Pilot Trial of Supplemental Vitamin A and Nicotinamide

Who May Qualify: - 18 years old or greater; - Either History of 2 or more diagnosed by tissue sample (biopsy-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. Who Should NOT Join This Trial: - 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. Always talk to your doctor about whether this trial is right for you.