Patients with pediatric-onset systemic lupus erythematosus (SLE) are at an increased risk for cancer, especially hematologic cancers, new data suggest.
“In the past decade, there have been several large studies elucidating cancer risk in adults with [SLE]. However, relatively little is known about cancer risk in childhood-onset SLE,” Sasha Bernatsky, MD, PHD, of McGill University in Montreal, and colleagues reported in Arthritis Research & Therapy.
In one study of adults with SLE, cancer incidence was four times the expected rate. However, little is known about SLE and cancer risk in kids.
So Bernatsky and colleagues examined SLE registries at 10 pediatric rheumatology centers that included data from 1974 to 2009. A total of 1,020 patients with a mean age of 12.6 years at cohort entry were observed for a mean 7.8 patient-years. Eighty-two percent of patients were female, and the majority was white.
Fourteen cases of cancer occurred during a period in which only three cases were expected, for a standardized incidence ratio (SIR) of 4.7 (95% CI, 2.6-7.8).
Of the three cases, there were two cases of non-Hodgkin lymphoma and one case of leukemia, for a SIR of 5.2 (95% CI, 1.1-15.2). One male and one female received lymphoma diagnoses at ages 16 and 28 years, respectively. The patient with leukemia received the diagnosis at age 7 years.
Both the patient with leukemia and the one with non-Hodgkin lymphoma were diagnosed within one year of receiving an SLE diagnosis, according to the researchers. Nonhematologic cancers included four that were unspecified, three head and neck malignancies, and one each for thyroid, brain, breast and bladder.
Cancer diagnosis occurred after a mean SLE duration of 12.3 years, with data indicating a trend toward higher cancer occurrence 10 to 19 years after SLE diagnosis.
Confidence intervals for SIRs appeared to be wider across sex strata as well as for those aged 0 to 19 years and those aged older than 20 years for hematologic cancer, the researchers reported.
“This study represents the most up-to-date results from our multicenter initiative to clarify baseline cancer risk in pediatric-onset SLE,” the researchers wrote. “There is a possible increased risk in overall cancer, which may be driven by hematologic cancer risk. Further work in progress will compare risk across geography, race/ethnicity, and disease subset.”