Radiotherapy influences local control in patients with desmoplastic melanoma

Abstract

Background: Desmoplastic melanoma may have a high risk of local recurrence after wide excision. The authors hypothesized that adjuvant radiotherapy (RT) would improve local control in patients with desmoplastic melanoma, resulting in at least a 10% absolute decrease in local recurrence rate.

Methods: A total of 277 patients from 1989 through 2010 who were treated for nonmetastatic desmoplastic melanoma by surgery with or without adjuvant RT were reviewed. Clinicopathologic and treatment variables were assessed with regard to their role in local control.

Results: A total of 113 patients (40.8%) received adjuvant RT. After a median follow-up of 43.1 months, adjuvant RT was found to be independently associated with improved local control on multivariable analysis (hazards ratio, 0.15; 95% confidence interval, 0.06-0.39 [P<.001]). Among 35 patients with positive resection margins, 14% who received RT developed a local recurrence versus 54% who did not (P=.004). In patients with negative resection margins, there was a trend (P=.09) toward improved local control with RT. In patients with negative resection margins and traditionally high-risk features, including a head and neck tumor location, a Breslow depth >4 mm, or a Clark level V tumor, RT was found to significantly improve local control (P< .05). The data from the current study would suggest that patients who would be good candidates for omitting RT included those with negative resection margins, a Breslow depth ≤ 4 mm, and either no perineural invasion present or a non-head and neck tumor location.

Conclusions: RT for desmoplastic melanoma was independently associated with improved local control. Patients with positive resection margins or deeper tumors appeared to benefit the most from RT, whereas selected low-risk patients can safely omit RT.

Keywords: control; desmoplastic; local neoplasm recurrence; melanoma; radiation; radiotherapy.

Figure 1

Kaplan-Meier plots for local control are shown in patients with desmoplastic melanoma (Top) who were treated with or without adjuvant radiotherapy (RT) (277 patients) and (Bottom) who were with or without positive resection margins (272 patients; excluding 5 patients with unknown resection margin status). Post-op indicates postoperative.

Figure 2

Breakdown of patients with desmoplastic melanoma (DM) treated with or without adjuvant radiotherapy and their corresponding Kaplan-Meier (KM) 5-year actuarial local control (LC) and crude LC rates with log-rank P values is shown. Patients with negative resection margins, a non-head and neck tumor location, and a Breslow depth ≤ 4 mm had a < 5% benefit with radiotherapy.