Much of the increase in mortality in people with rheumatoid arthritis who are also diagnosed with cancer may be due to the inflammatory effects of the arthritis or its treatment, and not the cancer.
Rheumatoid arthritis is a chronic inflammatory disease that affects a person’s joints, causing pain and disability. It can affect both men and women of all ages. The inflammation can also affect people’s internal organs. Patients with rheumatoid arthritis have a higher risk of developing cancer and a shorter lifespan compared to healthy people of the same age. Decreased survival in people with rheumatoid arthritis is still a problem despite the availability of new treatments for the disease.
WHAT DID THE AUTHORS HOPE TO FIND?
The authors hoped to find out whether the underlying inflammation involved in rheumatoid arthritis contributes to the survival of people suffering from rheumatoid arthritis and cancer.
WHO WAS STUDIED?
The study looked at 34,930 people with rheumatoid arthritis, and compared their records to those of 169,740 people in the general population. Everyone was between 40 and 80 years of age, had at least two visits coded for RA in outpatient care with at least one with an RA specialist between 2001 and 2009.
HOW WAS THE STUDY CONDUCTED?
This was a population-based cohort study using a large register linkage in Sweden including the National Patient Register and the Cancer Register. The study was observational; therefore, no medicine or intervention was specifically under investigation. The authors used these data to see who developed cancer and whether they died. Investigators included all malignancies, and six specific ones were considered separately: lung, colorectal, malignant melanoma, breast (in women), prostate (in men) and lymphoproliferative malignancies. The study also collected information on diseases that people had in addition to rheumatoid arthritis, such as chronic obstructive pulmonary disease, ischaemic heart disease, diabetes and cerebrovascular disease. In addition, the study calculated the effect of rheumatoid arthritis on mortality by cancer stage and time since cancer diagnosis.
WHAT WERE THE MAIN FINDINGS OF THE STUDY?
Overall, 7% of people in the study with rheumatoid arthritis developed cancer compared to 6% of people who did not have rheumatoid arthritis. But the main findings of the study were that people with rheumatoid arthritis but no cancer had twice the mortality rate of people in the normal population. This was similar for people with cancer at an early stage – people with rheumatoid arthritis and stage 1 or 2 cancer were more likely to die than people with the same cancers but no rheumatoid arthritis. This may be due to increased mortality from cardiovascular disease and other causes related to the underlying rheumatoid arthritis. There was less of a difference in the death rate for cancers diagnosed at later stages, which may be due to the underlying severity and fatality of these cancers.
ARE THESE FINDINGS NEW?
These findings are relatively new. Most studies looking at cancer in people with rheumatoid arthritis have focused on how often people get cancer, but not how long they survive for. A few studies found similar results of reduced survival following cancer among people with rheumatoid arthritis compared to those without, however not always accounting for stage at cancer diagnosis.
HOW RELIABLE ARE THE FINDINGS?
There are some limitations which may affect the reliability of the findings. For example, the authors did not have very much information on how people were treated for their cancer, and if they went on to have relapses. The results are therefore limited to looking only at the first cancer diagnosis.
WHAT DO THE AUTHORS PLAN ON DOING WITH THIS INFORMATION?
The authors plan to do more studies to look in detail at the role of various factors on the occurrence and outcome of cancer in people with rheumatoid arthritis.
WHAT DOES THIS MEAN FOR ME?
If you have rheumatoid arthritis, you may be more likely to develop some cancers, and you may have a shorter lifespan than other people your age. However, if you are diagnosed with advanced-stage cancer, having rheumatoid arthritis as well does not affect your long-term outlook. Your doctor may perform checks for common kinds of cancer, and you should make sure that you attend all screening appointments you are called for. If you are concerned about cancer, you should talk to your doctor.
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Date prepared: May 2016
Summary based on research article published on: 6 May 2015
From: Simard, JF. et al. What is the impact of chronic systemic inflammation such as rheumatoid arthritis on mortality following cancer? Ann Rheum Dis 2016;75:862–66. doi:10.1136/annrheumdis-2014-207155
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Smolen J, et al. Treating rheumatoid arthritis to target: 2014 update of the recommendations of an international task force. Ann Rheum Dis 2016;75:3–15