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. What's new? While phototherapy is widely used to treat neonatal jaundice, it can induce oxidative stress and DNA damage. Whether these factors raise the risk for subsequent development of childhood cancer remains uncertain. Here, associations between phototherapy and childhood cancer risk were investigated among infants born between 2006 and 2016 in Quebec, Canada. Childhood cancer incidence was found to be elevated among phototherapy‐treated infants and infants with untreated jaundice. Phototherapy appeared to be associated in particular with solid tumors that developed later, between ages 4 and 11. Closer study is needed to disentangle the potentially carcinogenic effects of phototherapy from hyperbilirubinemia.