Skin Cancer

Skin cancers are the most common occurring malignancies. Basal cell carcinomas account for approximately 600,000 cases annually. There are numerous other types, including squamous cell, melanoma, merckel cell and adenoid cystic carcinoma. Radiation therapy is frequently used in the treatment of skin cancer, either as primary treatment, or as adjuvant therapy following surgery. It can be used for skin cancers on any part of the body, and is considered the treatment of choice for many tumors arising near the eye, ear, nose or lip since the cosmetic result achieved with radiation therapy is superior to surgical excision in these areas.

The decision of whether to use radiation therapy depends on the size of the lesion, location, histology and patient preference. Superficial skin cancers are treated with orthovoltage x-rays or electrons. Sometimes higher energy photons are required. An orthovoltage unit dedicated to treatment of superficial skin cancers is in place at the Valley Radiotherapy Associates' facility in Burbank.

Treatments are typically given daily for 4-6 weeks in order to achieve the best possible cosmetic result. Shorter treatment schedules are used on occasion.

Side effects of superficial radiation therapy are restricted to the skin. The area being treated becomes briskly red, similar to a sunburn, and can peel. Special creams and lotions are used as needed.

Basal Cell Carcinoma

Basal Cell skin cancers usually occur on sun-exposed areas and are most often seen in the elderly. The risk is increased in fair skinned individuals. They often appear as a raised area with central ulceration. These cancers rarely spread to other parts of the body but can be locally destructive if left untreated.

The cure rate with the use of radiation therapy for small lesions equals 95-98%, similar to surgery. Radiation is the treatment of choice when the lesion occurs on a part of the face that would likely become deformed if surgery were to be used. Examples include the eye lids, ears, nose or lip.

Squamous Cell Carcinoma

Squamous Cell cancers also commonly appear on sun-exposed areas of the skin. Certain chemicals have been identified as predisposing factors. Unlike basal cell carcinoma, they have the propensity to spread to neighboring lymph nodes and distant sites.

The principles of radiation are similar to those for the treatment of basal cell carcinoma. Radiation is again considered the treatment of choice for small lesions on certain parts of the face and neck.

Malignant Melanoma

The incidence of malignant melanoma is rising and also related to sun-exposure. The appearance of cutaneous melanoma is varied. Prognosis varies as well and is related to location, gender, size, thickness, level of invasion, growth pattern, age and the presence of involved lymph nodes.

Surgical excision is the mainstay of treatment. However, radiation therapy may be used in the post-operative setting in some instances. Radiation therapy can be used as primary therapy in special circumstances, for example, the lentigo maligna variety. Otherwise, it is usually used as adjuvant therapy. At M D Anderson Hospital, radiation therapy has been shown to decrease the incidence of a local-regional recurrence following surgery in some cases. Although melanoma is considered an inherently radioresistant tumor, its response to radiation has been demonstrated in the clinic, both as adjuvant therapy and in the palliation of symptoms of metastatic disease.

References:

1. Ang KK, Byers RM, Peters LJ, et al. Regional radiotherapy as adjuvant treatment for head and neck malignant melanoma. Arch Otolaryng H N Surg. 1990: 116: 169-172

2. Lovett RD, Perez CA, Shapiro SJ, et al. External irradiation of epithelial skin cancer. Int J Radiat Oncol Biol Phys 19:235-242, 1990

3. Million, R, Cassisi N. Eds. Management of Head and Neck Cancer, Ed. 2. Hagerstown, J. B. Lippincott Company, 1994.