Breast milk protected infants from hematologic neoplasms
A large cohort study of more than 300,000 children in Denmark found that exclusive breastfeeding for at least three months of a child's life was associated with a reduced risk of developing hematologic oncology, particularly acute lymphoblastic leukemia. However, this strategy did not affect the risk of tumors in the central nervous system and solid tumors. The results of the study are published in JAMA Network Open.
In most cases, doctors and scientists cannot determine the cause of tumor development in children, making it impossible to develop effective cancer prevention methods for them. However, some studies, including meta-analyses, have shown that children who were breastfed for at least six months had about a 20 percent lower risk of developing acute lymphoblastic leukemia compared to those who were breastfed for a shorter period or not breastfed at all. In addition, other studies have shown that breastfeeding reduces the risk of acute myeloid leukemia, Hodgkin's lymphoma, and neuroblastoma.
This effect of breastfeeding has a sound biological basis, as breast milk plays a crucial role in shaping the gut microbiome and immune system of the child. Accordingly, it is believed that aberrant immune responses to infectious stimuli significantly affect the development of B-cell precursors, which most often become the morphologic basis of acute lymphoblastic leukemia. In addition, studies using mouse models have shown a direct link between the gut microbiome and the pathogenesis of this type of tumor. However, it is not completely clear what duration of breastfeeding can be considered optimal for tumor prevention.
A team of scientists led by Signe Holst Søegaard from the Danish Cancer Institute has tried to find out. They conducted a population-based cohort study involving 309473 children born in Denmark between 2005 and 2018. For all children, information on the duration of exclusive breastfeeding was available. During 1679635 person-years of follow-up, a total of 332 children were diagnosed with tumors (mean age at diagnosis, 4.24 years): 124 children were diagnosed with tumors of the hematopoietic system, 44 with tumors of the central nervous system, 80 had solid tumors, and 84 had other malignancies.
Among the children diagnosed with hematologic tumors, 81 had acute lymphoblastic leukemia, of which 74 had B-lymphocyte precursors. Another seven children were diagnosed with acute myeloid leukemia, and the rest with Hodgkin's lymphoma. The most commonly diagnosed tumors of the central nervous system were astrocytoma, ependymoma, and intracranial and intraspinal fetal tumors. Renal tumors, neuroblastoma, and soft tissue sarcomas were the most common solid tumors.
The log-linear trend-adjusted relative risk of oncohematologic disease was 0.91 and 0.90 for B-cell leukemia when comparing breastfed and non-breastfed children. In a dichotomized analysis comparing shorter periods of exclusive breastfeeding and feeding for three months, a longer period of breastfeeding was associated with a reduced risk of hematologic disease (relative risk 0.66), and this reduction was more strongly associated with a reduced risk of B-cell leukemia. However, the risk of central nervous system tumors, solid tumors, and neuroblastomas did not depend exclusively on the duration of breastfeeding.
The results of this study support previous findings on the preventive potential of breastfeeding for hematologic cancers. However, in this work, the researchers found that even three months of exclusive breastfeeding has this potential. In the future, doctors expect to find out the magnitude of the protective effect of each month of breastfeeding.