Rheumatoid arthritis is an autoimmune disorder that affects mainly the joints, but also can affect the skin, eyes, lungs, heart, and blood vessels. It happens when the body’s immune system attacks the lining of the joints causing painful swelling.
Inflammatory bowel disease is another autoimmune disorder that involves chronic inflammation of all or part of the digestive tract, including the colon, large intestine, and rectum.
Both diseases are treated with medicines that suppress the immune system. So researchers wondered if women who took immunosuppressant medicines for rheumatoid arthritis or inflammatory bowel disease had a higher risk of breast cancer recurrence than women who didn’t take these medicines.
A study offers good news: Women who had been treated for breast cancer who then took methotrexate (one brand name is Rheumatrex) or anti-tumor necrosis factor medicines for rheumatoid arthritis or inflammatory bowel disease didn’t seem to have a higher risk of recurrence than women who didn’t take these medicines.
The study was published online on May 9, 2016 by the journal Arthritis & Rheumatology. Read the abstract of “Association between breast cancer recurrence with immunosuppression in rheumatoid arthritis and inflammatory bowel disease: A cohort study.”
Anti-tumor necrosis factor medicines include Remicade (chemical name: infliximab), Humira (chemical name: adalimumab), and Enbrel (chemical name: etanercept).
The study included 2,684 women who had been treated for breast cancer between 2000 and 2012 and then were diagnosed with either rheumatoid arthritis or inflammatory bowel disease. All the women had Medicare as their insurance; 85% of the women were age 65 or older and 87% of the women were white.
The researchers reviewed the women’s medical records and put them into three matched groups based on the type of breast cancer surgery the women had, the type of treatments given after surgery (if any), as well as the immunosuppressant medicine the women were taking:
- methotrexate group: 892 women being treated with methotrexate and 892 not being treated with the medicine
- anti-tumor necrosis factor group: 291 women being treated with an anti-tumor necrosis factor medicine and 1,164 women not being treated with that type of medicine
- thiopurine group: 52 women being treated with a thiopurine and 208 women not being treated with that type of medicine
Thiopurine medicines are another type of immunosuppressant commonly used to treat inflammatory bowel disease. Thiopurines include Imuran (chemical name: azathioprine) and Purinethol (chemical name: mercaptopurine).
Then the researchers looked to see how many women had a breast cancer recurrence a year or more after their initial diagnosis.
Overall, 107 women had a breast cancer recurrence.
There was no difference in breast cancer recurrence risk for women:
- who were and were not treated with methotrexate
- who were and were not treated with an anti-tumor necrosis factor medicine
Women who were treated with a thiopurine had a risk of recurrence that was twice as high as women who weren’t treated with a thiopurine. Still, this difference wasn’t statistically significant, which means that it could have been due to chance and not just because of the difference in medicine.
Because of the smaller number of women in the thiopurine group, the researchers said that more research is needed to better understand if women treated with thiopurines actually have a higher risk of breast cancer recurrence.
For women diagnosed with rheumatoid arthritis or inflammatory bowel disease who have been treated for breast cancer in the past, this study offers some encouraging news.
"We found it interesting that anti-[tumor necrosis factor] users were not at higher risk of recurrence compared with nonusers, particularly since this finding does not support current clinical practice, in which many physicians avoid anti-TNF therapy in patients with recently treated cancer," Ronac Mamtani, M.D., of the University of Pennsylvania Abramson Cancer Center and first author of the paper, said in an interview. "The results of our study provide the strongest evidence to date to support [the] 2015 American College of Rheumatology guidelines recommending that [rheumatoid arthritis] patients with previously treated and presumed cured solid malignancies should not be treated differently than [rheumatoid arthritis] patients without these conditions."
It’s important to know that the study did have some limitations:
- The researchers didn’t know how severe the women’s rheumatoid arthritis or inflammatory bowel disease was. If the disease were more severe, it’s possible that the women’s immune systems could be more suppressed, which could increase recurrence risk.
- The results of the study can’t be applied to women who are actively being treated for breast cancer. This study only looked at women who were done with breast cancer treatment.
Still, if you have been treated for breast cancer in the past and are now being treated for rheumatoid arthritis or inflammatory bowel disease, the results of this study are very reassuring.
For more information, visit the Breastcancer.org Understanding Your Immune System pages.