In a study reported in the Journal of Clinical Oncology, Pelland-Marcotte et al found that survivors of childhood leukemia remained at significantly increased risk of infection compared with matched controls during an extended period following completion of treatment.
Study Details
The population-based cohort study used administrative health data on 2,204 children diagnosed with leukemia between 1992 and 2015 in Ontario who were alive and relapse-free 30 days after completion of treatment (index date) and 11,020 controls matched for year of birth, sex, and rural status. The primary outcome was time to infection, identified using diagnostic codes from administrative databases. Subjects were censored at the earliest of death, first relapse, loss to follow-up, or end of study.
Infection Risk
The median follow-up time from index date was 7.2 years for leukemia survivors and 9.7 years for controls. A total of 104,410 infections were identified.
Risk of infection was significantly increased in leukemia survivors overall (unadjusted relative rate [RR] = 1.51, 95% confidence interval [CI] = 1.45–1.57), at < 1 year (RR = 1.77, 95% CI = 1.69–1.86), at 1 to 4.99 years (RR = 1.66, 95% CI = 1.62–1.71), and at ≥ 5 years (RR = 1.29, 95% CI = 1.22–1.36) from the index date. Among all survivors with initial treatment that did not include hematopoietic stem cell transplantation (HSCT), risk of infection remained elevated at ≥ 5 years (RR = 1.29, 95% CI = 1.23–1.35). Overall relative rates for infection were 1.50 (95% CI = 1.43–1.57) among survivors of acute lymphoblastic leukemia and 1.65 (95% CI = 1.50–1.82) among survivors of acute myeloid leukemia.
ELEVATED RISK
- Survivors of childhood leukemia remain at increased risk of infection over an extended period after completion of treatment.
- Risk remained elevated at ≥ 5 years among patients with initial treatment that did not include HSCT.
Risk of death due to infection was increased vs controls among all leukemia survivors (total deaths = 28; hazard ratio [HR] = 149.3, 95% CI = 20.4– 1,091.9) and among those without HSCT as part of initial treatment (total deaths = 18; HR = 92.7, 95% CI = 12.4–690.7).
The investigators concluded, “A significant association was found between a history of leukemia therapy and an increased risk of infections. Additional study is needed to establish which exposures in patients with leukemia lead to late infections.”
Marie-Claude Pelland-Marcotte, MD, of the Division of Haematology/Oncology, The Hospital for Sick Children, Toronto, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by the Institute for Clinical Evaluative Services, which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care. For full disclosures of the study authors, visit jco.ascopubs.org.
