Individualization of Radiotherapy by Micronucleus Test

肿瘤细胞放射敏感性的微小差异对肿瘤的最终控制率有很大影响。因此，在放射治疗开始之前，可以检测肿瘤细胞和正常组织的放射敏感性，并且可以改变每个患者的剂量分数和总剂量。本文报告了14例食管癌手术标本培养的放射敏感性。培养肿瘤细胞悬液，数天后用50 KVp X线照射。然后用细胞松弛素B继续培养48或72小时。加入该试剂以鉴定照射后通过有丝分裂期的细胞。细胞松弛素B抑制细胞质裂解而不干扰核分裂。这样的细胞很容易识别。将肿瘤细胞固定，制备用于微核试验的显微玻片。碘化丙啶染色后在荧光显微镜下观察微核，微核的剂量反应曲线按线性二次模型进行分析。14例食管癌的α/β值范围为1.5至无限大小。与β值相比，α值在肿瘤之间的差异更大。氧增强比（OER）也有很宽的范围（1.3-2.7），特别是在低剂量范围（0-2戈伊）。为了研究不同肿瘤患者正常组织放射敏感性的差异，我们在3个不同品系的小鼠（Balb/C，A/J，C_3H/He）中进行了研究。淋巴细胞微核试验与成纤维细胞、肠腺细胞辐射敏感性的相关性研究。3种不同品系小鼠淋巴细胞的辐射敏感性顺序与成纤维细胞和肠腺细胞的辐射敏感性顺序完全一致。

A small difference of the radiosensitivity of tumor cells asserts great influence on the final control rate of tumors. Therefore, it is ideal that radiosensitivities of tumor cells and normal tissues could be examined before the start of radiotherapy, and dose fraction, total dose could be changed on each patient. We have examined the radiosensitivity in 14 different esophageal cancers cultured from surgical specimens The tumor cell suspensions were cultured and several days after, 50 KVp xrays were irradiated. Thereafter the culture was continued for 48 or 72 hours with cytochalasin B. This agent was added to identify the cells passed through mitotic phase after irradiation. Cytochalasin B inhibits cytoplasmic cleavage without interfering nuclear division. Therefore, such cells could be easily identified. The tumor cells were fixed and microslides for micronucleus assay were prepared. The micronuclei were observed by fluorescence microscope after staining with propidium iodide.The dose response curves of micronuclei were analyzed according to linear-quadratic model. The alpha/beta values among 14 esophageal cancers ranged from 1.5 to unlimited size. Alpha values differed more largely from tumor to tumor compared with beta values. Oxygen enhancement ratios (OERs) also ha wide range (1.3-2.7) especially in low radiation dose range (0-2 Gy). The differences in tumor cell radiosensitivity were clearly demonstrated.To examine the difference of normal tissue radiosensitivity in individual patient, we have studied that in 3 different strain of mice (Balb/C, A/J, C3H/He). The correlation between the radiosensitivity of lymphocytes determined by micronucleus assay and those of fibroblasts and intestinal crypt cells. The order of radiosensitiity of lymphocytes obtained in 3 different strain of mice was accurately repeated in those of fibroblasts and intestinal crypt cells.