreatic leak following pancreatectomy and could be used to help guide surgical decision making and patient counseling.

Does Stage Migration Occur as a Consequence of Omitting Completion Lymph Node Dissection for Melanoma?

INTRODUCTION: Completion lymph node dissection (CLND) is no longer recommended routinely in the treatment of melanoma. CLND omission may understage patients for whom the distinction between stage IIIA and IIIB-C could alter adjuvant therapy recommendations. The aim of this study is to determine if stage migration has occurred with the declining use of CLND. METHODS: Patients with clinically node-negative ≥ T1b cutaneous melanoma were identified from the National Cancer Database (NCDB) from 2012 to 2018. CLND utilization and changes in AJCC staging were analyzed. Patients undergoing sentinel lymph node biopsy (SLNB) alone were compared with those undergoing SLNB + CLND. RESULTS: Overall, 68,933 patients met inclusion criteria and 60,536 underwent SLNB, of which 9031 (14.9%) were tumor positive. CLND was performed in 3776 (41.8%). Patients undergoing CLND were younger (58 versus 62 years, p < 0.0001) and more likely male (61.5% versus 57.9%, p = 0.0005). Patients were more likely to have an N classification >N1a if they received SLNB + CLND (36.8%) versus SLNB alone (19.3%), p < 0.0001. This translated to a small difference in stage IIIA patients between groups (SLNB alone 34.0%, SLNB + CLND 31.8%, p < 0.0001). Of the patients with T1b/T2a tumors who would be upstaged from IIIA to IIIC with identification of additional positive nodes, IIIC incidence was only slightly higher after SLNB + CLND compared with SLNB alone (4.4% versus 1.1%, p < 0.0001). CLND utilization dramatically decreased from 59% in 2012 to 12.6% in 2018, p < 0.0001. However, the incidence of stage IIIA disease for all patients remained stable over the 7-year study period. CONCLUSIONS: While the utilization of CLND after positive SLNB has declined dramatically in the last 7 years, stage migration that may affect adjuvant therapy decisions has not occurred to a clinically meaningful degree.

Preventing Futile Liver Resection: A Risk-Based Approach to Surgical Selection in Major Hepatectomy for Colorectal Cancer.

BACKGROUND: Early recurrence following liver resection for metastatic colorectal cancer generally portends poor survival. We sought to identify factors associated with early disease recurrence after major hepatectomy for metastatic colorectal cancer in order to improve patient selection and prevent futile hepatectomy. METHODS: Sequential major (four or more segments) liver resections performed for metastatic colorectal cancer between 1995 and 2019 were selected from our prospectively maintained database. Univariate analyses, multivariable regression modelling, and survival analyses were used to identify predictors of futile resection (recurrence within 6 months of hepatectomy). RESULTS: Of 259 patients included, the median age was 61.3 years (interquartile range [IQR] 15.3) and the median number of liver tumors was 3.0 (IQR 2.0); 78.0% of patients received prehepatectomy chemotherapy. Surgeries were right (56.4%), left (19.3%), and extended hepatectomy (24.3%). Futile resection occurred in 26 (12.6%) patients. Margin positivity was similar in the futile resection group compared with the non-futile resection group (11.5% vs. 11.4%). Extrahepatic disease that disappeared with chemotherapy was present in 23.1% of patients with a futile resection and 7.2% of those without (p = 0.019). After multivariable regression, the factors predictive of futile resection were extrahepatic disease (odds ratio [OR] 5.6; p = 0.004), more than three liver lesions (OR 4.9; p = 0.001), and extended hepatectomy (OR 2.6; p = 0.038). Notably, 70.8% of futile recurrences occurred within the liver remnant and 20.8% were pulmonary metastases. Overall survival was 11.7 months (95% confidence interval [CI] 7.1-16.2) for the futile resection cohort versus 45.6 (95% CI 39.1-52.1) for non-futile hepatectomies (p < 0.001). CONCLUSIONS: Futile hepatic resection can be predicted based on preoperative factors and carries a poor prognosis. Improved risk stratification for futility will aid in patient selection and treatment discussions.

Locally advanced pancreatic cancer: a reliable contraindication to resection in the modern era?

