People with systemic lupus erythematosus are 1.15 times as likely to develop cancer as the general population and more than 2.5 times as likely to develop hematologic malignancies, such as lymphoma and leukemia, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in Atlanta.
Systemic lupus erythematosus, also called SLE or lupus, is a chronic inflammatory disease that can affect the skin, joints, kidneys, lungs, nervous system, and/or other organs of the body. The most common symptoms include skin rashes and arthritis, often accompanied by fatigue and fever. Lupus occurs mostly in women, typically developing in individuals in their twenties and thirties - prime child-bearing age.
Some studies have shown a link between lupus and cancer risk, and researchers recently aimed to make more precise estimations of this risk. They observed 13,492 people with lupus from 24 medical centers for an average of nine years, for a total of 118,359 patient-years (number of patients multiplied by number of years of observation), and compared these participants to people without lupus.
During the course of this study, 632 cases of cancer were noted, and the data concerning hematological cancers—cancers that affect the bone, blood and lymph nodes—was the most striking: researchers found that people with lupus were 3.2 times more likely to develop lymphomas than the general population and 3.4 times more likely to develop non-Hodgkin's lymphoma, specifically. They also found that people with lupus were 1.7 times greater risk of developing leukemia.
"These results more precisely define cancer risk in SLE [than previous studies], highlighting a higher risk of hematological malignancies - both lymphoma and leukemia," says Sasha R. Bernatsky, MD, assistant professor in the Department of Medicine, Divisions of Rheumatology and Clinical Epidemiology, at McGill University, a medical scientist at the Research Institute of the McGill University Health Centre, and co-principle investigator in the ongoing study along with Ann E. Clarke, MD, and Rosalind Ramsey-Goldman, MD, Dr.PH. "However, the news may not be all that bad, considering that hematological cancers remain a rare event - one in every 1,250 patient-years of follow-up for these patients. Just what is driving the risk of cancer in SLE is still unknown, but we currently suspect that disease activity plays a role, although drug exposures have not been ruled out."
Study participants also demonstrated an increased likelihood of developing lung cancer (1.2 times as likely as the general population), cervical cancer (1.6 times more likely), vulvo-vaginal cancers (2.8 times more likely), and liver cancer (2. 2 times more likely). The study also shows that people with lupus who are younger than 40 have a particularly high risk, as they are 1.7 times more likely to develop cancer than the general population.
On the other hand, participants did display a significantly decreased risk of developing hormone-sensitive cancers, including breast cancer (0.7 times as likely as the general population), endometrial cancer (0.49 times the likelihood), and ovarian cancer (0.56 times the likelihood).
"The lower risk of several hormone-sensitive cancers may invoke the possibility of alterations in the metabolism from estrogen and/or other hormones," Dr. Bernatsky explains. "But, because female SLE patients may be at higher risk for cancers and pre-cancerous changes of the uterine cervix, they should try to undergo pap testing regularly once they become sexually active, especially if they take immunosuppressive drugs."
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