Abstract
IMPORTANCE: Autoimmune skin diseases (ASDs) and cancer both involve immune system dysregulation, with ASDs characterized by heightened immune activity, and cancer associated with immune evasion; however, their impact on cancer prognosis remains unclear. OBJECTIVE: To investigate the association of ASDs with cancer prognosis and survival outcomes after antineoplastic treatment in patients with cancer. DESIGN, SETTING, AND PARTICIPANTS: This population-based cohort study used data from Taiwan's Nationwide Cancer Registry and National Health Insurance Database to evaluate survival outcomes in patients with cancer who received antineoplastic treatment (ie, chemotherapy, targeted therapy, or immunotherapy) between January 1, 2019, and June 30, 2021. Data were analyzed from July 2023 to April 2025. EXPOSURES: ASDs, including alopecia areata, Sjögren syndrome, vitiligo, cutaneous lupus erythematosus, psoriasis, lichen planus, autoimmune bullous diseases, systemic sclerosis, morphea, hidradenitis, and dermatomyositis. MAIN OUTCOME AND MEASURES: All-cause mortality and cancer-specific mortality were assessed during the follow-up period. To account for potential confounding, both inverse probability of treatment weighting (IPTW) and propensity score matching strategies were applied. Cox proportional hazards regression models were applied to estimate hazard ratios (HRs) for all-cause mortality, while the Fine-Gray hazard model was used to estimate subdistribution HRs (SHRs) for cancer-specific mortality, with noncancer-related deaths considered as competing events. RESULTS: Of 197 895 patients included in the analysis, 26 008 were in the ASD group (mean [SD] age, 64.0 [13.3] years; 14 969 female [57.6%]) and 171 887 were in the non-ASD group (mean [SD] age, 62.8 [13.0] years; 80 525 female [46.9%]). Patients with ASDs had significantly better survival outcomes than those without ASDs, with an IPTW-adjusted HR of 0.94 (95% CI, 0.92-0.96) for all-cause mortality and an SHR of 0.94 (95% CI, 0.92-0.96) for cancer-specific mortality. These associations remained consistent in propensity score-matched analyses. Among ASD subtypes, alopecia areata and Sjögren syndrome were consistently associated with lower mortality risk. CONCLUSIONS AND RELEVANCE: This population-based cohort study found that patients with ASDs had significantly better cancer survival outcomes than those without ASDs. This finding suggests that there is a potential immunological association between ASDs and cancer prognoses, highlighting the need for further investigation into the underlying mechanisms and the implications for oncologic management.