Incidence of Malignant Disease in Biopsy-Proven Inflammatory Myopathy: A Population-Based Cohort Study

Incidence of Malignant Disease in Biopsy-Proven Inflammatory Myopathy: A Population-Based Cohort Study

Rachelle Buchbinder, MBBS(Hons), MSc;
Andrew Forbes, PhD;
Stephen Hall, MBBS(Hons), BMedSci;
Xenia Dennett, PhD; and
Graham Giles, PhD, MSc

From Cabrini Medical Centre, Malvern, and Monash University, Melbourne University, and Cancer Control Research Institute of the Anti-Cancer Council of Victoria, Melbourne, Australia.

Abstract

Background: The validity and magnitude of an association between myositis and malignant disease continue to be debated. Such issues as the legitimacy of a myositis diagnosis and distinction among myositis subgroups in previous population-based studies remain unresolved.

Objective: To determine the risk for malignant disease in patients with biopsy-proven inflammatory myopathies.

Design: Population-based, retrospective cohort study.

Setting: Victoria, Australia.

Patients: 537 patients in whom a biopsy-positive idiopathic inflammatory myopathy was first diagnosed from 1981 through 1995.

Measurements: Standardized incidence ratios were calculated to compare the incidence of malignant disease in patients with inflammatory myopathy and the general population.

Results: A total of 116 cases of malignant disease were found in 104 patients. Seventy-four cases were identified concurrently with (within 7 days) or after diagnosis of myositis. The highest risk for malignant disease was associated with dermatomyositis (standardized incidence ratio, 6.2 [95% CI, 3.9 to 10.0]). The risk was also increased in polymyositis (standardized incidence ratio, 2.0 [CI, 1.4 to 2.7]), although the relative risk for malignant disease in dermatomyositis compared with polymyositis was 2.4 (CI, 1.3 to 4.2). An increased risk for malignant disease was also found in inclusion-body myositis (standardized incidence ratio, 2.4 [CI, 1.2 to 4.9]). The excess risk for malignant disease diminished with time (standardized incidence ratio, 4.4 [CI, 2.7 to 7.1] in the first year; 3.4 [CI, 2.3 to 5.1] between 1 and 3 years; 2.2 [CI, 1.3 to 3.9] between 3 and 5 years; and 1.6 [CI, 1.0 to 2.6] beyond 5 years [P for trend, 0.002]).

Conclusion: The risk for malignant disease is increased in biopsy-proven dermatomyositis and polymyositis and also appears to be increased in inclusion-body myositis.

Article and Author Information

Grant Support: By a grant from the Arthritis Foundation of Australia.
Requests for Single Reprints: Rachelle Buchbinder, MBBS (Hons), MSc, Suite 41, Cabrini Medical Centre, 183 Wattletree Road, Malvern, Victoria, Australia 3144; e-mail, rachelle.buchbinder{at}med.monash.edu.au.
Current Author Addresses: Dr. Buchbinder: Department of Clinical Epidemiology, Suite 41, Cabrini Medical Centre, 183 Wattletree Road, Malvern, Victoria, Australia 3144.
Dr. Forbes: Department of Epidemiology and Preventive Medicine, Monash University, Alfred Hospital Campus, Commercial Road, Prahran, Victoria, Australia 3181.
Dr. Hall: Suite 43, Cabrini Medical Centre, 183 Wattletree Road, Malvern, Victoria, Australia 3144.
Dr. Dennett: State Neuropathology Service, Department of Pathology, University of Melbourne, Parkville, Victoria, Australia 3010.
Dr. Giles: Cancer Epidemiology Centre and Victorian Cancer Registry, Cancer Control Research Institute of the Anti-Cancer Council of Victoria, 100 Drummond Street, Carlton South, Victoria, Australia 3053.
Author Contributions: Conception and design: R. Buchbinder, A. Forbes, S. Hall.
Analysis and interpretation of the data: R. Buchbinder, A. Forbes.
Drafting of the article: R. Buchbinder, A. Forbes.
Critical revision of the article for important intellectual content: R. Buchbinder, A. Forbes, S. Hall, X. Dennett, G. Giles.
Final approval of the article: R. Buchbinder, X. Dennett, G. Giles.
Provision of study materials or patients: R. Buchbinder, X. Dennett, G. Giles.
Statistical expertise: A. Forbes.
Obtaining of funding: R. Buchbinder.
Administrative, technical, or logistic support: R. Buchbinder, G. Giles.
Collection and assembly of data: R. Buchbinder, X. Dennett, G. Giles.