Combination chemoprevention with diclofenac, calcipotriol and difluoromethylornithine inhibits development of non-melanoma skin cancer in mice

Background/Aim: With increasing incidence of nonmelanoma skin cancer (NMSC), focus on chemoprevention of this disease is growing. The aim of this study was to evaluate topical combination therapies as chemoprevention of UV radiation-induced tumors in a mouse model. Materials and Methods: A total of 160 SKH-1 mice were randomized to one placebo group and four chemoprevention groups (diclofenac plus difluoromethylornithine; diclofenac plus calcipotriol; difluoromethylornithine plus calcitriol; and diclofenac plus difluoromethylornithine plus calcipotriol). The mice received UVB radiation for 20 weeks followed by 17 weeks with topical application of chemoprevention. The number of mice with tumors, number of tumors per group and tumor area size were compared using a linear regression model. Results: Chemoprevention with diclonefac plus calcipotriol and diclonefac plus difluoromethylornithine had a significant inhibiting effect on the number of tumors per group and the area of tumors. Moreover, diclonefac plus difluoromethylornithine had a significant inhibiting effect on the number of mice with tumors. Conclusion: Potentially, nonmelanoma skin cancer in humans may be prevented with these agents with few adverse effects. Therefore, clinical studies are needed to determine their therapeutic/preventive effect and possible adverse effects.