量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum Science and Technology.
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The risk of developing secondary cancer after radiotherapy, especially after treatment of childhood cancers, remains a matter of concern. The high biological effects of carbon-ion radiation have enabled powerful radiotherapy, yet the approach is commonly restricted to the treatment of adults. The present study is aimed to investigate the effect of carbon-ion irradiation in childhood on breast carcinogenesis.
We irradiated female Sprague-Dawley rats of various ages (embryonic days 3, 13 and 17, and 1, 3, 7 and 15 weeks after birth) with 137Cs gamma rays or a 290-MeV/u monoenergetic carbon-ion beam (linear energy transfer, 13 keV/um). All animals were screened weekly for mammary carcinoma by palpation until they were 90 weeks old.
Irradiation of fetal and mature (15-week-old) rats with either radiation source at a dose of 0.2 or 1 Gy did not substantially increase the hazard ratio compared to the non-irradiated group. Dose responses (0.2-2.0 Gy) to gamma rays were similar among the groups of rats irradiated 1, 3 and 7 weeks after birth. The effect of carbon ions increased along with the age at the time of irradiation, indicating relative biological effectiveness values of 0.2 [-0.3, 0.7], 1.3 [1.0, 1.6] and 2.8 [1.8, 3.9] (mean and 95% confidence interval) for animals that were 1, 3 and 7 weeks of age, respectively.
Our findings imply that carbon-ion therapy may be associated with a risk of secondary breast cancer in humans, the extent of which may depend on the age of the patient at the time of irradiation.
会議概要（会議名, 開催地, 会期, 主催者等）
Heavy Ion in Therapy and Space Radiation Symposium 2013
Mammary carcinogenesis after exposure of fetal, neonatal, juvenile and adult rats to gamma rays and carbon ions.
