Real-World Evidence vs. Meta-Analyses: The Evolving Debate on Nicotinamide for Skin Cancer Chemoprevention

The clinical utility of oral nicotinamide (NAM) for non-melanoma skin cancer (NMSC) chemoprevention remains a prime example of the tension between landmark RCT data, real-world evidence (RWE), and systematic evidence syntheses.

While the 2015 Phase 3 ONTRAC trial established a 23% reduction in new NMSCs among high-risk patients (Damian et al., NEJM), subsequent meta-analyses and recent large-scale observational data have triggered a nuanced methodological debate.

The New Evidence Landscape

1. The VA Corporate Data Warehouse Cohort (JAMA Dermatol, Nov 2025): Breglio et al. conducted a massive retrospective cohort study of 33,822 US veterans. Utilizing propensity score matching, the authors found an overall 14% reduction in skin cancer risk with oral nicotinamide (500 mg, twice daily for >30 days). Strikingly, when initiated early—after a first skin cancer diagnosis—the risk reduction rose to 54%. However, this benefit declined when treatment was initiated after multiple subsequent malignancies. Among solid organ transplant recipients (SOTRs), no overall significant risk reduction was observed, though early use trended with reduced cutaneous squamous cell carcinoma (cSCC) incidence. (Source: JAMA Dermatol. 2025;161(11):1140-1147. doi:10.1001/jamadermatol.2025.3238)

2. The Meta-Analytic View (Nutrients): Conversely, a systematic review and meta-analysis by Tosti et al. pooled data across immunocompetent and immunosuppressed cohorts, concluding that current pooled evidence is insufficient to demonstrate a statistically significant reduction in NMSC incidence (BCC RR: 0.88, 95% CI: 0.50-1.55; SCC RR: 0.81, 95% CI: 0.48-1.37). (Source: Nutrients. 2024;16(1):100. doi:10.3390/nu16010101)

3. Methodological Critique (Am J Clin Dermatol, March 2026): In a critical appraisal titled “Nicotinamide for Skin Cancer Chemoprevention: The Jury Was Out and Still Is,” Tan and Williams challenge the optimism of the 2025 VA study. They highlight significant vulnerability to residual unmeasured confounding, immortal time bias, exposure misclassification, and limited external validity given the demographic skew of the VA population. (Source: Am J Clin Dermatol. 2026;27(2):209-215. doi:10.1007/s40257-025-01005-y)

The HEOR & Clinical Takeaway

From a biological standpoint, NAM’s mechanism is compelling: it prevents UV-induced ATP depletion, replets cellular NAD+ stores, and enhances energy-dependent DNA repair pathways while mitigating UV-induced immunosuppression.

However, from an evidence-generation perspective, this timeline underscores a classic challenge:

• RCTs demonstrate efficacy under tightly controlled, high-risk conditions.

• Large-scale RWE suggests strong real-world effectiveness, particularly if introduced as an early intervention.

• Critical Appraisals & Meta-analyses remind us that retrospective observational data must be interpreted with extreme caution due to structural biases.

While the “jury is still out” on routine, widespread clinical adoption for all patient types, oral NAM remains an inexpensive (~$10/month), highly tolerable option for high-risk individuals. The key moving forward will be refining patient selection—identifying precisely who benefits most, and at what stage of their oncological history.

#Dermatology #Oncology #RealWorldEvidence #SkinCancer #ClinicalResearch #HEOR #Epidemiology