Risk of Pediatric Cancer and Breastfeeding
by Anne Eglash MD, IBCLC, FABM
There has been evidence in the last few decades that breastfed children have a lower risk of developing certain types of pediatric cancers. This should not seem far-fetched, since there are several components in breastmilk that help to reduce the risk of cancer formation, such as stem cells and human alpha-lactalbumin (HAMLET).
According to the United States National Cancer Institute, cancer is the leading cause of death by disease past infancy among children in the USA. In 2021, it is estimated that 15,590 children between the ages of 0 and 19 will be diagnosed with cancer and 1780 will die in the USA.
The authors of this week’s study sought to evaluate all existing studies on pediatric cancer and breastfeeding, not only to determine the relationship between a history of breastfeeding and the risk of pediatric cancers, but also to study whether a specific duration of breastfeeding is most protective. Forty-five articles involving 475,579 individuals met their criteria for a meta-analysis. Thirty-three studies evaluated the association between breastfeeding and leukemia, 11 studies on lymphoma, 7 studies on brain tumors, 4 studies on neuroblastoma, 4 studies on sarcoma, 3 studies on nephroblastoma, 2 studies on retinoblastoma, and 2 studies on germ cell tumors.
They found a lower risk of childhood leukemia and neuroblastoma among children who were breastfed. Breastfeeding for 9.6 months had the most protective effect from childhood leukemia.
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The aim of this study was to quantitatively summarize the available evidence on the association of breastfeeding with the risk of childhood cancer.
A literature search of PubMed and Embase databases was performed to identify eligible observational studies published from inception to July 17, 2020. The categorical and dose-response meta-analysis was conducted by pooling relative risk (RR) or odds ratio (OR) estimates with 95% confidence intervals (CIs). Potential sources of heterogeneity were detected by meta-regression and stratification analysis. Sensitivity analysis and publication bias test were also carried out.
Forty-five articles involving 475,579 individuals were included in the meta-analysis. Among the thirty-three studies on the association between breastfeeding and risk of childhood leukemia, the pooled risk estimates were 0.77 (95% CI, 0.65–0.91) and 0.77 (95% CI 0.63–0.94) for ever versus non/occasional breastfeeding and longest versus shortest breastfeeding duration group, respectively. There was clear indication for non-linear dose-response relationship between breastfeeding duration and the risk of childhood leukemia (P non-linear < 0.001). The most protective effect (OR, 0.66, 95% CI 0.62–0.70) was observed at a breastfeeding duration of 9.6 months. Four studies examined, the association between breastfeeding and risk of childhood neuroblastoma, and significant inverse associations were consistently observed in both the comparisons of ever breastfeeding versus non/occasional breastfeeding (OR = 0.59, 95% CI 0.44–0.81) and longest versus shortest breastfeeding (OR = 0.61, 95% CI 0.44–0.83). However, no associations of breastfeeding with risk of other cancers were found.
Our study supports a protective role of breastfeeding on the risk of childhood leukemia, also suggesting a non-linear dose-response relationship. Further studies are warranted to confirm the association between breastfeeding and risk of childhood neuroblastoma.
The bulk of the studies were done on childhood leukemia, since acute lymphoblastic leukemia (ALL) is the most common childhood cancer. The researchers did not find a continual decline in the risk of childhood leukemia with extended breastfeeding. In other words, breastfeeding for more than 15 months did not demonstrate an even greater decrease in the risk of leukemia.
The National Cancer Institute’s webpage on pediatric cancers mentions that breastfeeding is one factor that reduces the risk of childhood leukemia.