Risk of malignancy in scleroderma: A population-based cohort study

Objective To determine the incidence of cancer in patients with scleroderma (systemic sclerosis) and to compare those rates with cancer rates in the local population. Methods Cancer risk in scleroderma patients in the Detroit metropolitan area was assessed by linking patient identification codes of the Michigan Scleroderma Registry to the Metropolitan Detroit Cancer Surveillance System database. Patients were screened between the years 1973 and 2002, with additional followup to 2004. Standardized incidence ratios (SIRs) were calculated for selected malignancies (lung, liver, colon, breast, cervical, and prostate cancers, and non-Hodgkin's lymphomas), with stratification by sex and race. Results Of 934 patients in the Scleroderma Registry, 538 were included in the study based on tri-county residency (436 females and 102 males). Of these, 45 first malignancies were noted (37 females and 8 males). Lung cancer (10 cases) was found to be the most common cancer in scleroderma patients. However, its incidence was not significantly different from that in the general population of metropolitan Detroit (SIR 1.23). Other types of cancer were examined, and no significant differences were found as compared with the rates in the local population, with 1 exception: black females with scleroderma had significantly higher rates of liver cancer (SIR 45.8). Conclusion Contrary to previous studies, this study did not find statistical evidence of an increased incidence of cancer in scleroderma patients, except for liver cancer. One possible reason is the high background rates of certain cancers in the metropolitan Detroit area. It may be necessary to consider local cancer rates when comparing different scleroderma cohorts.