What is the role of radiotherapy in the treatment of melanoma?

Role of Radiotherapy in Melanoma Treatment

Radiotherapy is not indicated as a primary treatment for operable melanoma that can be excised with adequate margins, but should be considered for palliative treatment of symptomatic metastases, particularly brain and bone metastases, and in cases of inadequate resection margins of lentigo maligna melanoma or when re-excision is not feasible. 1

Primary Treatment of Melanoma

• Surgery remains the standard treatment for localized primary melanoma, with excision margins determined by the Breslow thickness of the tumor 1
• There is no indication for radiotherapy in operable melanoma that has been excised with adequate margins 1
• For lentigo maligna (melanoma in situ), the standard treatment is surgical excision with a margin of 0.5 cm 1, 2

Specific Indications for Radiotherapy

Lentigo Maligna Melanoma

• Radiotherapy should be considered in cases of inadequate resection margins of lentigo maligna melanoma when re-excision is not feasible 1
• For elderly patients or when complete excision is impossible or contraindicated, radiotherapy is a valid alternative to surgery 1, 2

Regional Nodal Disease

• After complete nodal dissection, there is no indication for adjuvant radiotherapy 1
• Radiotherapy is an option in cases of incomplete nodal clearance, such as with fixed nodes, extensive invasion, or capsular disruption 1

Metastatic Disease

• Palliative radiotherapy should be considered especially for symptomatic brain or localized bone metastases 1
• For non-resectable in-transit metastases or inoperable primary tumors of the limbs without additional metastases, radiation therapy may be used, although there are limited data showing positive effects on outcome measures 1

Efficacy of Radiotherapy in Melanoma

• Approximately 23% of melanoma patients should receive at least one course of radiotherapy during the course of their disease 3
• Complete response rates vary by stage: 64% in UICC IIB (primary/recurrent lesions), 44% in UICC III (lymph node/in-transit metastases), and 17% in UICC IV (distant metastases) 4
• Patients achieving complete response with radiotherapy have significantly longer survival (median 40 months) compared to those without complete response (median 10 months) 4

Radiotherapy in Combination with Other Therapies

• Radiotherapy combined with newer systemic therapies, particularly immunotherapy, shows promise but is still being actively evaluated 5
• Current evidence does not conclusively support an abscopal response (regression of untreated metastases) when combining radiation with immunotherapy 6

Practical Considerations

• For palliative treatment, conventional radiotherapy with 2-6 Gy fractions to a median total dose of 48 Gy is commonly used 4
• Higher total radiation doses (above 40 Gy) are associated with better response rates and improved survival 4
• UICC stage is the most important independent prognostic factor for response to radiotherapy 4

Common Pitfalls to Avoid

• Underestimating the extent of lentigo maligna, particularly on the face, can lead to incomplete excision and recurrence 2
• Overreliance on radiotherapy as primary treatment when surgery with adequate margins is feasible 1
• Failure to consider radiotherapy for palliation in advanced disease, particularly for symptomatic brain or bone metastases 1