Desmoplastic melanoma: the role of radiotherapy in improving local control.

BACKGROUND: Desmoplastic melanoma (DM) is a rare subtype of cutaneous malignant melanoma reported to have a high local recurrence rate with surgical excision alone. The incidence of regional and distant metastasis is considered to be lower than traditional cutaneous melanoma, warranting more aggressive treatment of local disease. We conducted a retrospective analysis of patients with DM treated through the Princess Alexandra Hospital Melanoma Clinic to address the role of radiotherapy in the local control of this tumour.
METHODS: A review of a clinical database identified 24 patients between January 1997 and March 2006 with histopathologically confirmed DM who had received surgical excision as initial treatment followed by postoperative radiotherapy. All histopathology reports and radiotherapy treatment plans were reviewed. The primary outcome measure was 3-year in-field relapse-free survival.
RESULTS: There were 24 patients with 22 having a DM in the head and neck region. The median tumour thickness was 5.2 mm. The histopathological margin was less than 10 mm in 17 (71%) of patients. The 3-year in-field relapse-free survival was 91% (95% confidence interval 68.1-97.6%), the 3-year relapse-free survival was 86% (95% confidence interval 63.2-95.4%) with a 3-year overall survival of 83% (95% confidence interval 54.9-94.3%).
CONCLUSION: In a selected series of patients with DM with a high risk of local recurrence, adjuvant radiotherapy may have been effective in reducing the rate of local recurrence after surgical resection. A randomized trial is currently being developed to confirm this possible benefit.