Cigarette smoke contains dozens of well-established human carcinogens and it is known to increase the risk of various adult cancers including myeloid leukemia.  Likewise, parental cigarette smoking may also increase the risk of childhood leukemia.

CIRCLE Director, Dr. Catherine Metayer, and her colleagues have evaluated the risk of childhood leukemia associated with parental smoking in the California Childhood Leukemia Study.  The study included 902 children with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) and 1139 control children without leukemia. Parental cigarette smoking histories were obtained via interviews, primarily with the biological mother.  The study found that a child whose father smoked before conception was at an increased risk of leukemia compared to a child with a nonsmoking father.  The risk of leukemia was greatest when preconception paternal smoking was combined with a child’s exposure to passive smoking after birth, and was higher for ALL with certain chromosome translocations.

It is challenging to obtain accurate histories of maternal smoking during pregnancy using interviews, because mothers may have trouble remembering their past smoking habits or they may be reluctant to discuss their smoking habits during pregnancy.  Moreover, maternal smoking causes other negative birth outcomes, which obscure our ability to measure leukemia risk.  Both of these factors could help explain why we did not observe an association between maternal smoking during pregnancy and childhood leukemia  overall.  Interestingly, maternal smoking during pregnancy and during breastfeeding increased the risks of childhood ALL with chromosome deletions, but not RAS mutations.

Childhood leukemia is a heterogeneous cancer, and our study suggests that the relationship between parental smoking and childhood leukemia is complex, depending on the molecular leukemia subtypes.  The full articles are available here.

The Childhood Leukemia International Consortium (CLIC) strengthened the evidence of a modest association between paternal smoking and the second-most common subtype of childhood leukemia — acute myeloid leukemia (AML) — using a pooled analysis of 1,330  children with AML, the largest study to date.  We found dose-response relationships, meaning that leukemia risk increased with an increasing number of cigarettes the father smoked. No associations were observed between AML and maternal smoking any time before or after birth, except possibly for Latina mothers participating in the CLIC studies from California and Washington states, Mexico, and Costa Rica.

References:

de Smith AJ, Kaur M, Gonseth S, et al. Correlates of Prenatal and Early-Life Tobacco Smoke Exposure and Frequency of Common Gene Deletions in Childhood Acute Lymphoblastic Leukemia. Cancer Res. 2017;77(7):1674-1683. doi:10.1158/0008-5472.CAN-16-2571

Kaur M, de Smith AJ, Selvin S, et al. Tobacco Smoke and Ras Mutations Among Latino and Non-Latino Children with Acute Lymphoblastic Leukemia. Arch Med Res. 2016;47(8):677-683. doi:10.1016/j.arcmed.2016.11.016