Ando Koichi, Koike Sachiko, Oohira Chisa, Ogiu Toshiaki, Yatagai Fumio
Heavy-Ion Radiobiology Research Group, National Institute of Radiological Sciences, Chiba, Japan.
J Radiat Res. 2005 Jun;46(2):185-90. doi: 10.1269/jrr.46.185.
Tumor induction in mice legs that were locally irradiated with carbon ions was compared to tumor induction by gamma rays after single and fractionated irradiation. A total of 250 tumors were induced in 1104 mice that received carbon-ion doses of 5 through 65 Gy. A total of 77 tumors were induced in 371 mice that received gamma-ray doses of 45 through 95 Gy. Of 91 carbon-ion induced tumors examined histologically, 97 percent were malignant, and sarcomas such as malignant fibrous histiocytoma (47%) and fibrosarcoma (32%) were most frequently observed. Malignant fibrous histiocytoma was also the most frequently observed tumor (12 out of 20 tumors; 60%) after gamma-ray irradiation, followed by carcinomas (25%) such as adenocarcinoma and squamous cell carcinoma. Neither dose fractionation nor linear energy transfer affected tumor induction for carbon ions and gamma rays. Dose responses were linear for carbon ions and gamma rays, and showed no saturation up to 65 Gy of carbon ions and 95 Gy of gamma rays. The relative biological effectiveness of carbon ions was 2.2 for tumor induction and 1.9 for early skin reaction. We conclude that risk of secondary tumor induction by carbon-ion radiotherapy would not be seriously higher than anticipated.
将局部接受碳离子照射的小鼠腿部肿瘤诱发情况与单次及分次照射后γ射线诱发肿瘤的情况进行了比较。在接受5至65 Gy碳离子剂量的1104只小鼠中，共诱发了250个肿瘤。在接受45至95 Gyγ射线剂量的371只小鼠中，共诱发了77个肿瘤。在组织学检查的91个碳离子诱发肿瘤中，97%为恶性，最常观察到的是恶性纤维组织细胞瘤（47%）和纤维肉瘤（32%）等肉瘤。恶性纤维组织细胞瘤也是γ射线照射后最常观察到的肿瘤（20个肿瘤中有12个；60%），其次是腺癌和鳞状细胞癌等癌（25%）。剂量分割和线性能量传递对碳离子和γ射线诱发肿瘤均无影响。碳离子和γ射线的剂量反应呈线性，在65 Gy碳离子和95 Gyγ射线时均未显示饱和。碳离子诱发肿瘤的相对生物效应为2.2，早期皮肤反应的相对生物效应为1.9。我们得出结论，碳离子放射治疗诱发继发性肿瘤的风险不会比预期严重更高。
