Critical evaluation of sentinel lymph node biopsy in pT1b and pT2a melanoma patients: A nationwide population-based study

Introduction

Sentinel lymph node biopsy (SLNB) aims to stage patients. According to the 8th edition of the American Joint Committee on Cancer(AJCC) staging manual, patients with pT1b or pT2a melanoma can be eligible for adjuvant immunotherapy, however, only if they have a sentinel node (SN) tumour burden > 1 mm. This study aims to determine the percentage of patients with pT1b or pT2a that will become eligible for adjuvant immunotherapy following SLNB.

Methods

A nationwide, population-based study was conducted using data from the Dutch Pathology Databank. Patients diagnosed with pT1b and pT2a melanoma between 2002 and 2023 were included. The primary endpoint was the number of SNs with a tumour burden > 1 mm.

Results

We identified 36,606 patients of who 16,042 underwent SLNB. SN positivity was 5 % for patients with pT1b melanoma, and 11 % for pT2a melanoma. A tumour burden > 1 mm was found in 1.5 % and 4.1 %, translating to a number needed to treat (NNT) of 69 for pT1b and 25 for pT2a.

Conclusion

This nationwide study demonstrated a low incidence of positive SNs and minimal likelihood of significant clinical outcomes following SLNB. Given the high NNT to be eligible for adjuvant immunotherapy, SLNB may no longer be justified for pT1b melanoma. For patients with pT2a melanoma, SLNB should be considered carefully, balancing limited clinical benefits against potential risks.