Incidence and the risk factor of malignancy in Japanese patients with systemic sclerosis

To evaluate the incidence and risk factors for malignancy in Japanese patients with systemic sclerosis (SSc).

A cohort of 405 Japanese patients with SSc who visited Kitasato University hospital between 1973 and 2008 was analyzed retrospectively until the end of 2009. The incidence of malignancy was compared with that of the general population, with calculation of the standardized incidence ratio (SIR) and 95% confidence interval (CI).

The cohort represented 4,787 person-years of total disease duration after the diagnosis of SSc. Of 27 malignancies clinically found, lung cancer (n=10, 37%), especially adenocarcinoma, was the most frequent, followed by breast (n=4, 15%) or gastric (n=3, 11%) cancer. SSc patients with overlapping CTD tended to have less malignancy. Multivariable analysis revealed heart involvement of SSc as a significant risk factor for breast cancer (RR 8.2, 95% CI 1.2-72.8). Other than gastric cancer, the calculated SIRs of malignancies in SSc patients were above 1 (SIR of overall malignancy 1.24, 95% CI 0.77-1.71), even though only lung cancer had a significantly elevated incidence (SIR 5.73, 95% CI 2.18-9.29). Every patient with lung cancer had interstitial lung disease (ILD) and every autopsy performed on patients with lung cancer found a primary lesion of lung cancer in their ILD lesion (n=4).

Lung cancer was significantly frequent in SSc patients, which could develop on the basis of complicated ILD.