E328: Sentinel Lymph Node Biopsy in Thin Melanoma: Is It Necessary?

Introduction: Melanoma is the most lethal skin malignancy. The prognostic value of a sentinel lymph node biopsy (SLNB) for staging in intermediate melanoma is demonstrated; however, it remains unclear for thin melanoma (Breslow depth = 0.8-1.0 mm). Currently, nodal positivity rates of thin melanomas are reported at 5-13%⁵, however some studies suggest it even lower.¹⁰ National Comprehensive Cancer Network recommends discussing SLNB with patients, however the “decision not to perform a SLNB may be based on patient comorbidities, preference, or other factors.” The purpose of this study was to gather evidence to aid surgeons and patients in making informed decisions regarding SLNB.

Methods: Retrospective data collected on adults 18 years and older with stage TIb melanoma excision and SLNB between 1/1/2015-12/31/2020. Data included demographics, tumor and nodal characteristics, and surgery. Exclusion criteria included melanoma thickness > 1.0 mm, metastatic/in-transit disease, clinically positive lymph nodes, recurrent melanoma, and melanoma of the head or neck.

Results: Of 704 eligible patients, 141 were included (20%) in this cohort; median age of 60 years, 54.6% female, 48.2% with comorbidities, 75.9% with superficial spreading melanoma, 5% with ulceration. Median melanoma thickness was found to be 0.9 mm and a median mitotic rate of 1 per mm². Of SLNB, 74.5% were axillary and 25% were groin biopsies (median 2 nodes). Positive nodes found in 4 patients (2.8%), among which macrometastases were found in 3 (75%) and micrometastases in 1 (25%). 20.6% of patients had a post-operative complication.

Conclusions: This 2.8% positive lymph node rate is lower than reported in the current literature. Our data indicates that sentinel lymph node biopsies may not be necessary in patients with thin melanoma. This study provides surgeons treating thin melanomas with the opportunity to make informed decisions regarding SLNB versus active surveillance. Additionally, this data helps provide patients with accurate information to assist them in making informed decisions regarding their surgical care and management.