No Increased Risk of RA in Women With History of Breast Cancer Taking Anti-Hormonal Therapy

May 14, 2020

Women with breast cancer treated with tamoxifen or aromatase inhibitors did not have an increased risk of rheumatoid arthritis (RA) compared with women with breast cancer who did not take either therapy, according to a study published in the Annals of the Rheumatic Diseases.

Using nationwide Swedish registers, Hjalmar Wadström, Karolinska Institutet, Stockholm, Sweden and colleagues identified 15,921 women who were diagnosed with RA between 2006 and 2016. Each patient with RA was matched on age, sex and place of residence to 5 randomly selected subjects from the general population. Through register linkages, the researchers collected information on breast cancer, breast cancer risk factors (reproductive history and hormone replacement therapy), and socio-economic factors.

The relative risk of breast cancer after RA was assessed using Cox regression, and the relative risk of RA in women with a history of breast cancer was assessed using conditional logistic regression.

The risk of incident breast cancer in women with RA was reduced and the association was not attenuated by adjustment for breast cancer risk factors (hazard ratio = 0.80; 95% confidence interval [CI], 0.68-0.93). The risk of RA in women with a history of breast cancer was similarly reduced (odds ratio [OR] = 0.87; 95% CI, 0.79-0.95). Women with breast cancer treated with tamoxifen (OR = 0.86; 95% CI, 0.62-1.20) or aromatase inhibitors (OR = 0.97; 95% CI, 0.69-1.37) did not have an increased risk of RA compared with women with breast cancer treated differently.

“Our investigations show that although the risk of breast cancer in women with rheumatoid arthritis is reduced, this correlation cannot be easily explained by conventional risk factors for breast cancer,” said Wadström. “Even the use of anti-hormonal therapy for breast cancer does not seem to increase the risk of RA.”

“We now know that breast cancer is less common in patients with RA and that tamoxifen and aromatase inhibitors appear to be safe in terms of the risk of future RA at least in the observed first few years,” said John Isaacs, MD, Newcastle University, Newcastle, United Kingdom. “This is important information for patient counselling. Nevertheless, all patients with a symptomatic rheumatoid disease should regularly attend tumour screening with a frequency appropriate to their age.”

References: https://ard.bmj.com/content/79/5/581

SOURCE: European League Against Rheumatism