LOW DOSE RADIATION AND LEUKEMIA RISK

 Cumulative exposure to low levels of ionizing radiation is associated with an increased risk of developing leukemia, according to a new analysis.

There is substantial evidence linking moderate or high doses of ionizing radiation, particularly in childhood, to leukemia risk, write Dr. Mark P. Little of the National Institutes of Health, in Bethesda, Maryland, and colleagues in The Lancet Haematology, online July 16.

To examine whether this might also be true of low doses, the team studied data on more than 262,000 people enrolled in nine cohorts between 1915 and 2004. All had been exposed to less than 100 mSv and were younger than 21 years at first irradiation.

The mean follow-up was 19.63 years and the mean cumulative estimated individual active bone marrow dosage was 19.6 mSv.

There were 154 myeloid malignancies and 40 cases of acute lymphoblastic leukemia. The grouped categories used for comparisons, included 139 cases of acute leukemia and 221 cases of all leukemia, excluding chronic lymphocytic leukemia because there is "little evidence" of its association with radiation.

The fitted relative risk at 100 mSv was 3.09 for acute myeloid leukemia and myelodysplastic syndromes combined. It was 2.56 for acute myeloid leukemia and 5.66 for acute lymphoblastic leukemia. Moreover, for acute myeloid leukemia and myelodysplastic syndromes combined, as well as acute lymphoblastic leukemia, the risk continued to be significantly increased at doses of less than 50 mSv.

Overall, the researchers write, there were "were few indications of between-cohort heterogeneity or departure from linearity."

These findings, Dr. Little told Reuters Health by email, "suggest that there is risk of leukaemia associated with low-level exposure to radiation. Since most exposures to workers and the public are from low doses, the present study, among others, suggests that the current system of radiological protection is prudent and not overly protective."

The results "also add weight to efforts already underway (such as by the Image Gently Campaign) to minimize the use of diagnostic radiological imaging, particularly in children, wherever possible."

Dr. Christopher S. Hourigan, also of the National Institutes of Health in Bethesda, who co-wrote an accompanying editorial, told Reuters Health by email, "While we continue to look for better ways to treat acute leukemia, we are also extremely interested in understanding inherited and acquired factors that may be helpful in preventing these blood cancers."

"This new work," he concluded, "provides important evidence in support of efforts over the past decade to minimize radiation exposure to children during essential medical procedures."

SOURCE: https://bit.ly/2v0tOmi and https://bit.ly/2KdBXbR