Phototherapy is the go-to therapy for treating significant hyperbilirubinemia and has been for decades. While we certainly are aware of the potential common complications of phototherapy (e.g. needing to protect the eyes from the ultraviolent light being used), recently two studies were submitted for peer-review that raised a less-considered possible complication—an increased risk of cancer in young children among babies who underwent this treatment. After substantive peer-review, we are publishing both studies this week along with an important commentary that frames the results with the proper perspective.
The first study by Wickremasinghe et al. (peds.2015-1353) uses a dataset from the California Office of Statewide Health Planning and Development that provides birth, death, and hospital discharge information on more than 5 million infants born at 35 weeks gestation or higher from 1998 to 2007. ICD-9 codes were obtained from this database for phototherapy usage at less than 15 days and subsequent discharge diagnoses of cancer at age 2 months to one year of age. Confounding variables were adjusted using logistic regression models.
The results of this study at face value suggest an increased association between phototherapy and overall cancer (as well as with more specifically myeloid leukemia and kidney cancer) with a relative risk of 1.6 but an absolute increased risk of 9.4 cases per 100,000 infants given phototherapy—a small increase.
The second study by Newman et al. (peds.2015-1354) was a retrospective cohort study involving close to 500,000 children born ag 35 weeks gestation or higher from 1995-2011 in Kaiser Permanente Northern California hospitals followed at least two months postnatally. Kaiser’s electronic records noted home or hospital phototherapy and cancer incidence in these patients. Again adjustments were made to control for possible confounding and unequal follow-up periods. In this study, phototherapy was associated with an increased risk of leukemia (relative risk 2.1) and liver cancer (relative risk 5.2) initially but after adjustment for confounders, these associations were no longer statistically significant except for the risk of leukemia among infants with Down syndrome.
So what can we make of these two studies? Should we stop using phototherapy? That is not the intent of either of these studies—but simply to note that perhaps we should choose even more wisely who really needs phototherapy and who does not. There are certainly limitations one must consider with both studies that could have influenced the findings the authors have published, and to better understand what can be learned, please read the commentary by Dr. Lindsay Frazier-Seabrook, a specialist in cancer epidemiology, and colleagues that is also being released online today (peds.2016-0983).
This commentary does an excellent job of putting the findings into perspective—not denying there may be an increased risk of childhood cancers as identified in these two studies, but also making sure we understand the small absolute risk of this happening, and the problems that both datasets present when used to find associations like the ones in these two articles.
It is likely both studies will garner some national attention—but both should be viewed in the light of the accompanying commentary and not just the light emanating from the phototherapy being used. We welcome your thoughts on the two studies and commentary by responding to this blog, writing a comment on the online site for these studies, or sharing your thoughts with a posting on our Facebook or Twitter links.