Misa Imaizumi, MD, PhD; Waka Ohishi, MD, PhD; Eiji Nakashima, PhD; Nobuko Sera, MD, PhD; Kazuo Neriishi, MD, PhD; Michiko Yamada, MD, PhD; Yoshimi Tatsukawa, MD, PhD; Ikuno Takahashi, MD, PhD; Saeko Fujiwara, MD, PhD; Keizo Sugino, MD, PhD; Takao Ando, MD, PhD; Toshiro Usa, MD, PhD; Atsushi Kawakami, MD, PhD; Masazumi Akahoshi, MD, PhD; Ayumi Hida, MD, PhD
Abstract
Importance Few studies have evaluated the association of radiation dose with thyroid nodules among adults exposed to radiation in childhood.
Objective To evaluate radiation dose responses on the prevalence of thyroid nodules in atomic bomb survivors exposed in childhood.
Design, Setting, and Participants This survey study investigated 3087 Hiroshima and Nagasaki atomic bomb survivors who were younger than 10 years at exposure and participated in the thyroid study of the Adult Health Study at the Radiation Effects Research Foundation. Thyroid examinations including thyroid ultrasonography were conducted between October 2007 and October 2011, and solid nodules underwent fine-needle aspiration biopsy. Data from 2668 participants (86.4% of the total participants; mean age, 68.2 years; 1213 men; and 1455 women) with known atomic bomb thyroid radiation doses (mean dose, 0.182 Gy; median dose, 0.018 Gy; dose range, 0-4.040 Gy) were analyzed.
Main Outcomes and Measures The prevalence of all thyroid nodules having a diameter of 10 mm or more (consisting of solid nodules [malignant and benign] and cysts), prevalence of small thyroid nodules that were less than 10 mm in diameter detected by ultrasonography, and atomic bomb radiation dose-responses.
Results Thyroid nodules with a diameter of 10 mm or more were identified in 470 participants (17.6%): solid nodules (427 cases [16.0%]), malignant tumors (47 cases [1.8%]), benign nodules (186 cases [7.0%]), and cysts (49 cases [1.8%]), and all were significantly associated with thyroid radiation dose. Excess odds ratios per gray unit were 1.65 (95% CI, 0.89-2.64) for all nodules, 1.72 (95% CI, 0.93-2.75) for solid nodules, 4.40 (95% CI, 1.75-9.97) for malignant tumors, 2.07 (95% CI, 1.16-3.39) for benign nodules, and 1.11 (95% CI, 0.15-3.12) for cysts. The interaction between age at exposure and the dose was significant for the prevalence of all nodules (P = .003) and solid nodules (P < .001), indicating that dose effects were significantly higher with earlier childhood exposure. No interactions were seen for sex, family history of thyroid disease, antithyroid antibodies, or seaweed intake. No dose-response relationships were observed for small (<10-mm diameter) thyroid nodules.
Conclusions and Relevance Radiation effects on thyroid nodules exist in atomic bomb survivors 62 to 66 years after their exposure in childhood. However, radiation exposure is not associated with small thyroid nodules.
http://archinte.jamanetwork.com/article.aspx?articleID=2038986
今泉美彩、大石和佳、中島栄二、世羅至子、錬石和男、山田美智子、立川佳美、高橋郁 乃、藤原佐枝子、杉野圭三、安藤隆雄、宇佐俊郎、川上 純、赤星正純、飛田あゆみ
“Association of Radiation Dose With Prevalence of Thyroid Nodules Among Atomic Bomb Survivors Exposed in Childhood (2007-2011)” JAMA Intern Med 2015 (February); 175(2):228-236 （doi: 10.1001/jamainternmed.2014.6692）
今回の調査で明らかになったこと 小児期（10 歳未満）に被曝した原爆被爆者の 62－66 年後の甲状腺調査において、甲状腺結節（径 10mm 以上または甲状腺結節術後）の有病率* は原爆による甲状腺被曝線 量と有意な関連を認めたが、径 10mm 未満の小結節の有病率は関連を認めなかった。 〔注〕* 有病率とは、最初に罹患した時期とは無関係に、ある時点（検査時）において 集団の中で疾病に罹患している人の割合をいう。
解 説 1958 年から 2 年に 1 度の健康診断により広島・長崎の原爆被爆者の健康状態を追跡 している成人健康調査の参加者のうち、10 歳未満の小児期に被曝した参加者を対象と して、甲状腺結節と原爆放射線の関連を調査した。 〔注〕甲状腺結節とは悪性、良性問わず甲状腺に見られるしこりの総称で、超音波検査 で観察すると大きく分けてのう胞と充実性結節の 2 種類が認められる。のう胞はほぼ 良性で、充実性結節は悪性腫瘍（主にがん）と良性結節に分類される。良性結節には 良性腫瘍の他、過形成や甲状腺炎に伴う結節などがある。通常、悪性腫瘍以外は治療 の必要はないが、大きい結節で圧迫症状があったり、悪性の可能性が否定できない場 合などに治療することがある。本調査では甲状腺結節を、臨床的に問題となりやすい 比較的大きい甲状腺結節（径 10mm 以上または甲状腺結節術後）について重点的に検 討し、さらに臨床的に問題となりにくい径 10mm 未満の小結節についても検討を加えた。
