Radiotherapy for Lentigo Maligna Melanoma
Abstract & Commentary
Source: Schmid-Wendtner MH, et al. J Am Acad Dermatol 2000;43:477-482.
The most important therapeutic part of melanoma treatment is adequate surgical excision. Randomized clinical trials have shown the importance of larger surgical margins as the Breslow’s depth increases. For many melanomas that occur on the face, the required wide local excision may result in unacceptable cosmetic or functional morbidity. An alternative would be the use of radiation therapy.
In this report from Germany, 22 patients with lentigo maligna melanoma were treated with radiation therapy. The patients’ ages ranged from 58 to 87 years old (median 76) of whom 86% were female. Although sites of involvement included the eyelid, nose, scalp, or ear, the most common site was the cheek (45%). The Breslow’s depth ranged from 0.1 to 10 mm with a median of 0.35 mm.
Treatment consisted of surgical excision of the nodular part of the lesion. The remaining lentiginous part of the lesion was then radiated using a direct field and a 0.5 to 2.0 cm safety margin of clinically normal skin. The total dose was 100 Gy given in 10 fractions and the treatment was given with a 14.5 kv machine. The study also included 42 patients successfully radiated for benign lentigo maligna, not otherwise discussed herein.
Patients were treated between 1987 and 1998 with a mean follow-up time of 23 months. Nineteen of the 22 patients with melanoma remained in complete remission. Two patients had a local recurrence after 13 and 44 months, both of whom were successfully salvaged by surgical excision. The last patient developed pulmonary metastases 44 months after therapy with no evidence of a local failure. This patient’s melanoma was 3.6 mm deep. Cosmetic results were described as good or excellent in all patients. No serious complications were seen.
COMMENT by Kenneth W. Kotz, MD
Of the different clinical subtypes of melanoma, lentigo maligna melanoma is the least common, accounting for 5% of melanoma lesions.1 Compared with other subtypes, it also presents later in life with a mean age of diagnosis in the eighth decade.1 It is typically located on the nose, cheeks, or temples and may have been present for years in the precursor form, lentigo maligna. However, prognosis and treatment are no different than any similarly staged melanoma.
Even with the use of Moh’s surgery, the proximity of facial melanomas to critical structures may preclude surgical intervention. Thus, this report of long-term control with the use of radiation therapy is welcome. Of note, there is no reason why primary treatment with radiation therapy could not be preceded by a sentinel lymph node biopsy, if indicated. However, readers of Clinical Oncology Alert may recall the recent discussion of the unique problems which occur when a sentinel node biopsy is attempted in patients with melanoma of the head and neck.2
Although complete surgical excision remains the standard of care, this series of 22 cases of lentigo maligna melanoma demonstrates that fractionated radiotherapy may be a reasonable alternative to surgery in locations of cosmetic or functional importance. Of course, the good results may be related in part to the underlying excellent prognosis of these early stage patients, most of whom had stage I or II disease. The relatively nonpenetrating radiation used in this study deposits half of its intensity by the time the beams have penetrated only 1 mm of tissue.3 With a relative sparing of the normal tissues located only a few millimeters deep, this approach may work more through the desquamation of several layers of cells rather than direct radiotoxicity.3
More conventional radiation would involve electron beams with 6-18 MeV rather than the 14.5 kv orthovoltage radiotherapy used in this study. Furthermore, conventional treatment in the United States with megavoltage equipment implies a somewhat lower total dose, and dose per fraction. As might be expected, high rates of control with lentigo maligna melanoma have been reported with conventional treatment.3 Altogether, the report by Schmid-Wendtner demonstrates that radiation therapy is a safe and effective alternative for melanoma of the head and neck, in particular lentigo maligna melanoma, when surgical excision cannot be performed.
References
1. Langley R. In: Balch C, et al, eds. Cuteaneous Melanoma. 3rd ed. St. Louis, Mo: Quality Medical Publishing; 1998:81-101.
2. Kotz K. Clinical Oncology Alert 2000;4:26-27.
3. Cooper J. Hematol Oncol Clin North Am 1998;12:849-863.
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