MIAMI – The decision to perform sentinel lymph node biopsy in cutaneous melanomas with a Breslow depth of less than 1.0 mm should be based on histopathologic factors, findings from a series of 472 patients suggest.
Sentinel lymph node biopsy (SLNB) is important for staging and determining prognosis in thicker melanomas, but its role in thinner melanomas is more controversial. There is no clear consensus in the literature regarding which prognostic factors predict sentinel lymph node metastases in thin melanomas, Dr. Suzanne Berkman and her colleagues at the Washington (D.C.) Cancer Institute reported in a poster at the annual meeting of the American Academy of Dermatology.
In their series of patients who underwent SLNB between 1997 and 2008 at the institute, the investigators found Breslow depth, Clark level, and nodular subtype to be positively associated with SLNB positivity. Ulceration status was also associated with SLNB positivity, but this association did not reach statistical significance.
The mean Breslow depth of the melanomas in the study’s 472 patients was 2.11 mm. In all, 330 patients had a Breslow depth greater than 1.0 mm, and 142 had a Breslow depth of 1.0 mm or less (thin melanomas).
The American Joint Committee on Cancer recommends performing SLNB only on melanomas with a Breslow depth of 1.0 mm or greater with clinically uninvolved lymph nodes. The recommendation for thin melanomas is that SLNB be performed in those measuring less than 1.0 mm if there is ulceration and at least 1 mitosis per mm2 – particularly if Breslow depth is at least 0.75 mm.
The practice at the Washington Cancer Institute is to perform SLNB for all melanomas of a Breslow depth of at least 0.76 mm, and to biopsy those thinner than 0.76 mm that have adverse histopathologic factors, such as Clark level IV/V, ulceration, and high mitotic rate, the investigators reported. In their series, 55 patients with a mean Breslow depth of 3.26 mm had a positive SLNB.
Of the 330 patients with a Breslow depth greater than 1.0 mm, 16% had a positive SLNB, compared with only 2% of the 142 patients with thin melanomas. Mean Breslow depth in the patients in those groups with positive SLNB was 3.4 mm and 0.81 mm, respectively.
The rate of SLNB positivity in the study increased with increasing depth of invasion: In all, 2% of those with Breslow depth of 1.0 mm or less had a positive SLNB, compared with 10% of those with a depth of 1.01-2.0 mm, 23% of those with a depth of 2.01-4.00 mm, and 23% of those with a depth greater than 4.0 mm, the investigators noted.
Not only was positivity a function of Breslow depth, but Breslow depth correlated with disease progression and survival, as did SLNB positivity, the investigators found.
Local or distant recurrence occurred in 43 patients (9%) overall. Those with recurrence had a mean Breslow depth of 4.19 mm and a mean follow-up of 45 months. Only 17 of the 43 survived; they had a mean Breslow depth of 3.76 mm and a mean follow up of 58 months.
Of the 417 patients with a negative biopsy, 29 (7%) developed recurrence – including 1 with a thin melanoma – and 12 (3%) developed distant metastases. Of the 55 patients with a positive biopsy, 14 (25%) developed recurrence – including 1 with a thin melanoma – and 7 (13%) developed distant metastases. Death occurred in 4% of patients with a negative biopsy, compared with 16% of those with a positive biopsy.
“The results from our institution confirm the importance of SLNB on staging and prognosis in patients with cutaneous melanomas. We continue to perform SLNB in patients with thin melanomas and ulceration and high mitotic rate,” the investigators concluded.
The investigators reported no relevant disclosures related to the study.