Incidence of Cancer in Morphea and Systemic Sclerosis

Importance Systemic sclerosis (SSc) is associated with increased risk of cancer, but population-level data on cancer risk in morphea remain limited and conflicting. Objective To compare the incidence and standardized incidence ratios (SIRs) of overall and site-specific cancers in patients with morphea and SSc compared with the general population, and to identify factors associated with incident cancer. Design, Setting, and Participants This is a retrospective, population-based cohort study using linked administrative health databases (1996-2019) from Quebec, Canada, with follow-up through December 31, 2020. Patients were identified using published diagnostic algorithms requiring at least 2 billing claims with relevant International Classification of Diseases, Ninth Revision, and/or International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, codes at least 2 months apart, with specialist diagnosis or hospitalization. Data were analyzed from June 2025 to June 2026. Exposures Diagnosis of morphea or SSc. Main Outcomes and Measures Incident cancers were ascertained through linkage to the provincial cancer registry. SIRs were calculated with respect to the general population using Canadian Cancer Registry rates. Cumulative incidence was estimated using Fine-Gray competing risk methods; associated factors were evaluated with multivariable Cox regression. Results There were 6181 patients with morphea (median [IQR] age at diagnosis, 56 [40-68] years; 4605 female [74.50%]; 71 221.53 person-years of follow-up) and 8133 patients with SSc (median [IQR] age at diagnosis, 58 [48-69] years; 6530 female [80.29%]; 71 844.36 person-years of follow-up). During follow-up, 782 patients with morphea (12.65%) and 1104 with SSc (13.57%) developed cancer. Overall cancer incidence was increased in both the morphea (SIR, 1.24; 95% CI, 1.14-1.35) and SSc (SIR, 1.37; 95% CI, 1.27-1.48) cohorts. Solid tumor risk was elevated in both cohorts (morphea SIR, 1.17; 95% CI, 1.06-1.29; SSc SIR, 1.21; 95% CI 1.11-1.32). Hematologic cancer risk was markedly elevated in patients with SSc (SIR, 2.40; 95% CI, 1.92-2.96) but not statistically significant for those with morphea (SIR, 1.34; 95% CI, 0.97-1.81). Female reproductive and breast cancers predominated in the morphea group; lung cancer was most frequent among patients with SSc. Younger patients carried the highest relative risk. Immunosuppressant use was associated with lower cancer risk in patients with morphea (hazard ratio, 0.56; 95% CI, 0.46-0.68) and those with SSc (hazard ratio, 0.63; 95% CI, 0.55-0.70). Conclusions and Relevance This cohort study found that morphea and SSc were associated with increased cancer incidence compared with the general population, with distinct cancer profiles between the 2 conditions. These findings identify patients with morphea, like those with SSc, as a population warranting oncologic attention; whether disease-specific or intensified screening is beneficial requires further study.