BACKGROUND: The aim of this study is to present radiologically designated LAPC found to be resectable upon surgical exploration and evaluate the outcomes of such resections. METHODS: Sequential LAPC patients between 2013 and 2019 were staged and underwent resection were included in the analysis of both perioperative and long-term outcomes. RESULTS: Twenty-eight patients with radiologically-designated LAPC underwent surgical resection after chemotherapy with a median follow-up of 31.7 m,75% underwent pancreaticoduodenectomy. The margin positivity and local recurrence rates were 21.4% and 35.7%, respectively. When compared to the 30 BRPC controls, the LAPC group had a higher rates of an arterial resection (11vs.1; p = 0.002), but the groups were similar with regard to all other preoperative and intraoperative variables (p < 0.05). Perioperative morbidity rates were similar (25.9%vs21.4%; p = 0.53). The LAPC and BRPC groups were also equivalent with respect to median recurrence-free survival (9.0mo; 95%CI 6.3, 11.7vs.8.3mo; 95%CI 5.4, 11.2) and median overall survival (19.9mo; 95%CI 17.0, 22.7 vs. 19.9mo; 95%CI 14.8, 25.1), respectively. CONCLUSION: Despite a radiologic designation of locally advanced pancreatic cancer, certain subtypes of LAPC warrant surgical exploration provided the operative surgeon is prepared for major arterial and/or venous resection. Pancreatectomy in these patients has acceptable morbidity and oncologic outcomes, similar to patients who are radiologically borderline resectable.

An Improved Staging System for Locally Advanced Pancreatic Cancer: A Critical Need in the Multidisciplinary Era.

BACKGROUND: Locally-advanced pancreatic cancer (LAPC) is traditionally considered stage III unresectable disease. Advances in induction systemic therapy regimens, surgical technique, and perioperative care have led to successful resection of an increasing number of these tumors with reasonable perioperative outcomes and disease-free intervals. Certain anatomic characteristics that meet criteria for locally-advanced disease, however, are more likely to result in a successful surgical outcome. METHODS: A practical and consistent system is needed to communicate such nuance between surgical and nonsurgical oncologists for optimal treatment planning and to improve recording for cancer registries and research studies. RESULTS: The present study proposes a novel subclassification system for stage III pancreatic cancers based on their pattern of vascular involvement and examines the current evidence for resection in each scenario. Introducing needed detail into the current catch-all stage III categorization will help to direct patient referrals and increase the body of knowledge about the variable presentations of this complex malignancy. CONCLUSION: This proposed staging revision for LAPC is designed to convey more actionable tumor descriptions for treating oncologists, clinical trial eligibility, and surgical patient selection in the era of effective induction systemic therapy.

Predictors of Nonsentinel Lymph Node Metastasis in Cutaneous Melanoma: A Systematic Review and Meta-Analysis.

BACKGROUND: Although completion lymph node dissection (CLND) is not routinely performed for a positive sentinel lymph node (SLN) anymore, adjuvant therapy depends on the risk factors available from SLN biopsy, including the risk of nonsentinel node metastases (NSNM). A systematic review and meta-analysis was performed in an attempt to identify risk factors that could be used to predict the risk of NSNM. MATERIALS AND METHODS: Medline, Web of Science, Embase, and Cochrane were searched for articles discussing predictive factors for NSNM. PRISMA guidelines were followed, and RevMan software was used to calculate pooled odds ratios (OR) using the Mantel-Haenszel test. RESULTS: Fifty publications were suitable for additional analysis. The clinical and primary tumor factors that were consistently identified as risk factors for NSNMs were: age >50, T stage 3 or 4, Clark level IV/V, ulceration, microsatellitosis, lymphovascular invasion, nodular histology, and extremity versus trunk primary tumor location. SLN factors that predicted NSNMs were >1 positive SLN, SLN micrometastatic tumor burden, diameter >2 mm, extracapsular extension, nonsubcapsular location (Dewar), and Rotterdam > 1 mm or ≥ 0.1 mm. CONCLUSIONS: The findings in this study support that many clinical and pathologic risk factors that can be assessed with SLN biopsy alone can be used to predict the risk of NSNMs. The factors identified in this review should be evaluated in clinical prediction models to predict the risk of NSNMS, a prediction that may be used to select patients for adjuvant therapy in high-risk melanoma.

A literature-based treatment algorithm for low-grade neuroendocrine liver metastases.

BACKGROUND: The optimal timing of treatment of liver metastases from low-grade neuroendocrine tumors (LG-NELM) varies significantly due to numerous treatment modalities and the literature supporting various treatment(s). This study sought to create and validate a literature-based treatment algorithm for LG-NELM. METHODS: A treatment algorithm to maximize overall survival (OS) was designed using peer-reviewed articles evaluating treatment of LG-NELM. This algorithm was retrospectively applied to patients treated for LG-NELM at our institution. Deviation was determined based on whether or not a patient received treatment consistent with that recommended by the algorithm. Patients who did and did not deviate from the algorithm were compared with respect to OS and number of treatments. RESULTS: Applying our algorithm to a 149-patient cohort, 57 (38%) deviated from recommended treatment. Deviation occurred in the form of alternative (28, 49%) versus additional procedures (29, 51%). Algorithm deviators underwent significantly more procedures than non-deviators (median 1 vs. 2, p < 0.001). Cox model indicated no difference in OS associated with algorithm deviation (HR 1.19, p = 0.58) when controlling for age and tumor characteristics. CONCLUSION: This literature-based algorithm helps standardize treatment protocols in patients with LG-NELM and can reduce cost and risk by minimizing unnecessary procedures. Prospective implementation and validation is required.

