Pilot Trial of Supplemental Vitamin A and Nicotinamide

Inclusion Criteria: 18 years old or greater; Either History of 2 or more histologically confirmed invasive cutaneous SCCs in the past 2 years or At least one previously billed Healthcare Common Procedure Coding System code 17004 (destruction of 15 or more benign or premalignant lesions of the integumentary system); Understands, reads, and writes English proficiently. Exclusion Criteria: Liver disease; Active peptic ulcer disease; Recent myocardial infarction; Hypotension; Internal malignancy within past 5 years; Renal impairment with eGFR<15 mL/min/1.73 m2; Being unable for follow up due to social reasons; Gorlin's syndrome or other genetic skin cancer syndrome; Huge number of current skin cancers; Metastatic SCC or invasive melanoma within the past 5 years; Pregnancy or lactation; Need for ongoing carbamazepine use (which could have a possible interaction with NAM); Use of acitretin or other oral retinoids within the past 6 months; Use of supplemental NAM, niacin, vitamin A, or beta carotene within the past 6 months; Field treatment for actinic keratoses (AKs) within the previous 4 weeks; Use of topical steroids.