Chapter 46: Radiation Therapy

SUMMARY

• Radiation is an effective nonsurgical therapy that provides long-term disease control and a cure for squamous cell and basal cell skin cancer. Typically used radiation modalities include low-energy x-rays, brachytherapy, and electrons with a bolus, which target superficial skin and minimize doses to deeper normal tissues.

• Radiation can be used for small tumors on the face with excellent cosmesis. Nonsurgical patients with nonmelanoma skin cancers can also be treated with radiation.

• Radiation is recommended as adjuvant treatment in patients with high-risk features, such as large tumor size, deeply invasive disease, incomplete excision, high-grade lesions, perineural invasion, lymphovascular invasion, and immunosuppression, as well as cases of lymph node involvement.

• The role of radiation therapy (RT) in melanoma is decreasing because of the increased use and efficacy of targeted agents and immunotherapy. Adjuvant radiation should be used for high-risk features such as desmoplastic disease, bulky disease, multiple lymph nodes, and extracapsular extension. Hypofractionation should be considered, depending on the site of disease.

• Radiation also has a role in the management of Merkel cell carcinoma, primary cutaneous lymphoma, cutaneous angiosarcoma, Kaposi sarcoma, and extramammary Paget disease.

DON’T FORGET

• Avoid RT in patients with predispositions for developing skin cancer (basal cell nevus syndrome) and connective tissue disorders affecting the skin (scleroderma).

• Radiation with BRAF inhibitors increases toxicity and can lead to serious side effects.

CLINICAL PEARLS

• Choosing the correct technique of radiation is based on the location and depth of disease. Brachytherapy and superficial RT are only effective on superficial lesions and should be used cautiously. Tumors thought to have deeper invasion should be considered for electrons and high-energy photons.

• Patients with cancer with high-risk features such as nodal involvement, large size, perineural invasion, lymphovascular space invasion, or close margins should be referred for adjuvant radiation after surgery.

• Hypofractionated regimens can be delivered with equivalent control while minimizing the number of treatments, though cosmesis may be less optimal.

• Margins around the tumor must account for any microscopic extent of disease, beam characteristics, and setup reproducibility.

PATIENT EDUCATION POINTS

• Patients and caregivers should be educated that frequently reported side effects of RT are fatigue and skin irritation, which may include desquamation. However, with appropriate supportive care, including skin cream and antibacterial medication, skin will heal quickly with excellent cosmesis.

• Cosmesis after radiation is usually excellent; however, patients may have residual changes in pigmentation or telangiectasias. Severe late side effects such as fibrosis and secondary cancers are rare.