The Sunbelt Melanoma Trial.

The Sunbelt Melanoma Trial, a multicenter, prospective randomized clinical study, evaluated the role of high-dose interferon alfa-2b (HDI) therapy for patients with a single positive sentinel lymph node (SLN) metastasis treated with a completion lymph node dissection (CLND). A second protocol in the trial evaluated the prognostic significance of using molecular markers to identify submicroscopic metastases in sentinel lymph nodes that were negative by routine pathologic analysis. The role of CLND with or without adjuvant HDI was evaluated in this group of patients. The results of the study demonstrated that adjuvant HDI offered no survival benefit for patients with a single positive SLN in terms of disease-free or overall survival. Molecular staging using polymerase chain reaction (PCR) for melanoma markers did not identify a high-risk group of patients at increased risk of melanoma recurrence. Additional treatment of these patients who were PCR-positive with either CLND alone or CLND plus HDI did not improve their survival. Additional studies from the Sunbelt Melanoma Trial helped to validate the operational standards of the SLN biopsy procedure and defined the complication rates for both SLN biopsy and CLND. A prognostic risk calculator has been developed from trial data, and the importance of different micrometastatic tumor burden measurements was reported. Although the Sunbelt Melanoma Trial did not demonstrate an improvement in survival with HDI, it is an important trial that highlights the significance of surgeon-initiated randomized clinical trials that incorporate surgical techniques, molecular biomarkers, and adjuvant therapy.

Impact of Perfusate Glucose Concentration on Perioperative Outcomes in Patients Undergoing Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy.

BACKGROUND: Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) is a common treatment for peritoneal surface malignancies but no standard carrier solution currently exists for the procedure. This study compared a standard low-dextrose perfusate to a higher-dextrose dialysate that has previously shown favorable impact on perioperative patient outcomes in trauma settings. MATERIALS AND METHODS: A single-center retrospective study identified patients undergoing CRS/HIPEC from 2008 to 2019 with recorded dextrose concentration of administered perfusate. An institutional shift to a higher-dextrose solution was made in late 2015. Comparisons of preoperative factors, intraoperative and postoperative glucose levels, and postoperative outcomes were made using the chi-square test, Fisher's exact test, Wilcoxon rank sum test, or repeated measures analysis of variance. RESULTS: There were 97 patients in the study, 73 (75%) in the low-dextrose group and 24 (25%) in the high-dextrose group. There was no significant difference in peak intraoperative blood glucose levels between the 1.5% (mean 230 mg/dL) and the 2.5% group (mean 199 mg/dL, P = 0.15). Daily postoperative glucose values were also not statistically different (repeated measures analysis of variance, P = 0.18). Median length of stay was slightly lower for the high-dextrose group (10 d, interquartile range 8-15) than that for the low-dextrose group (12 d, interquartile range 9-17), but was not statistically significant (P = 0.29). Return of bowel function and resumption of diet were similar between the groups. The high-dextrose group had a lower rate of overall complications (20.8%) than the low-dextrose group (49.3%, P = 0.0143). Ninety-day mortality was equivalent between the two groups (2.7% low-dextrose, 4.2% high-dextrose, P = 1.0). CONCLUSIONS: Use of 2.5% dextrose-containing perfusate appears safe for CRS/HIPEC operations, does not negatively impact intraoperative or postoperative glucose levels, and may be associated with a decreased risk of complications.

Identifying factors impacting the efficacy of postmastectomy radiotherapy in patients with early-stage breast cancer and one to two positive lymph nodes.

INTRODUCTION: In women with T1-2 breast cancer and one to two positive axillary lymph nodes (LN) at low risk for recurrence, postmastectomy radiation therapy (PMRT) may provide insufficient benefit to justify its toxicity. This study evaluated the interaction of factors associated with overall survival (OS) after PMRT in these patients. METHODS: The National Cancer Database was queried for women with T1-2 breast cancer undergoing mastectomy with one to two positive LN identified on lymphadenectomy. Patients were grouped according to number of positive LN and then stratified by PMRT use. Differences in OS were evaluated. RESULTS: Multivariable modeling demonstrated an interaction effect of age on the efficacy of PMRT. In patients more than or equal to 60 years old, PMRT was associated with improved survival when adjusting for age and tumor grade in patients with 1 to 2 positive LN (risk ratio = 0.62, 95% confidence interval = 0.40-0.93, P = .018). In patients less than 60 years old, tumor size and grade, but not PMRT, were associated with improved OS. CONCLUSION: For women with T1-2 breast cancer and one to two positive LN, PMRT's association with OS is influenced by age, tumor grade, and number of positive LN. PMRT appears to be associated with improvements in OS in older patients, but not younger patients, regardless of tumor size or nodal status.

