Frei, M.D., Noreen R. Kamal, M.D., Walter J. Montanera, M.D., Alexandre Y. Poppe, M.D., C.M., Karla J. Ryckborst, R.N., Frank L. Silver, M.D., Ashfaq Shuaib, M.D., Donatella Tampieri, M.D., David Williams, M.B., Ph.D., Oh Little Bang, M.D., Ph.D., Blaise W. Baxter, M.D., Paul A. Burns, M.B., Ch.B., M.D., Hana Choe, M.D., Ji-Hoe Heo, M.D., Ph.D., Christine A. Holmstedt, D.O., Brian Jankowitz, M.D., Michael Kelly, M.D., Ph.D., Guillermo Linares, M.D., Jennifer L. Mandzia, M.D., Ph.D., Jai Shankar, M.D., Sung-Il Sohn, M.D., Richard H. Swartz, Ph.D., Philip A. Barber, M.B., Ch.B., M.D., Shelagh B. Coutts, M.B., Ch.B., M.D., Eric E. Smith, M.D., M.P.H., William F. Morrish, M.D., Alain Weill, M.D., Suresh Subramaniam, M.D., Alim P. Mitha, M.D., John H. Wong, M.D., Mark W. Lowerison, M.Sc., Tolulope T.Participants were also excluded if they had had metastatic tumor, invasive melanoma, or an internal malignant condition in the last 5 years. Study Procedures We randomly assigned participants in a 1:1 ratio to receive either 500 mg of nicotinamide twice daily or matched placebo. Nicotinamide and placebo were administered in similar coated tablets. Individuals received either nicotinamide or placebo for 12 months, and adherence was monitored by two of the authors who counted the remaining tablets at each go to through 12 months. Skin-cancer tumor checks were performed by dermatologists, who had been unacquainted with the study-group assignments, at baseline and at visits at 3-month intervals for 1. 5 years. Detected lesions that didn’t warrant biopsy were monitored at subsequent visits immediately, and if indeed they were found to become malignant on biopsy later on, the date of their initial detection was assigned as the date of detection for analyses.