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ABSTRACT & COMMENTARY
Synopsis: Dermatomyositis and polymyositis are uncommon disorders that have been reported to be associated with increased risk for malignancy. In this population-based study using published data from three Scandinavian countries, 198 and 137 cancers were shown to occur in 618 dermatomyositis and 914 polymyositis patients, respectively. The malignant diseases most strongly associated with dermatomyositis were ovarian, lung, gastric, colorectal and pancreatic cancers, and non-Hodgkin’s lymphoma. The risk of lung and bladder cancers and non-Hodgkin’s lymphoma was also increased in patients with polymyositis.
Source: Hill CL, et al. Lancet 2001;357:96-100.
The association of dermatomyositis, and to a lesser extent polymyositis, has been appreciated for several decades,1 but there have not been published series large enough to identify the specific cancer types involved. Thus, Hill and colleagues performed a pooled analysis of published national data from Sweden, Denmark, and Finland. All patients with dermatomyositis and polymyositis were identified by discharge diagnoses from the Swedish Board of Health (1964-1983), Danish Hospital Discharge Registry (1977-1989), and Finnish National Board of Health (1969-1985). These cases were matched with the national cancer registries to identify the cases of cancer that developed up to 1985 in Sweden, 1995 in Denmark, and 1997 in Finland, and to the death registries in each country for the same period. Standardized incidence ratios (SIR) for specific cancer types were calculated.
From this, 618 cases of dermatomyositis were identified, and in this cohort 198 had cancer. After the diagnosis of dermatomyositis, 115 of the 198 developed cancer. Thus, the disease was strongly associated with malignancy (SIR, 3.0, 95%; CI, 2.5-3.6), particularly ovarian (10.5, 6.1-18.1), lung (5.9, 3.7-9.2), pancreatic (3.8, 1.6-9.0), stomach (3.5, 1.7-7.3), and colorectal (2.5, 1.4-4.4) cancers and non-Hodgkin’s lymphoma (3.6, 1.2-11.1).
There were 914 cases of polymyositis and 137 of these had cancer (95 after the diagnosis of polymyositis). Thus, the risk of cancer was increased in this group, but to a lesser extent than with dermatomyositis. In this group the SIR for non-Hodgkin’s lymphoma was 3.7 (1.7-8.2), and lung cancer (2.8, 1.8-4.4), and bladder cancer (2.4, 1.3-4.7).
Hill et al conclude that in patients with dermatomyositis the risk of cancer of a wide range of types (particularly ovarian and lung cancer) is high. The association of cancer with polymyositis remains more modest. With either disorder, the risk of malignancy is highest at the time of myositis diagnosis.
COMMENT by William B. Ershler, MD
Dermatomyositis is an uncommon disorder and the evaluation of a large series of patients has not been possible. However, this type of analysis of registry data, which may only be possible in health care systems such as those in Scandinavia, can be very instructive. This report confirms the association of dermatomyositis (and to a lesser extent, polymyositis) with malignancy. Furthermore, the association is with a wide range of tumor types, including ovarian, lung, gastric, pancreatic, colorectal, and non-Hodgkin’s lymphoma. The tumor types that develop might be different for other ethnic groups. For example, nasopharyngeal carcinoma occurs more frequently in Asian dermatomyositis patients.2 The risk of malignancy is highest in the period around the diagnosis of myositis, but this report demonstrates a continued risk for several years thereafter. With polymyositis, the increased risk seems to disappear after a few years. Perhaps the heightened vigilance for cancer upon diagnosis of polymyositis explains the modest increase in cancer found with this diagnosis. This study also debunks the notion that dermatomyositis-associated malignancy occurs only in the elderly.3 In this series, cancer occurred in dermatomyositis patients aged 45 and younger.
Dermatomyositis may be considered a paraneoplastic syndrome for a subset of patients. The symptoms of myositis frequently subside with effective cancer treatment, only to recur when disease relapses. There may be clinical and histological features of the myositis that are typical of cancer-associated disease. Patients with cancer-associated dermatomyositis are more likely to have normal creatinine kinase values and digital vasculitis, and less likely to have myositis associated antibodies than those without cancer.4
From a clinician’s perspective, the importance of this study lies in the implications for malignant disease workup in patients with dermatomyositis. In view of the increased risk of ovarian, lung, gastric, colorectal, pancreatic and breast cancer, and non-Hodgkin’s lymphoma, patients with dermatomyositis need a thorough evaluation and imaging studies at the time of diagnosis, and continued vigilance for the appearance of malignancy for many years thereafter. With the development of more effective therapies for these malignancies, this will become of greater importance.
1. Bohan A, Peter JB. N Engl J Med 1975;292:344-347.
2. Peng JC, et al. Arch Otolaryngol Head Neck Surg 1995;121:1298-1301.
3. Callen JP. Lancet 2000;355:53-57.
4. Fudman EJ, et al. Am J Med 1986;80:329-332.