Myositis and cancer have been linked since 1916, but few in-depth clinical research studies have been published. Myositis does not cause cancer, however, those with certain types of myositis have an increased risk and incidence of cancer, including polymyositis and a more notable increase for those with dermatomyositis.
A diagnosis of Cancer-Associated Myositis (CAM), a subtype of the idiopathic inflammatory myopathies (IIM), is made when cancer is diagnosed within one to two years of the onset of polymyositis or dermatomyositis. The incidence of cancer increases for those who test positive for the dermatomyositis-specific anti-TIF1γ autoantibody, as well as anti-NXP2. Age, sex, geographic location, and environment also play a role.
Cancer Risk and Risk Factors
The overall cancer rate varies between 9% and 32% for dermatomyositis (DM) patients, most often ovarian, lung, pancreatic, colorectal, and non-Hodgkin’s lymphoma. Most of these cancers occur after the onset of myositis symptoms, typically within the first 1 to 2 years, however colorectal and pancreatic cancer have been shown to occur later than 5 years.
The most common cancers seen in patients with DM include breast, colon, lung, ovarian, skin (melanoma), non-Hodgkin lymphoma (NHL), nasopharyngeal, and stomach.
The highest risk of developing cancer in patients with DM is within the first couple of years of myositis onset. Older patients and those with more severe findings on skin/muscle biopsy (cutaneous necrosis, capillary damage, and cutaneous leukocytoclastic vasculitis), prior history of cancer, and treatment resistance are at high risker of developing cancer within the DM population.
Approximately 15% of people with polymyositis (PM) are diagnosed with cancer, most often non-Hodgkin’s lymphoma, lung, and bladder. Some of these cancers (60-70%) are discovered after the onset of myositis. However, after one year post-diagnosis, the likelihood diminishes significantly, and by the 5th year post-diagnosis, the rate dropped to the cancer rate of the general population.
Risk factors for CAM include:
Previous history of cancer – If you have had cancer in the past, you are at higher risk for developing cancer with myositis.
Age at diagnosis – Those who are over 45 are at higher risk.
Family history of cancer – If your family has a history of cancer, you are at a higher risk of developing cancer.
Additional Cancer Risks
Not only do poly- and dermatomyositis come with a higher risk of cancer, but there are also other factors which increase the risk such as certain autoantibodies and medications used to treat myositis.
Myositis-specific and associated antibodies can provide insight into cancer risk. The presence of certain antibodies is linked with increased cancer risk, including those positive for TIF1-gamma (TIF1-γ) or NXP2. Testing positive for these, and others should alert your physician that you are at a higher risk of having cancer and to order the necessary cancer screenings.
Other autoantibodies that are currently known to be associated with increased cancer rates are P155/140 and Anti T1F1 (found in DM and JDM).
Patients positive for additional antibodies actually have a lower risk of developing malignancy (anti-SRP, antisynthetase, anti-Mi-2, anti-RNP, anti-Ku, and anti-PM-Scl).
Those with antisynthetase autoantibodies (most common is Anti-Jo-1 and others include Anti-PL-7, Anti-PL-12, Anti-EJ, Anti-OJ, Anti-KS, Anti-Ha, and Anti-Zo) are at a lower risk for developing cancer-associated myositis.
It is extremely rare for children and those with inclusion body myositis to develop cancer-associated myositis.
Immune Suppressing Medications (DMARDs)
In addition to cancer-associated myositis, there is thought to be a slight cancer connection with commonly used immunosuppressive medications such as Methotrexate, Imuran (azathioprine), and CellCept (mycophenolate).Myositis Treatments
NOTE: The statistics included are from research done in early 2016 and, depending on when you are reading this, may no longer be accurate. Be sure you also contact your physician should you have questions, concerns, or before deciding on a treatment due to risks shown here. This is for informational purposes only.
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More reading about Cancer and Myositis
Jeroen De Weirdt, Dissertation presented in the 2nd Master year in the programme of Master of Medicine in Medicine
“Simply Put” is a service of Myositis Support and Understanding, to provide overviews of Myositis-related medical and scientific information in understandable language.
MSU volunteers, who have no medical background, read and analyze often-complicated medical information and present it in more simplified terms so that readers have a starting point for further investigation and consultation with healthcare providers. The information provided is not meant to be medical advice of any type.