Table 5.
Clinical and preclinical studies, grade of recommendation, and level of evidence regarding different oral photoprotectors in the prevention of nonmelanoma skin cancer.
| Molecule | Studies Regarding Skin Cancer Prevention | Grade of Recommendation * | Level of Evidence * | |||||
|---|---|---|---|---|---|---|---|---|
| Preclinical Studies | Case Reports/Series | Observational Studies | Randomized Controlled Trials | Systematic Reviews/Meta-Analyses | Efficacy in Prevention of NMSC | |||
| Nicotinamide | + | − | − | + | − | + | A | 1b |
| β-Carotene | + | − | − | + | − | − | D | 1b |
| Vitamin D3 | + | − | + | − | + | − | D | 5 |
| Astaxanthin | + | − | − | − | − | − | D | 5 |
* From the Centre for Evidence-Based Medicine, https://www.cebm.ox.ac.uk/resources/levels-of-evidence/oxford-centre-for-evidence-based-medicine-levels-of-evidence-march-2009 (accessed date: 30 December 2020). “+” means presence of studies while “−“ means no studies regarding that kind of research.