Effects of time interval between primary melanoma excision and sentinel node biopsy on positivity rate and survival

Background Sentinel node biopsy (SNB) is essential for adequate melanoma staging. Most melanoma guidelines advocate to perform wide local excision and SNB as soon as possible, causing time pressure. Objective To investigate the role of time interval between melanoma diagnosis and SNB on sentinel node (SN) positivity and survival. Methods This is a retrospective observational study concerning a cohort of melanoma patients from four European Organization for Research and Treatment of Cancer Melanoma Group tertiary referral centres from 1997 to 2013. A total of 4124 melanoma patients underwent SNB. Patients were selected if date of diagnosis and follow-up (FU) information were available, and SNB was performed in <180 d. A total of 3546 patients were included. Multivariable logistic regression and Cox regression analyses were performed to investigate how baseline characteristics and time interval until SNB are related to positivity rate, disease-free survival (DFS) and melanoma-specific survival (MSS). Findings Median time interval was 43 d (interquartile range [IQR] 29–60 d), and 705 (19.9%) of 3546 patients had a positive SN. Sentinel node positivity was equal for early surgery (≤43 d) versus late surgery (>43 d): 19.7% versus 20.1% (p = 0.771). Median FU was 50 months (IQR 24–84 months). Sentinel node metastasis (hazard ratio [HR] 3.17, 95% confidence interval [95% CI] 2.53–3.97), ulceration (HR 1.99, 95% CI 1.58–2.51), Breslow thickness (HR 1.06, 95% CI 1.04–1.08), and male gender (HR 1.58, 95% CI 1.26–1.98) (all p < 0.00001) were independently associated with worse MSS and DFS; time interval was not. Interpretation No effect of time interval between melanoma diagnosis and SNB on 5-year survival or SN positivity rate was found for a time interval of up to 3 months. This information can be used to counsel patients and remove strict time limits from melanoma guidelines.