New Perspectives in the Pharmacological Treatment of Non-Melanoma Skin Cancer

Non-melanoma skin cancers are the most common malignancy in humans, with a basal/squamous cell carcinoma incidence ratio of 4:1 in immunocompetent patients. Basal cell carcinoma rarely metastasizes but commonly causes significant local tissue destruction and disfigurement, whereas squamous cell carcinoma is associated with a substantial risk of recurrence and metastasis; the prognosis in metastatic patients is poor. Surgical approaches give a cure rate greater than 90% if appropriately applied, on the basis of the characteristics of the primary tumors and of the patients, but in selected cases, medical treatment (5-fluorouracil, imiquimod, diclofenac and, more recently, ingenol mebutate) is preferable to invasive procedures and provides a good chance of cure, with generally excellent cosmetic outcomes. In case of advanced and metastatic non-melanoma skin cancer, newly developed molecularly targeted therapy represents a reasonably promising alternative to classical cytostatics. In particular, the monoclonal antibody cetuximab, directed against the epidermal growth factor receptor, is effective and well-tolerated in squamous cell carcinoma patients. Moreover, the recent identification of mutations in the Hedgehog signaling pathway in basal cell carcinoma lead to the development of the smoothened Hedgehog pathway inhibitor vismodegib, that was recently approved for the treatment of locally advanced or metastatic basal cell carcinoma. In this review we provide an overview of the molecular pathways involved in NMSC pathogenesis, focusing on the mechanisms of action, indications, efficacy, side effects and contraindications of new medical treatments that specifically tackle molecular targets of these pathways.