Study Suggests Which Melanoma Patients May Avoid Sentinel Node Biopsy

Most patients with newly diagnosed melanoma undergo a sentinel lymph node biopsy (SLNB), in which the sentinel lymph nodes are removed and examined to find whether the cancer has spread beyond the skin. Now, results from a large cohort study indicate that a proportion of stage pT1b-pT2a melanoma patients could potentially avoid SLNB. The findings were presented at the Society of Surgical Oncology 2021 International Conference on Surgical Cancer Care (abstract 59).

“The results of this large cohort study would suggest that, with the new modern treatment paradigm, a proportion of pT1b-pT2a patients could potentially avoid SLNB, since the management of these patients may remain unchanged, regardless of sentinel node status,” said lead study author Marc Moncrieff, MD, FRCS, a plastic surgeon from Norfolk & Norwich University Hospital, in Norwich, England.

In the study, Dr. Moncrieff and his colleagues identified 3,515 patients from nine cancer centers in five countries with American Joint Committee on Cancer (AJCC) 8th edition stage IB primary cutaneous melanoma. They analyzed patient demographics, primary tumor characteristics, SLNB status/details and their association with survival outcomes.

The outcomes of the Multicenter Selective Lymphadenectomy Trial-2 and DeCOG studies, in addition to the maturation of data from recent adjuvant systemic therapy trials, have established the role of SLNB for accurately staging cutaneous melanoma patients, while simultaneously shifting the treatment paradigm from identifying patients for surgical management of the regional lymph nodes to identifying those eligible for adjuvant systemic therapy (N Engl J Med 2017;376:2211-2222; J Clin Oncol 2019;37[32]:3000-3008). Adjuvant systemic therapy is usually not routinely recommended for AJCC IIIA melanoma. Those pT1b-pT2a melanoma patients who are SLNB-positive are mostly mapped to AJCC IIIA, which brings into question the role of SLNB for these patients.

The overall SLNB-positive rate was 11.5%. Virtually all node-positive patients (99.5%) were AJCC IIIA. The 0.1-mm difference in mean Breslow thickness between the positive and negative biopsies was significant but not clinically relevant (P<0.001). A mitotic rate of 2 mm² or greater identified 67.5% of all SLNB-positive patients and 74.0% of all stage N2 to N3 and/or extracapsular spread. The incidence of a mitotic rate of 2 mm² or greater was 55.8%. A mitotic rate of 2 mm² or greater was the only significant, independent predictor of relapse-free, distant disease–free, nodal relapse–free and disease-specific survival on multivariate analysis (hazard ratios, 3.78, 3.35, 4.11 and 2.98, respectively; P<0.0001 for all).

Dr. Moncrieff said the role of SLNB for a mitotic rate of 1 mm² or lower may merit further clarification.

“This is a very interesting study of this common subgroup of patients with stage IB cutaneous melanoma, and it has been presented by excellent investigators globally,” said Craig L. Slingluff Jr., MD, the Joseph Helms Farrow Professor of Surgery and co-leader of the Cancer Therapeutics Program at UVA Cancer Center, in Charlottesville, Va.

“The finding that mitotic rate of 2 mm² or greater identifies most of those with positive nodes does raise an interesting question of whether these clinical stage IB melanomas with one mitosis or less could be spared SLNB. Factors that need to be considered are the interobserver variation in mitotic rate assessment, and the fact that some patients with stage IIIA melanoma are offered adjuvant therapy on clinical trials.”

Dr. Slingluff is also the director of the Human Immune Therapy Center at the University of Virginia.

This article is from the July 2021 print issue.