Cancer risks of dermatomyositis and polymyositis: a nationwide cohort study in Taiwan
- Equal contributors
1 Department of Dermatology, National Yang-Ming University, No. 155, Sec. 2, Linong Street, Taipei 112, Taiwan
2 Department of Dermatology, Taichung Veterans General Hospital, No. 160, Sec. 3, Chung-Kang Road, Taichung 40705, Taiwan
3 Department of Internal Medicine, National Yang-Ming University, No. 155, Sec. 2, Linong Street, Taipei 112, Taiwan
4 Department of Gastroenterology, Taichung Veterans General Hospital, No. 160, Sec. 3, Chung-Kang Road, Taichung 40705, Taiwan
5 Institute of Public Health, China Medical University, No. 91 Hsueh-Shih Road, Taichung 40402, Taiwan
6 Department of Dermatology, Taipei Veterans General Hospital, No. 201, Sec. 2, Shih-Pai Road, Taipei 112, Taiwan
Arthritis Research & Therapy 2010, 12:R70 doi:10.1186/ar2987Published: 16 April 2010
The association of idiopathic inflammatory myositis (IIM) and malignancies has been reported, but rarely in Asian countries. Our aim was to investigate the risk of cancer among IIM patients without a prior history of malignancies, in Taiwan.
We conducted a nationwide cohort study of 1,012 patients with dermatomyositis (DM) and 643 patients with polymyositis (PM), but without prior history of malignancies, utilizing the National Health Insurance Database from 1997 to 2007. Standardized incidence ratios (SIRs) of cancers were analyzed.
A total of 95 cancers (9.4%) in DM and 33 cancers (4.4%) in PM were identified. Overall cancer risk was significantly elevated in DM patients (SIR = 5.11, 95% confidence interval [CI] = 5.01 to 5.22) and PM patients (SIR = 2.15, 95% CI = 2.08 to 2.22). Most cancers were detected in the first year of observation. The risk of cancer decreased with observation time, yet remained elevated compared with the general population in both study groups after 5 years of follow-up. DM was associated with sustained elevated risk of cancers in every age group, whereas the risk of cancer in PM was highest in younger patients and decreased with age. DM patients were at the greatest risk of cancers of the nasopharynx, lungs and hematopoietic malignancies.
Patients with IIM are at increased risk for cancer and should receive age-appropriate and gender-appropriate malignancy evaluations, with additional assessment for nasopharyngeal, lung and hematologic malignancy following diagnosis, and with continued vigilance for development of cancers in follow-up.