The intriguing effect of delay time to sentinel lymph node biopsy on survival: a propensity score matching study on a cohort of melanoma patients

Background: Time between primary melanoma excision and sentinel lymph node biopsy (SLNB) has not been sufficiently studied as an independent predictor of survival in cutaneous melanoma. Objectives: We used propensity score matching to evaluate whether early SLNB (performed <= 40 days from excisional biopsy) is associated with higher mortality in patients with cutaneous melanoma. Materials & methods: A retrospective cohort study at a tertiary melanoma referral centre. We included 787 consecutive patients from the melanoma database of the Instituto Valenciano de Oncologia who underwent a SLNB between 1st January 2000 and 31st December 2015, of whom 350 were matched into pairs using propensity score matching. The variable of interest was the time between primary melanoma excision and SLNB (<= 40 days vs > 40 days). The study outcomes were disease-free survival (DFS), melanomaspecific survival (MSS), and overall survival (OS). Results: A delay time of 40 days or less was associated with worse DSF (adjusted hazard ratio [AHR]: 1.68; 95% confidence interval [CI]: 1.07-2.65; p = 0.024), MSS (AHR: 2.06; 95% CI: 1.1-3.53; p = 0.08), and OS (AHR: 1.77; 95% CI: 1.11-2.83; p = 0.017). Other variables associated with shorter MSS were age, tumour location and thickness, mitotic rate, and SLN status. Conclusion: Early SLNB was associated with worse survival in patients with cutaneous melanoma after adjusting for classic prognostic factors. A delay time of over 40 days was not associated with higher mortality.