Background: Variability in guideline compliance for melanoma lymph node surgery is partially attributable to controversy about patient selection. Prior data has indicated suboptimal practice of sentinel lymph node biopsy and undertreatment of clinically node-positive disease, predating Multicenter Selective Lymphadenectomy Trial II publication. To minimize bias, we studied compliance with lymph node surgery guidelines in T2/T3 (intermediate-thickness) melanoma patients, where the greatest agreement exists. Methods: T2/T3 and metastasis 0 melanoma cases were identified from 2004 to 2018 Surveillance, Epidemiology, and End Results data. Analysis used Cochran-Armitage test for trends, multivariable logistic regression, and Kaplan-Meier survival estimates. Results: Of 66,319 eligible T2/T3 patients, 57,211 were clinically node negative; 2,191 were clinically node positive; 6,197 were clinical node unreported; and 19,044/66,319 (28.8%) had no lymph node surgery. Among clinically node-negative patients, 36,433 (63.7%) underwent sentinel lymph node biopsy and 31,026 (85.2%) were pathologically node negative; 1,499 clinically node-positive patients (68.4%) had a lymph node dissection. Lymph node dissection rates declined from 2004 to 2018, 79.8% to 32.0% for clinically node-negative/pathologically node-positive patients and 80.4% to 61.2% for clinically node-positive/pathologically node-positive patients (both P < .0001). For clinically node-negative patients, lymph node surgery compliance improved from 63.7% (2004) to 70.4% (2018) (P < .0001). Compliance correlated with younger age, male sex, tumor mitotic rate, and site (extremity > trunk/head/neck) in multivariable analysis and improved 5-year cancer-specific survival (90.0% vs 83.4%) (all P < .0001). Conclusions: Despite clear guidelines, one-third of intermediate-thickness melanoma patients in a recent cohort did not have recommended lymph node surgery. Lymph node status is a key determinant of the relative benefit of adjuvant systemic therapy and the need for active surveillance of pathologically node-positive/clinically node-negative patients. These data highlighted a clinical care gap. Efforts to improve guideline compliance are a logical strategy to improve cancer outcomes for intermediate-thickness melanoma patients.
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