Immunosuppressive drugs do not increase risk of cancer in lupus patients

People who take immunosuppressive drugs to treat lupus do not necessarily increase their cancer risk according to new research led by scientists at the Research Institute of the McGill University Health Centre (RI-MUHC). This landmark study, which was published in Annals of the Rheumatic Diseases this month, addresses long-standing fears of a link between lupus medication and cancer.

Systemic lupus erythematosus (SLE), commonly known as lupus, is an autoimmune disease in which the body's immune system attacks healthy tissue such as the skin, joints, kidneys and the brain, leading to inflammation and lesions. The disease affects about 1 in 2000 Canadians, particularly women.

Previous research has suggested that lupus patients have an increased risk of developing cancer, particularly lymphoma. Lymphoma is a type of blood cancer that occurs when cells called lymphocytes, which usually help protect the body from infection and disease, begin growing and multiplying uncontrollably leading to tumor growth.

"Treatment for Lupus consists largely of immunosuppressive medications, which lower the body's immune response," explains Dr. Sasha Bernatsky, first and corresponding author of the study, who is a researcher within the Divisions of Clinical Epidemiology and Rheumatology at the RI-MUHC and at McGill University.

According to Dr. Ann E. Clarke, director of the MUHC lupus clinic and study co-lead, the fear of developing cancer among Lupus patients has been so great that some were reluctant to take their medication and others stopped altogether. The international study involved 75 lupus patients with lymphoma from different centres around the world and nearly 5,000 cancer-free lupus patients as a control.

Researchers studied most of the drugs commonly used to treat SLE including cyclophosphamide, a drug reserved for severe lupus cases and other chronic inflammatory rheumatic diseases.

The results showed that the risk for lymphoma in lupus patients exposed to cyclophosphamide was less than 0.1% per year. In addition, no clear association was observed between lupus disease activity and lymphoma risk.

"People have been wondering for a long time whether the medications were to blame and the results are reassuring, suggesting that most lymphoma cases in SLE are not triggered by drug exposures," says Dr. Bernatsky.

"This is very good news that cancer risk associated with lupus medication is relatively low," said Louise Bergeron, who has been living with lupus for 12 years.

"It reassures me, especially if I need to take more effective immunosuppressive treatments in the coming years."

Future research will focus on the genetic profiles of lupus patients and what impact that can have on the interaction between medication exposure and lymphoma risk in lupus.