Is there an association between Polymyositis or dermatomyositis and underlying cancer?
Associated cancers are present in about 10% to 20% of adult (not juvenile) patients with PM/DM and over 50% of patients who develop PM/DM after the age of 65 years. Most have DM (80%) with the remainder having PM (20%). These patients are referred to as having cancer-associated myositis. The malignancy is present at myositis onset or within the first year in 68%. If associated with a malignancy, the cancer almost always occurs within 3 years of myositis onset. Cancers reported in association with PM/DM are most often adenocarcinomas or hematologic and include, among others, breast, lung, pancreas, stomach, colon, ovary, hematopoietic cancer, and Hodgkin’s lymphoma. Taiwanese patients also have nasopharyngeal and cervical tumors. This association has long been controversial, but recent studies have shown a 3 to 6 times increased risk for malignancy in DM and 1.4 to 2 times increased risk for PM. Therefore, it is generally advised that patients with PM, and especially those with adult DM, be screened for underlying neoplastic disease. This screen should be age-appropriate and include a complete history and exam (including breast, pelvis, prostate), stool occult blood testing, chest x-ray, mammogram, colonoscopy (age, >50 years), and laboratory tests (complete blood count, complete metabolic panel, serum protein electrophoresis, and urinalysis). The MSA, anti-TIF-1γ (p155/140) and anti-NXP2 (MJ) antibodies, are reported to be associated with adult cancer-associated DM. Notably, the myositis-specific antisynthetase antibodies (e.g., anti-Jo-1) and anti-Mi-2 have a negative association with malignancy. Some clinicians also recommend an abdominal/pelvic computed tomography scan owing to the high incidence of lymphoma and ovarian cancer, whereas others feel that a positron emission tomography scan is a cost-effective screen, especially in patients with MSAs associated with cancer. Although controversial, some physicians advocate testing for tumor markers associated with common cancers (CEA, CA 125, CA 19-9, CA15-3). If the initial cancer screen is negative, the physician should be alert for future development of cancer over the next 3 years.
Pearl: Ulcerative skin lesions in an adult DM patient are highly associated with an underlying malignancy.