Current evidence suggests that for melanomas with a thickness between 2 mm and 4 mm, the surgical margins need to be 2 cm or less.
The Intergroup Melanoma Surgical Trial compared 2-cm margins versus 4-cm margins for patients with 1-mm thick melanomas to 4-mm thick melanomas. With a median follow-up of more than 10 years, no significant difference was observed between the two groups in terms of local recurrence or survival. The reduction in margins from 4 cm to 2 cm was associated with a statistically significant reduction in the need for skin grafting (46% to11%; P < .001) and a reduction in the length of the hospital stay. Depending on the location of the melanoma, most patients can now have this surgery performed on an outpatient basis.
A study conducted in the United Kingdom randomly assigned patients with melanomas more than 2 mm in thickness to excision with either 1 cm margins or 3 cm margins. Patients treated with 1 cm margins of excision had a higher rate of local regional recurrence (hazard ratio [HR], 1.26; 95% confidence interval [CI], 1.00–1.59; P = .05), but no difference in survival was seen (HR, 1.24; 95% CI, 0.96–1.61; P = .1).
This suggests that 1 cm margins may not be adequate for patients with melanomas that are more than 2 mm in thickness. Few data are available to guide treatment in patients with melanomas more than 4 mm thick; however, most guidelines recommend margins of 3 cm whenever anatomically possible. Although prophylactic regional lymph node dissections (LNDs) have been used in patients with stage II melanomas, four prospective randomized trials have failed to show a benefit for this procedure in terms of survival.[4,5,6,7]
Lymphatic mapping and sentinel lymph node (SLN) biopsy have been used to assess the presence of occult metastasis in the regional lymph nodes of patients with stage II disease, which potentially identifies individuals who may be spared the morbidity of regional LND and individuals who may benefit from adjuvant therapy.[8,9,10,11,12] The diagnostic accuracy of SLN biopsy has been demonstrated in several studies with a false-negative rate of 0% to 2%.[8,13,14,15,16,17] Using a vital blue dye and a radiopharmaceutical agent, which are injected at the site of the primary tumor, the first lymph node in the lymphatic basin that drains the lesion can be identified, removed, and examined microscopically. If metastatic melanoma is detected, a complete regional lymphadenectomy can be performed in a second procedure. To ensure accurate identification of the SLN, lymphatic mapping and removal of the SLN should be performed prior to wide excision of the primary melanoma.
To date, no published data from prospective trials are available on the clinical significance of micrometastatic melanoma in regional lymph nodes, but some evidence suggests that for patients with tumors of intermediate thickness and occult metastasis, survival is better among those patients who undergo immediate regional lymphadenectomy than it is among those who delay lymphadenectomy until the clinical appearance of nodal metastasis. Because this finding arose from a post hoc subset analysis of data from a randomized trial, it should be viewed with caution.
The International Multicenter Selective Lymphadenectomy Trial (MSLT-1 [JWCI-MORD-MSLT-1193]) included 1,269 patients with intermediate-thickness (defined as 1.2 mm–3.5 mm in this study) primary melanomas. There was no melanoma-specific survival advantage (the primary endpoint) for those patients randomly assigned to wide excision plus SLN biopsy followed by immediate complete lymphadenectomy for node positivity versus patients randomly assigned to nodal observation and delayed lymphadenectomy for subsequent nodal recurrence at a median of 59.8 months.[Level of evidence: 1iiB]
This trial was not designed to detect a difference in the impact of lymphadenectomy in patients with microscopic lymph node involvement.