Optimal perfusion chemotherapy: A prospective comparison of mitomycin C and oxaliplatin for hyperthermic intraperitoneal chemotherapy in metastatic colon cancer.

BACKGROUND: Peritoneal carcinomatosis of colorectal adenocarcinoma (CRC) origin is common and is the second-most frequent cause of death in colorectal cancer. There is survival benefit to surgical resection plus hyperthermic intraperitoneal chemotherapy (HIPEC) for patients with metastatic CRC. However, there remains controversy between oxaliplatin (Oxali) and mitomycin C (MMC), as the agent of choice. METHODS: A review of our 285 patients prospective HIPEC database from July 2007 to May 2018 identified 48 patients who underwent cytoreductive surgery plus HIPEC with MMC or Oxali. Patients were stratified based on preoperative and postoperative peritoneal cancer indices (PCI). The primary outcomes of survival and progression-free survival were compared. RESULTS: Type of HIPEC chemotherapy was not found to be predictive of overall survival. Preoperative PCI (P = .04), preoperative response to chemotherapy (P = .0001), and postoperative PCI (P = .05) were predictive for overall survival. CONCLUSIONS: MMC or Oxali based HIPEC chemotherapy are both safe and effective for the management of peritoneal only metastatic CRC. Both perfusion therapies should be considered with all patients receiving modern induction chemotherapy.

Correlating serum alpha-fetoprotein in hepatocellular carcinoma with response to Yttrium-90 transarterial radioembolization with glass microspheres (TheraSphere™).

BACKGROUND: Few studies have assessed the relationship between serum alpha-fetoprotein (AFP) and yttrium-90 (Y-90) radioembolization response in hepatocellular carcinoma (HCC). The objective of the study was to evaluate whether peri-procedural serum AFP was correlated with Y-90 therapy response in HCC. METHODS: Patients undergoing Y-90 radioembolization with glass microspheres (TheraSphere™) for HCC between 2006 and 2013 at a single center were evaluated. The relationship between AFP and 6-month radiographic improvement (complete or partial response by modified RECIST criteria), overall (OS), and disease-specific survival (DSS) were analyzed. RESULTS: Seventy-four patients underwent a total of 124 Y-90 infusions. Median age was 65 years, median AFP was 37 ng/mL (range: 2-112,593 ng/mL) and median model for end-stage liver disease score was 6.2 (range:1.8-11.2). Increased AFP was not associated with radiographic improvement (odds ratio (OR) = 0.99, 95% confidence interval (CI) = 0.75-1.30, p = 0.92). Median OS was 15.2 months and was increased in patients with low AFP compared to high AFP (30.8 months vs. 7.8 months, p < 0.001). On multivariable regression analysis, increased AFP was associated with worse OS (OR = 1.11, 95%CI = 1.01-1.22, p = 0.034) and DSS (OR = 1.13, 95%CI = 1.03-1.25, p = 0.018). CONCLUSION: Pre-infusion AFP independently predicted survival after Y-90 treatment for HCC, but not radiographic response, and can help guide treatment decisions.

Age and Lymphovascular Invasion Accurately Predict Sentinel Lymph Node Metastasis in T2 Melanoma Patients.

BACKGROUND: The risk of sentinel lymph node (SLN) metastasis in melanoma is related directly to tumor thickness and inversely to age. The authors hypothesized that for T2 (thickness 1.1-2.0 mm) melanoma, age, and other factors may be able to identify a cohort of patients with a low risk of SLN metastases. METHODS: The authors developed logistic regression models to predict positive SLNs in patients undergoing SLN biopsy for T2 melanoma using the National Cancer Database. Classification and regression-tree analysis were used to identify groups of patients with high and low risk for SLN metastases. The prediction model then was applied to a separate data set from a multicenter randomized clinical trial. RESULTS: The study identified 12,918 patients with T2 melanoma undergoing SLN biopsy with clinically node-negative melanoma. In the multivariable analysis, increasing thickness, younger age, lymphovascular invasion (LVI), mitotic rate of 1/mm2 or more, axial location, and Clark level of 4 or 5 were independent risk factors for SLN metastases. A cohort based on age (> 56 years) and no LVI was identified with a relatively low risk (7.8%; 95% confidence interval 7.2-8.4%) of SLN metastases. The independent data set of 1531 patients with T2 melanoma confirmed these findings. Among elderly patients (age > 75 years) with melanoma 1.2 mm or smaller and no LVI, the risk of a positive SLN was 4.9% (95% confidence interval 3.3-7.1%). CONCLUSIONS: Younger age and LVI are powerful predictors of SLN metastases for patients with T2 melanoma. This prediction model can inform shared decision-making regarding whether to perform SLN biopsy for older patients with otherwise low-risk T2 melanoma.