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||RET/PTC and PAX8/PPARÎ³ chromosomal rearrangements in post-Chernobyl thyroid cancer and their association with iodine-131 radiation dose and other characteristics.
||Leeman-Neill RJ, Brenner AV, Little MP, Bogdanova TI, Hatch M, Zurnadzy LY, Mabuchi K, Tronko MD, Nikiforov YE
||2013 May 15
||BACKGROUND: Childhood exposure to iodine-131 from the 1986 nuclear accident in Chernobyl, Ukraine, led to a sharp increase in papillary thyroid carcinoma (PTC) incidence in regions surrounding the reactor. Data concerning the association between genetic mutations in PTCs and individual radiation doses are limited. METHODS: Mutational analysis was performed on 62 PTCs diagnosed in a Ukrainian cohort of patients who were < 18 years old in 1986 and received 0.008 to 8.6 Gy of (131) I to the thyroid. Associations between mutation types and (131) I dose and other characteristics were explored. RESULTS: RET/PTC (ret proto-oncogene/papillary thyroid carcinoma) rearrangements were most common (35%), followed by BRAF (15%) and RAS (8%) point mutations. Two tumors carrying PAX8/PPARÎ³ (paired box 8/peroxisome proliferator-activated receptor gamma) rearrangement were identified. A significant negative association with (131) I dose for BRAF and RAS point mutations and a significant concave association with (131) I dose, with an inflection point at 1.6 Gy and odds ratio of 2.1, based on a linear-quadratic model for RET/PTC and PAX8/PPARÎ³ rearrangements were found. The trends with dose were significantly different between tumors with point mutations and rearrangements. Compared with point mutations, rearrangements were associated with residence in the relatively iodine-deficient Zhytomyr region, younger age at exposure or surgery, and male sex. CONCLUSIONS: These results provide the first demonstration of PAX8/PPARÎ³ rearrangements in post-Chernobyl tumors and show different associations for point mutations and chromosomal rearrangements with (131) I dose and other factors. These data support the relationship between chromosomal rearrangements, but not point mutations, and (131) I exposure and point to a possible role of iodine deficiency in generation of RET/PTC rearrangements in these patients.