According to the study, published in the Journal of National Cancer Institute, the incidence of NHL has increased significantly over the last 5 decades. Although the overall incidence began to stabilize among adults, it has continued growing in children, adolescents, and young adults.
As a result, Casey Crump, M.D., Ph.D., of the Department of Medicine at Stanford University and colleagues set out to determine the cause of NHL incidence in children, adolescents, and young adults.
The team analyzed 3.5 million Swedes born between 1973-2008, who received follow-up for NHL incidence till 2009. The researchers attained data on perinatal and family characteristics and NHL diagnoses via birth and cancer registries and then evaluated association of those characteristics with the risk of NHL using Cox proportional hazard models.
In adolescents, the team found that utero conditions and genetics contributed to the incidence of NHL, with family history of NHL in either a sibling or parent being the strongest association. Other factors, including older maternal age, low birth order, and high fetal growth also contributed in incidence rates.
In children under 15 years of age, male gender was found to be linked with NHL incidence, but not with later onset of NHL.
The researchers said:
"These findings suggest several heterogeneous mechanisms including possible growth factor pathways in utero, immunologic effects of delayed infectious exposures, as well as other unmeasured environmental and genetic factors.
Further elucidation of these risk factors may facilitate the identification of high-risk individuals at young ages and potential enable earlier detection and treatment."
In an associated report, William F. Anderson, M.D., M.P.H., and Benjamin Emmanuel, MPH, of the National Cancer Institute at the Division of Cancer Epidemiology and Genetics, highlight that although this is a "well-performed national cohort study," there are certain limitations including: the unavailability of host and environmental risk factors, such as environmental contaminants and radiation.
They conclude that the study's "large-scale and population-based design minimized selection bias and maximized generalizable conclusions for associations between NHL in early life and family history, high fetal growth weight, older maternal age, low birth order, and male sex."