Nicotinamide for secondary keratinocyte carcinoma prevention in solid organ transplant recipients.

Nicotinamide has many well-established chemopreventive properties in protecting against ultraviolet-induced skin damage, mitigating inflammation, and reducing keratinocyte carcinoma (KC) development among immunocompetent individuals. Its effectiveness in immunosuppressed patients, however, is unclear. There is conflicting research on whether nicotinamide effectively decreases KCs in immunosuppressed solid organ transplant recipients (SOTRs). This study assesses the effectiveness of nicotinamide in the secondary prevention of KC in immunosuppressed patients. We conducted a retrospective cohort study in a single tertiary care institution. The primary outcome was KC incidence in the year before and after nicotinamide supplementation. Secondary outcomes included the incidence of invasive squamous cell carcinoma (SCC), SCC in situ (SCCis), and basal cell carcinoma (BCC) over one- and two-year intervals. All included patients had taken oral nicotinamide, 500 milligrams twice daily, for at least one year. A total of 47 SOTRs (74.5% male; mean age 65.2 years) were included in our retrospective cohort study. Of 81 patients initially screened, 34 were excluded due to inadequate follow-up, dermatologic care outside our institution, or early discontinuation of nicotinamide. At one year post-nicotinamide supplementation, total KC incidence decreased from 224 (78 SCC, 103 SCCis, 43 BCC) to 121 cases (40 SCC, 55 SCCis, 26 BCC), a mean reduction of 2.19 KCs (95% CI: -3.48 to -0.90; p = 0.0012). Significant reductions were observed in SCC (mean decrease of 1.15; 95% CI: -1.78 to -0.52; p = 0.00081) and SCCis (mean decrease of 1.37; 95% CI: -2.61 to -0.13; p = 0.032). BCC reduction was not statistically significant (p = 0.13). In the 31 patients with two-year follow-up data, KC incidence declined from 234 to 167, a mean reduction of 2.18 KCs (95% CI: -4.18 to -0.14; p = 0.037). Sensitivity analyses excluding patients on concomitant acitretin confirmed that reductions in total KC incidence maintained significance at both one-year and two-year intervals. Nicotinamide supplementation significantly decreased KC incidence in immunosuppressed SOTRs over the one-year and two-year intervals. We recommend nicotinamide as a low-risk, low-cost chemopreventive supplement for reducing KCs in SOTRs.