Next day sentinel node biopsy for melanoma after lymphoscintigraphy using ^99mTc-labelled nanocolloid does not adversely affect long-term outcomes

Sentinel Lymph Node Biopsy (SLNB) is an important management tool for early-stage melanoma. Different radiopharmaceuticals are used internationally to localise the sentinel node using lymphoscintigraphy (LSG) before surgery. Recent reports have suggested that a delayed interval between LSG and SLNB using ^99mTc-labelled nanocolloid tracer has an adverse survival impact, but not with ^99mTc-labelled antimony sulphide colloid. This study aims to analyse survival outcome in a prospective cohort of melanoma patients undergoing same day or next day SLNB after LSG using ^99mTc-labelled nanocolloid.

Outcome data were reviewed for patients undergoing SLNB, stratified by time interval between LSG and SLNB at a single UK academic centre. Kaplan–Meier survival analysis was used to assess overall survival (OS), melanoma-specific survival (MSS) and progression-free survival (PFS). Cox multivariable regression analysis identified independent risk factors.

925 patients had LSG using the ^99mTc-nanocolloid tracer between 2009 and 2019, with a median follow-up of 6.36 years. No difference was seen on univariate analysis in OS, MSS, PFS, or nodal recurrence between patients undergoing same day or next day SLNB (Log-rank P = 0.437, 0.293, 0.587, 0.342 respectively). In addition, nodal recurrence as first site or anytime site of recurrence in SLNB negative patients was similar between the groups (Log-rank P = 0.093 and 0.457 respectively). Stratified analysis of time did not demonstrate an outcome difference (MSS Log-rank P = 0.938). Cox multivariable regression did not show time interval to independently influence OS, MSS or PFS.

We do not find a significant effect on long-term outcomes when SLNB is performed the day after LSG with ^99mTc-labelled nanocolloid tracer. We infer that tracer migration is not clinically significant within 24 h of injection based on long term clinical outcome data.