Sentinel node biopsy in patients with melanoma improves the accuracy of staging when added to clinicopathological features of the primary tumor

It has been claimed, without supporting evidence, that knowledge of sentinel node (SN) status does not provide more accurate prognostic information than basic clinicopathological features of a primary cutaneous melanoma. We sought to investigate this claim and to quantify any additional value of SN status in predicting survival outcome. Data for a Dutch population-based cohort of melanoma patients (n = 9272) and for a validation cohort from a large Australian melanoma treatment center (n = 5644) were analyzed. Patients were adults diagnosed between 2004 and 2014 with histologically-proven, primary invasive cutaneous melanoma who underwent SN biopsy. Multivariable Cox proportional hazards analyses were carried out in the Dutch cohort to assess recurrence-free survival (RFS), melanoma-specific survival (MSS) and overall survival (OS). The findings were validated using the Australian cohort. Discrimination (Harrell's C-statistic), net benefit using decision curve analysis and net reclassification index (NRI) were calculated. The Dutch cohort showed an improved C-statistic from 0.74 to 0.78 for OS and from 0.74 to 0.76 for RFS when SN status was included in the model with Breslow thickness, sex, age, site, mitoses, ulceration, regression and melanoma subtype. In the Australian cohort, the C-statistic increased from 0.70 to 0.73 for OS, 0.70 to 0.74 for RFS and 0.72 to 0.76 for MSS. Decision curve analyses showed that the 3-year and 5-year risk of death or recurrence were more accurately classified with a model that included SN status. At 3 years, sensitivity increased by 12% for both OS and RFS in the development cohort, and by 10% and 6% for OS and RFS, respectively, in the validation cohort. Knowledge of SN status significantly improved the predictive accuracy for RFS, MSS and OS when added to a comprehensive suite of established clinicopathological prognostic factors. However, clinicians and patients must consider the magnitude of the improvement when weighing up the advantages and disadvantages of SN biopsy for melanoma. •The additional prognostic information provided by sentinel node biopsy in melanoma patients is poorly documented.•This study quantified and validated the additional prognostic value of SN status over basic clinicopathological features.•Survival models that included SN status showed a statistically significant improvement in predictive accuracy.•The sensitivity of 3-year overall survival predictions was increased by 10%-12% by determining