Patients with arthritis, a disease characterized by inflammation in joints, experience significant joint stiffness and pain. One of the most common subtypes of arthritis is rheumatoid arthritis, which is a type of inflammatory arthritis that affects to up to one percent of the world’s population.
Patients with rheumatoid arthritis are at a higher risk of several different types of complications. In particular, patients are at a higher of developing certain types of cancers. While researchers are not entirely sure why, they speculate that it is likely due to these two reasons:
- Inflammation. Rheumatoid arthritis is characterized by high levels of inflammation, which can lead to the development of different types of cancers.
- Medicines. The drugs that are used to treat rheumatoid arthritis can increase the risk of certain cancers as they tend to be immunosuppressive. Normally, the immune system plays a major role in finding and eliminating cancer cells. However, suppressing the immune system using an immunosuppressant dampens the body's protective mechanism.
However, it is important to keep in mind that while the relative risk of developing cancer is high, the actual risk is very low. In fact, rheumatoid arthritis has also been linked to a lower risk of some types of cancers.
The following types of cancer seem more likely in patients with rheumatoid arthritis compared to the general population:
- Non-Hodgkin’s lymphoma and Hodgkin’s disease. Among all cancers, rheumatoid arthritis increases the risk of non-Hodgkin’s lymphoma and Hodgkin’s disease the most. These are two types of cancer that develop in the cells of the immune system. One study found that rheumatoid arthritis patients have a two-fold higher risk of developing non-Hodgkin's lymphoma and a three-fold higher risk of developing Hodgkin's disease compared to patients without rheumatoid arthritis. Furthermore, another study indicated that patients with the most severe rheumatoid arthritis were at the greatest risk of developing lymphoma. This might be the result of chronic stimulation of the immune system, which occurs in uncontrolled rheumatoid arthritis.
- Lung cancer. Rheumatoid arthritis has been linked to a higher relative risk of developing lung cancer. This could be the result of smoking, as smoking also increases someone's odds of developing rheumatoid arthritis in the first place. However, studies have also shown that patients with rheumatoid arthritis who don’t smoke still have a slightly higher risk of developing lung cancer compared to the general population. If a patient doesn’t smoke, their risk of lung cancer is actually very small. However, these patients still might experience inflammation and scarring of the lungs. Therefore, the most beneficial thing you can do to prevent lung cancer is smoking. Furthermore, if you are a rheumatoid arthritis patient with lung disease, then avoid taking methotrexate or leflunomide as that can worsen lung damage.
- Skin cancer. Patients with rheumatoid arthritis who take a type of medication known as TNF inhibitors are more likely to develop melanoma as these drugs suppress the immune system. In fact, one study found that using TNF inhibitors eads to a two-fold greater risk of developing melanoma compared to rheumatoid arthritis patients who do not. However, again, the actual risk is very low. Furthermore, another study found that patients that take TNF inhibitors have a 45 percent greater risk of developing non-melanoma skin cancer.
- Lymphoma associated with TNF inhibitors. While extremely rare, there have been two documented cases of patients with rheumatoid arthritis developing a rare type of non-Hodgkin's lymphoma called hepatosplenic T-cell lymphoma while taking TNF-inhibitors. The FDA has reported 40 other cases of this type of cancer in patients with other diseases who were also being treated with TNF inhibitors.
- Leukemia. The link between leukemia and rheumatoid arthritis is a little controversial. One study found that men with rheumatoid arthritis, but not women, had a higher rate of developing leukemia. Studies have shown that some medicines used in treatment of rheumatoid arthritis, including Cytoxan (cyclophosphamide) and Azasan (azathioprine), can increase the risk of leukemia.
Interestingly, there are several types of cancers that are actually less prevalent in patients with rheumatoid arthritis. These include:
- Breast cancer. One study found that patients with rheumatoid arthritis have a 16 percent lower chance of developing breast cancer compared to patients without rheumatoid arthritis. While scientists are unsure why, they believe this could be due the fact that many rheumatoid arthritis patients frequently use nonsteroidal anti-inflammatory drugs (NSAIDs), which lower inflammation.
- Colorectal cancer. Similar to breast cancer, patients with rheumatoid arthritis have a 23 percent lower risk of developing colorectal cancer. Again, this is likely due to administration of NSAIDs to curb inflammation.
- Prostate cancer. Studies have found that long-term use of NSAIDs can reduce the risk of developing prostate cancer in patients with rheumatoid arthritis. Furthermore, a study found that men with rheumatoid arthritis and prostate cancer had a 12 percent reduced risk of death compared to those that just had prostate cancer. In fact, men that have been hospitalized for treatment of rheumatoid arthritis had the lowest mortality rates (likely because they were taking NSAIDs).