Recent Advances in Clinical Research for Skin Cancer Chemoprevention

Simple Summary Skin cancer is the most common cancer type in the United States and the world. Both non-melanoma and melanoma skin cancer show a clear association with overexposure to solar ultraviolet radiation. Chemoprevention is an appealing strategy to control the increasing rate of skin cancer. Since the target population for cancer chemoprevention is healthy individuals with high cancer risk, pharmacological agents that can be used for preventive purposes should be both effective and safe. The present review outlines the current state of skin cancer chemoprevention clinical trials, in terms of study populations, agents, outcomes (including cancer risk reduction), predictive biomarkers, and adverse reactions. The most studied agents include non-steroidal anti-inflammatory drugs, retinoids, 5-fluorouracil, and nicotinamide. The route of administration can be oral or topical. Since the trial outcomes for most of these agents are inconsistent, there is a need for additional research in this area. Neoplasm arising from the keratinocytes or melanocytes in the skin is the most prevalent type of cancer in the United States and worldwide. Since ultraviolet (UV) radiation may be a causing factor for several types of skin cancer, effective strategies to manage skin cancer include preventive measures such as minimizing exposure to UV and applying sunscreens. However, the effect of sunscreen in reducing skin cancer incidence remains uncertain. An alternative approach to prevent skin cancer is chemoprevention, which is defined as using either natural products or synthetic compounds to inhibit, delay, or reverse the development of cancer. Preclinical studies have demonstrated the effectiveness of multiple pharmacological agents and dietary supplements. However, whether preclinical findings can be translated into clinical application is unknown. This review evaluates the state of recent clinical trials investigating chemopreventive agents focusing on skin cancer to compare the target populations, interventions, endpoints, and outcomes of these trials. The ClinicalTrials and PubMed databases were searched for their available literature using the key words "skin cancer" and "chemoprevention". The objective of this review is to provide updated information on the effectiveness and side effects of promising chemopreventive agents in human subjects and to identify research gaps.