INTRODUCTION
The incidence of non-melanoma skin cancer (NMSC) in the United States is approximately 5 million annual cases per year.1 While surgery is the gold standard for the management of NMSC, radiotherapy is an alternative therapy for patients who are not good surgical candidates. Radiotherapy is also a valuable adjuvant treatment to surgery for aggressive NMSC including those with perineural invasion. In this review, the applications of radiotherapy for NMSC are highlighted.Indications for RadiationNMSC, including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), are treated through various modalities including conventional surgical excision, Mohs micrographic surgery, cryotherapy, curettage and electrodessication, topical imiquimod or 5-fluorouracil, photodynamic therapy, and radiation. Before the advent of Mohs micrographic surgery, radiotherapy was a commonly utilized therapeutic approach in the management of NMSC with which most dermatologists were familiar.2 Now, according to National Comprehensive Cancer Network recommendations, radiotherapy can be performed as a primary treatment when the patient has a contraindication to surgery or if the location of cancer is in a cosmetically sensitive area, such as the eyelid, ear, or nose that may lead to disfigurement. Also, radiotherapy can act as an adjunct to surgery in cases where there is a high likelihood of residual tumor such as in large tumors with positive margins, cases involving perineural, lymph node, or parotid gland invasion, or cases with multiple recurrences.3 The American Academy of Dermatology (AAD) position statement on the use of superficial radiation therapy and electronic surface brachytherapy states that although surgical management remains the most effective treatment for BCC and SCC, superficial radiation therapy and electronic surface brachytherapy can be secondary treatment options in situations during which surgical intervention is contraindicated or refused.4-5 Radiotherapy has shown to be efficacious for the treatment of BCC and SCC with 5-year recurrence rates of 8.7% and 10% respectively.6-7 In high-risk sites such as the lip, treatment of SCC with radiation has a 90% 5-year recurrence-free survival rate.8 For select patients with perineural invasion, local control approaches 100% with postoperative radiotherapy.9 In patients with cutaneous SCC with metastasis to lymph nodes, the combined approach of surgery with radiotherapy appears to be most optimal. In one study, patients treated with both surgery and radiotherapy for cutaneous SCC with metastasis to the lymph nodes had a 20% local recurrence rate and 73% 5-year disease-free survival rate as compared to 43% local recurrence rate and 54% 5-year disease-free survival in surgery alone patients.10 Another study examining patients with cutaneous SCC
