Neonatal phototherapy and future risk of childhood cancer.

We sought to determine if neonatal phototherapy is associated with a greater risk of childhood cancer. We conducted a retrospective cohort study of 786,998 infants born in hospitals of Quebec, Canada between 2006 and 2016, with 4,660,868 person-years of follow-up over an 11-year period. The exposures were neonatal phototherapy (32,314 or 4.1% of infants) and untreated jaundice (91,855 or 11.7% of infants). The outcome was hospitalization for solid or hematopoietic childhood tumours between 2 months and 11 years of age. We used Cox proportional hazards regression models to compute hazard ratios (HR) and 95% confidence intervals (CI) for the association of phototherapy with childhood cancer, adjusted for infant characteristics. The incidence of childhood cancer was higher for infants with phototherapy (25.1 per 100,000 person-years) and untreated jaundice (23.0 per 100,000) compared to unexposed infants (21.6 per 100,000). Phototherapy appeared to be associated with late onset solid tumours, including brain/central nervous system cancers. Between age 4 and 11 years, children who received neonatal phototherapy had more than 2 times the risk of any solid tumour compared to unexposed children (HR 2.26, 95% CI 1.34-3.81). Results were similar for phototherapy compared against untreated jaundice. A similar trend was however less apparent for hematopoietic cancer. We conclude that neonatal phototherapy may be associated with a slightly increased risk of solid tumours in childhood, but cannot rule out an effect of bilirubin. Minimizing unnecessary exposure to phototherapy through adherence to recommended thresholds for treatment is encouraged.