Radiation Treatment Field Delineation for Axillary Metastases from Malignant Melanoma

Article Outline

• Purpose/Objective(s)
• Materials/Methods
• Results
• Conclusions
• Copyright

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Purpose/Objective(s) 

To compare the outcome and treatment-related toxicity for patients with axillary lymph node metastases from malignant melanoma treated with surgery and postoperative radiation therapy (RT) to either the axilla only or both the axilla and supraclavicular fossa (extended field, EF), with or without systemic therapy.

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Materials/Methods 

The medical records of 200 consecutive patients treated with postoperative RT for axillary lymph node metastases from malignant melanoma between 1984 and 2005 were retrospectively reviewed. All patients underwent a level I-III axillary dissection and postoperative RT to a median dose of 30 Gy at 6 Gy/fraction delivered twice weekly; 95 patients received RT to the axilla only (48%), and 105 patients received RT to the EF (52%). High-risk features that were indications for RT included: lymph node metastasis size ≥3 cm (n = 139), ≥4 positive lymph nodes (n = 91), extracapsular nodal extension (n = 166), recurrent disease (n = 37), or multiple factors (n = 141).

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Results 

At a median follow-up of 59 months (range 5.9 - 283), 111 patients (56%) had relapsed, and 99 patients (50%) had died. The median overall survival was 76.3 months. The 5-year overall survival, disease-free survival, and distant metastasis-free survival rate was 51%, 43%, and 46%, respectively. The 5-year axillary control (AC) rate was 88%. On univariate analysis, only >2 positive lymph nodes predicted for decreased AC (p = 0.04). On multivariate analysis, both >2 positive lymph nodes (p = 0.02) and lymph node size ≥6 cm predicted for decreased AC (p = 0.03). Only 3 of the 95 patients (3%) who received RT to the axilla only field experienced a recurrence in the ipsilateral supraclavicular fossa. None of the patients treated with the EF experienced a supraclavicular relapse. There was no difference in the 5-year AC rates based on the treated field (89% for axilla only vs. 86% for EF; p = 0.4). Forty-seven patients (24%) developed RT-related complications, including 42 (21%) with lymphedema. Patients treated with the axilla only field had a lower rate of complications at 5 years than those treated with the EF (27% vs. 39%; p = 0.047). On both univariate and multivariate analyses, only the treatment with EF irradiation was significantly associated with increased RT-related complications.

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Conclusions 

Adjuvant hypofractionated RT to the axilla for metastatic malignant melanoma with high-risk features is a highly effective method of controlling axillary disease, with a 5-year axillary control rate of 88%. Limiting the radiation field to the axilla only produced equivalent axillary control rates to EF (comprising both the axilla and supraclavicular fossa). Furthermore, limiting the RT field was significantly associated with a lower RT-related complication rate.