Factors Predicting for Local Control in Patients With Desmoplastic Melanoma

Abstract

Desmoplastic melanoma (DM) is a rare variant of melanoma that may be locally aggressive. The purpose of this review was to elucidate risk factors for local failure after wide local excision of DM. Two hundred ninety patients who were diagnosed with DM between 1989 and 2010 were retrospectively identified after approval by the IRB. Histopathologic variables, including perineural invasion (PNI), patient demographics, and details regarding surgery and radiation therapy were recorded. All available cases were reviewed internally and classified pure versus mixed DM per the Memorial Sloan Kettering Cancer Center system. The incidence of local recurrence as first site of recurrence was recorded. Median age (range) was 68 (16-96) years and 213/290 (73%) were men. Median Breslow depth (range) was 3.9 (0.5-35.0) mm. Radiation therapy (RT) was delivered to 115 patients (40%), among which 100 cases (87%) were to the primary site alone. RT was given with electrons alone in 83/115 (72%) patients. Hypofractionation (n = 55, 48%) (6 Gy times 5 fractions every 72 hrs) and conventional fractionation (n = 47, 41%) were both utilized. RT was more likely to be delivered in thicker (>4 mm), head and neck location, Clark's level V, ulcerated primaries, and with positive margins (all p < 0.05). Overall 37/290 (13%) patients developed local failure as the first site of failure. 17% (24/144) patients with PNI developed local failure versus ≤9% for those without PNI, although p = 0.14. Seventeen percent of patients (28/168) who did not receive radiation recurred versus 7% (8/115) for those who received RT (p = 0.02, OR = 2.7, 95% CI: 1.2-6.1). On multivariable analysis (MVA) with age and Breslow's thickness dichotomized using their medians, location (OR = 3.08, 95% CI: 1.15-8.30 for head and neck versus trunk and extremities), RT (OR = 8.08, 95% CI: 2.62-24.96 for no RT vs. RT) and Clark's level (OR = 4.0, 95% CI: 1.47-10.87 for V vs. others) were significant for local recurrence. On MVA, RT was one of the factors significant for relapse-free survival with a hazards ratio of 3.1 for no RT versus RT (p < 0.0001). DM may be a locally recurrent and aggressive variant of malignant melanoma. Adjuvant radiation therapy may be useful in selected cases in order to improve local control after surgical excision.