Increased risk of malignancy in patients aged over 50 with idiopathic inflammatory myositis compared to patients with osteoarthritis of the knee

Abstract

Objectives: To estimate risk of malignancy in patients with idiopathic inflammatory myositis (IIM) compared to patients with knee osteoarthritis (OA).

Methods: Patients with IIM and knee OA aged over 50, who had no history of malignancy, were identified using Korean National claims database from January 2012 to December 2014. They had been observed until a malignancy was diagnosed or up to the end of the study, December 2015. The incidence rate (IR) of malignancy in IIM patients was calculated and compared with knee OA patients using standardized incidence ratio (SIR).

Results: A total of 634 polymyositis (PM) and 556 dermatomyositis (DM) patients were included. Overall, 100 solid (IR 270.4/10,000 person-years (PY), 95% confidence interval (CI) 217.4–323.4) and 12 hematologic malignancies (IR 32.4/10,000 PY, 95% CI 14.1–50.8) occurred. Compared with knee OA, risk of overall (SIR 1.5, 95% CI 1.2–1.8), solid (SIR 1.4, 95% CI 1.1–1.6), and hematologic malignancy (SIR 5.7, 95% CI 2.5–9.0) were increased in IIM patients. This was due to increased incidence of malignancy in DM (hematologic malignancy, SIR 8.7, 95% CI 2.7–14.7, solid malignancy, SIR 1.5, 95% CI 1.1–1.9).

Conclusion: Patients with IIM, especially DM, have an increased risk of malignancy compared to patients with knee OA.

Keywords:

• Neoplasm
• myositis
• dermatomyositis
• polymyositis

Author contributions

HK, YKS, DHY, and SKC contributed the study design, data analysis, and writing of the manuscript. SC, SGI, SYJ, EJJ had substantial contributions to the acquisition, statistical analysis, and interpretation of data. Also, all of the authors were involved in drafting the article or revising it critically for important intellectual content and final approval of the version to be submitted.

Ethics approval

This study was approved by the institutional review board (IRB) of Hanyang University Medical Center and was exempt from an IRB review because we used existing, publicly available data and the information of the subjects could not be identified directly or through identifiers linked to the subjects (IRB file No. HYUH 2017-09-009).

Informed consent

Informed consent was waived because we utilized a de-identified database which was opened to the public.

Conflict of interest

None.

Additional information

Funding

This research was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea [Grant Number: HC17C0082].