In their article on radiotherapy for cutaneous malignant melanoma, Drs. Ballo and Ang discuss four key points, which we will address below.
Adjuvant Irradiation of the Primary Site
The authors advocate adjuvant irradiation of the primary tumor site after surgical excision of the tumor in cases of desmoplastic melanoma, locally recurrent disease, Breslow thickness > 4 mm combined with ulceration or satellitosis, and positive margins where re-resection might compromise cosmesis. Guidelines published by dermatologic societies recommend treating higher-risk tumors by more extensive surgery, including wider safety margins.[1,2] According to the UK guidelines, radiotherapy for lentigo maligna may be appropriate in particular clinical situations.
We would extend the indication for radiotherapy to all facial melanomas up to 1 mm thick in patients aged 60 years and older. If extensive surgery is not possible due to the extent of the lesion, comorbidities, unacceptable functional or cosmetic results, or refusal of the patient, radiotherapy may be used as an alternative.[ 3,4] However, adjuvant radiotherapy following appropriate surgery is not included in the traditional guidelines.[ 1,2] This is probably due to the belief that the complete removal of the melanoma by wide local excision can be histologically controlled and that insufficient results may be corrected by re-resection.
Is this supposition correct, and are the suggestions of Ballo and Ang therefore not justified? Some melanomas including desmoplastic and neurotropic variants may grow in scattered small units with wide spaces in between. Despite negative margins, the excision may therefore be incomplete. The histopathologist needs to identify such tumors with an elevated risk of local recurrence. As suggested by Ballo and Ang, adjuvant radiotherapy may decrease the recurrence rate of these tumors.
An elevated local recurrence rate must also be expected in cases of satellitosis. In these cases, however, new metastases may develop at the margins of the irradiated areas and grow into the fields regardless of how wide the radiotherapy safety margins are. Surgery in irradiated tissue is more difficult and produces less favorable results.
Local recurrences indicate that surgery has failed and may be problematic in these cases. A critical consideration of a second treatment should include the possibility of radiotherapy.
Adjuvant Irradiation of the Lymph Node Basins
We and others have found no improvement in overall survival with adjuvant irradiation of the lymph node basins after dissection of the lymph nodes.[5-8] We have observed regional failure in 8 of 58 irradiated patients vs 12 of 58 nonirradiated patients. Most regional recurrences among the irradiated patients occurred in the presence of metastases at other sites. Tumor cells from these other metastases may have reseeded the irradiated area where recurrences were usually found in the skin and subcutis, and in only one patient, in a lymph node. We have not recommended adjuvant radiotherapy for lymph node basins except for recurrent regional lymph node metastasis.
Ballo and Ang emphasize that the regional failure rate is increased due to at least one of the following risk factors: extracapsular extension, at least four involved lymph nodes, lymph nodes ≥ 3 cm, cervical lymph node location, and recurrent nodal disease. A decreased local recurrence rate following adjuvant radiotherapy has been reported by the authors and others for groups with a higher percentage of patients with risk factors.[7,8] Ballo and Ang recommend adjuvant radiotherapy if at least one risk factor is present and a therapeutic (not elective) lymph node dissection has been performed. We think that this proposal is justified, and our previous recommendations should therefore be modified.
Elective Irradiation of Regional Nodes
When there is no clinically evident nodal disease after tumor excision, the authors advocate elective nodal irradiation for melanomas of Clark level ≥ IV or a Breslow thickness ≥ 1.5 mm, especially for head and neck cancer patients who are not candidates for systemic therapy or regional dissection. We can use sentinel lymph node biopsy as a relatively efficient staging procedure with low morbidity.[ 9] Patients who, by this procedure, have a substantially reduced probability of lymph node involvement and later disease progression can be selected. For these patients, the proposed adjuvant radiotherapy would constitute overtreatment. We generally suggest starting no adjuvant therapy without prior evaluation of the sentinel lymph nodes.
Positive Sentinel Lymph Node
We agree with Ballo and Ang that the role of completion lymphadenectomy and therapeutic irradiation after detection of a positive sentinel lymph node needs to be determined in a future trial.
Financial Disclosure: The authors have no significant financial interest or other relationship with the manufacturers of any products or providers of any service mentioned in this article.