Radiotherapy for management of basal and squamous cell carcinoma

Abstract

More than 3.5 million cutaneous basal cell and squamous cell carcinomas are diagnosed per year in the United States, which is more than all other cancers combined. The incidence of cutaneous squamous and basal cell carcinoma is also increasing because of enhanced exposure to ultraviolet light or sunlight, a depleting ozone, changing clothing styles, and increasing longevity. These cancers are often excluded from cancer registries and as a result, they are underreported and their socioeconomic burden is underestimated. Fortunately, cutaneous basal cell and squamous cell carcinomas typically present a local, rather than distant, problem and are usually highly curable with local management. Cutaneous basal cell carcinomas arise from pleuripotent cells in the basal layer of the epidermis and tend to develop following sun exposure in childhood. Basal cell carcinomas often present as slow-growing translucent papules with raised, telangectatic borders on the head and neck. These tumors rarely metastasize to the regional lymph nodes (0.01%-0.5% of cases) although locally advanced lesions can invade nearby structures and cause symptoms such as numbness, pain, and weakness. In general, basal cell carcinomas have a low rate of growth of 5 mm or less per year and have a higher cure rate following local management than squamous cell carcinomas. In contrast, squamous cell carcinomas arise from epithelial keratinocytes and tend to progress over decades of sun exposure from precursor lesions known as actinic keratoses, which are typically small, red, scaly, 1-3 mm papules with rough texture. Cutaneous squamous cell carcinomas also can progress from squamous cell carcinoma in situ, which tends to occur later in life. Compared with basal cell carcinomas, squamous carcinomas have a higher risk of local recurrence (8%-15% of cases) and distant metastasis (0.5%-16% of cases). The risk of recurrence or metastasis with basal cell and squamous cell carcinoma is dependent on multiple risk factors.