Nov. 9, 2010 (Atlanta) -- People with systemic lupus are 15% times more likely to develop cancer compared with the general population, suggest findings of a study involving nearly 13,500 people with systemic lupus.
The higher malignancy rate among people with systemic lupus is driven mainly by an increased risk of cancers of the white blood cells, particularly a threefold increased risk of lymphoma, says researcher Sasha R. Bernatsky, MD, assistant professor in the divisions of rheumatology and clinical epidemiology at McGill University in Montreal.
Because lymphoma is a relatively rare cancer, however, the absolute risk of any person with lupus developing it is still quite low, she tells WebMD.
"If you follow 200 patients with lupus for a year, maybe you would see one lymphoma," Bernatsky says. "Although important ... we don't want to be overstating the finding."
Not all the news is bad. In what she calls one of the most surprising findings, she says that women with systemic lupus were less likely to develop estrogen-sensitive cancers, specifically those of the breast (30% decreased risk), endometrium (51% decreased risk), and ovary (44% decreased risk).
"This raises the possibility that something about how women with lupus metabolize estrogen may be involved," Bernatsky says.
She presented the findings here at the American College of Rheumatology Annual Scientific Meeting.
More Cancer Cases Than Expected Among People With Systemic Lupus
Systemic lupus is a chronic inflammatory disease that can affect the skin, joints, nervous system, kidneys, lungs, and other organs in the body. The most common symptoms include skin rashes and arthritis, often accompanied by fatigue and fever. Lupus occurs mostly in women and typically develops in people in their 20s and 30s.
The same research group previously demonstrated an association between systemic lupus and cancer in a smaller study. The current study was designed to more precisely estimate cancer rates among people with lupus, compared with the general population.
The study involved 13,492 people with lupus from 24 medical centers followed for an average of nine years. Using regional tumor registries, the researchers pinpointed people with systemic lupus and compared their cancer rates to what was expected in the general population.
Over the course of the study, 632 cases of cancer were noted among people with systemic lupus, "more than what we expected," Bernatsky says.