Background: Cutaneous melanoma (CM) is the deadliest form of skin cancer. Genetic factors explain a substantial proportion of CM risk (twin h2 = 58%), underscoring the potential importance of polygenic risk scores (PRS) in capturing inherited susceptibility and improving identification of individuals at high risk. However, much of the genetic architecture underlying melanoma remains unexplained. Larger genome-wide association studies (GWASs) enable the discovery of new risk loci and improve PRS estimation, strengthening their potential use in precision prevention and early detection strategies to manage melanoma better.
Methods: We performed an expanded European-ancestry meta-analysis by combining 35 GWASs from 29 cohorts across Australia, the United States, Canada and Europe. In total, the analysis included 69,871 cases and 1,616,233 controls, more than doubling the previous sample sizes. We further conducted a multi-trait GWAS analysis (MTAG) incorporating correlated melanoma risk factors, including nevus count, pigmentation-related traits, telomere length and vitiligo, to expand the discovery of risk loci. We constructed a new PRS from this larger GWAS meta-analysis using SBayesRC and validated it in independent cohorts from the US (AllofUS, PLCO) and Australia (QSkin).
Results: The meta-analysis identified 116 independent CM risk loci, including 51 of the 54 previously known loci. MTAG adds 25 additional candidate loci, with concordant effects in replication (r = 0.70, 95% CI 0.43-0.86, P = 8.7×10-5). Among novel signals, we observe hits within or near several cancer-related genes NOTCH2, MDM4, TP63, PIK3CA, and CDKN1B, as well as the immune-related HLA-A region. The new PRS improves discrimination over the baseline model that includes age, sex, and PCs (principal components) of genetic ancestry (AUC increase of 0.06-0.09) across independent validation datasets. Overall predictive performance reaches an AUC of 0.70, indicating robustness across populations with different ultraviolet exposure profiles.
Conclusion: This expanded genetic analysis substantially improves both locus discovery and performance of melanoma PRS. The results support the potential use of PRS for melanoma risk stratification and targeted screening, particularly in early detection settings.