Myositis and cancer have been linked since 1916, but few in-depth clinical research studies have been published. The findings of those studies, however, show an increased incidence of cancer in patients with Polymyositis and a significant increase for those with Dermatomyositis.
Whether cancer can cause Myositis is also minimally researched, but it is recognized that cancers can occur within 2 years prior to the onset of Myositis symptoms.
Cancers are known to occur in approximately 32% of Dermatomyositis patients, most often ovarian, lung, pancreatic, colorectal, and non-Hodgkin’s lymphoma. Most of these cancers (58%) occur after the onset of Myositis symptoms, typically within the first 2 to 5 years, however colorectal and pancreatic cancer have been known to occur later than 5 years.
Approximately 15% of people with Polymyositis are diagnosed with cancer, most often non-Hodgkin’s lymphoma, lung, and bladder. Most 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 normal population.
Juvenile Myositis and Inclusion Body Myositis do not appear to carry a higher rate of cancer than the average population.
Additional Cancer Risks
Not only do Poly- and Dermatomyositis come with a higher risk for cancer, there are other factors which increase the risk such as certain autoantibodies and the medications taken to treat Myositis.
Some Dermatomyositis patients test positive to certain autoantibodies for which there is a higher likelihood of cancers. The autoantibodies which are currently known to be associated with increased cancer rates are P155/140 and Anti T1F1.
It is also thought that the anti-CADM-140 antibody (which appears in patients with Amyopathic Dermatomyositis (ADM)) may show a higher increase in internal cancers than the average population, but there are few statistics at this time.
A corticosteroid medication such as Prednisone/Prednisolone is most often the first line of treatment for Polymyositis and Dermatomyositis. It is highly effective in quickly treating muscle inflammation, but there is an increased risk of non-Hodgkin’s lymphoma and non-melanoma type skin cancers. The cancer risks increase with the length of time and dosage of corticosteroids.
Immune Suppressing Medications (DMARDs)
In addition to the Myositis-cancer connection, there is a cancer connection with commonly- used immunosuppressive medications such as Methotrexate, Imuran (Azathioprine), and CellCept (Mycophenolate), all of which show an increased incidence of non-Hodgkin’s lymphoma and lung cancers.
Methotrexate is also associated with melanoma, while non-melanoma skin cancers are seen more with Imuran and CellCept.
Suggested Cancer Screenings
In addition to the Myositis Specific Antibodies (MSA) panel (which should be conducted as part of the Myositis diagnosis and can show if cancer-related antibodies exist) regular Complete Blood Count (CBC), Comprehensive Metabolic Panel (CMP), and urinalysis (UA) should be conducted.
In addition to tests which may be appropriate based on a patient’s age, the following cancer screening tests are suggested:
NOTE: The statistics included are as of 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.
“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.