Hamatani and colleagues from across Japan made a comparison between adult-onset papillary thyroid cancers with RET/PTC rearrangements and those with a BRAF mutation. More than 70 percent of adult onset papillary thyroid cancer in non-exposed patients is associated with mutations in the BRAF gene.
The researchers looked at the genetic profile of cancer patients in the RERF's follow-up study--50 patients who were exposed to atomic bomb radiation and 21 patients who were not. Three factors were found to be independently associated with the development of adult-onset papillary thyroid cancer with RET/PTC rearrangements. They were greater radiation dose, shorter time elapsed since radiation exposure, and younger age at the time of the bombings, Hamatani says.
"That means that a younger person living close to the bombing site would be more likely to have adult onset thyroid cancer having RET/PTC rearrangements," he said. "This is the first time this has been shown."
The findings also suggest that in childhood papillary thyroid cancer RET/PTC rearrangements may be much less clearly associated with radiation exposure, compared with adult-onset cancer, because RET/PTC rearrangements are frequent in childhood papillary thyroid cancer patients regardless of history of radiation exposure.
The researchers do not know exactly how radiation is involved in the occurrence of RET/PTC rearrangements. "It could be either by direct DNA damage or by other pathways such as a result of radiation-induced genomic instability," Hamatani said.
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| Contact: Jeremy Moore Jeremy.moore@aacr.org 267-646-0557 American Association for Cancer Research Source:Eurekalert |