Age-related prognostic disparities in cutaneous melanoma: A population-based study and validated interactive web-based nomogram for individualized prognostic stratification.

BACKGROUND: Cutaneous melanoma (CM) in older adults (≥65 years) has distinct clinicopathological features and poorer survival than in younger adults. We evaluated age-related cancer-specific survival (CSS), prognostic associations, and an interactive web-based nomogram. METHODS: We analyzed 47,684 SEER patients (28,739 younger and 18,945 older adults). The independent Southwest Hospital cohort (n = 288) was used only for external validation. Propensity-score matching (1:1) compared age groups, and inverse-probability treatment weighting evaluated registry-coded histological and treatment associations. Prognostic factors from multivariable Cox regression were incorporated into a nomogram. The older SEER cohort was split 7:3 into training (n = 13,261) and internal-validation (n = 5684) sets. Training area-under-the-curve values were evaluated by 10-fold cross-validation. RESULTS: After matching (12,859 patients per age group), older adults had lower CSS. Weighted analyses associated acral lentiginous and nodular subtypes, local or unrecorded surgery, and no recorded sentinel lymph-node biopsy with poorer observed survival. The nomogram showed consistent discrimination and calibration in the training, internal-validation, and external-validation cohorts. CONCLUSIONS: Older adults had poorer CSS, particularly with advanced stage and aggressive histology. The externally validated nomogram integrates routinely available clinicopathological variables and supports individualized prognostic communication and surveillance planning. Further calibration and competing-risk validation will strengthen its clinical applicability.