Background/Purpose: Compared to adults with SLE, relatively little is known about cancer risk in pediatric-onset SLE. We assessed cancer incidence in a multi-centre pediatric-onset SLE cohort, compared to general population cancer rates.

Methods: We ascertained cancers within SLE clinic registries at 10 pediatric centers, located in Birmingham AL; Cincinnati OH, Durham NC; Hackensack NJ; Oklahoma OK; San Francisco CA; Montreal QC; Toronto ON; Saskatoon SK; and Winnipeg MB. Subjects were linked to state or provincial cancer registries for the observational interval, spanning 1974–2009. In-situ cancers were excluded. Follow-up was calculated from the date first seen at the clinic, and the first of 3 possible events: death, cancer, or end of study interval (Dec. 2009). We pooled observed cancers and person-years of observation. The cancers expected to occur were calculated by multiplying the person-years in the cohort by the geographically matched age, sex, and calendar year-specific cancer rates. The ratio of observed to expected cancers represents the SIR, or relative cancer risk in pediatric SLE, versus the general population. We provided estimates for total cancer and for hematological cancers, and also results stratified on sex, age group, and SLE duration.

 Results: There were 999 patients aged <18 at cohort entry. Most (82%) were female; mean age at cohort entry was 12.9 years (SD=3.6).The majority were Caucasian. Subjects were observed for a total of 7,986 patient-years (average 8.0 years). Within this interval, only 3.0 invasive cancers were expected, however, 14 invasive cancers occurred, for an SIR of 4.7, 95% confidence interval, CI 2.6, 7.8. Three hematologic cancers were found (2 non-Hodgkin’s lymphoma, 1 leukemia), for an SIR of 5.2 (95% CI 1.1, 15.2). The non-hematologic cancers included one cancer each of bladder, brain, breast, and thyroid, 3 head and neck cancers, and 4 unspecified cancers. At time of cancer diagnosis, mean SLE duration was 12.3 years (range 0.1, 25.2 years).  Excluding cancers that occurred within the first year of cohort entry, the over-all cancer SIR was 3.0 (95% CI 2.3, 7.8). The SIRs stratified by age group and sex, were similar across strata (though more precise for females than males, due to relatively small numbers of males). Though not definitive, there was a trend for heightened relative risk in the period 10-19 years after SLE diagnosis. However, in absolute terms, this stratum experienced only 8 cancers.

Conclusion: These up-dated results suggest an increased cancer risk in pediatric onset SLE versus the general population. However, in absolute terms, this still translates into few events, which is somewhat re-assuring. A limitation is that some patients may have developed a cancer after relocating to another state or province, thus under-representing the true cancer incidence. Of note, risk may be highest in the period 10-19 years after SLE diagnosis, at a time when patients will have transferred to an adult provider. Further work will assess other potential factors of interest, such as race/ethnicity and calendar effects. Our work highlights the importance of continuity as adolescents transition to adult care, and a need for collaborations to allow longitudinal assessment of long-term risks.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/cancer-in-pediatric-onset-systemic-lupus-what-is-the-role-of-disease-duration-and-other-factors-on-risk/