Bhattathiri V N, Bindu L, Remani P, Chandralekha B, Davis C A, Nair M K
Department of Radiotherapy, Regional Cancer Centre, Trivandrum, India.
Radiother Oncol. 1996 Nov;41(2):139-42. doi: 10.1016/s0167-8140(96)01810-5.
The micronucleus test, generally done in cultured tumour cells irradiated in vitro, has not gained wide acceptance in predicting human cancer radiosensitivity. The purpose of this study was to see if micronucleus assay by serial scrape smear cytology can predict oral cancer radiosensitivity.
Forty nine oral cancer patients given radiotherapy (60 Gy/25 fractions/5 weeks) form the study population. Serial scrape smears were taken from their tumours before treatment and after delivery of 2, 5, 8 and 12 fractions, stained by Giemsa and the number of micronucleated cells (MNC) noted. The patients were grouped to those who developed tumour recurrence ('Resistant') and those who did not ('Sensitive'), and the pattern of micronucleus induction compared.
Both groups of tumours had MNC even before treatment, with statistically significant dose-related increase with radiotherapy. The sensitive group had a higher mean increase in MNC count than the resistant group (6.1 times and 3.6 times the pre-treatment value, respectively) and better correlation with dose (r = 0.54 vs. 0.43). The increase in MNC count occurred earlier in the resistant group than in the sensitive, the TMNC (time for the pre-treatment value to double) being 3.3 days and 7.6 days, respectively. Also, the resistant group showed a plateauing of the MNC count which the sensitive group lacked.
The higher MNC induction in the sensitive tumours suggests the usefulness of the assay as a test of radiosensitivity. The differing patterns of MNC increase suggest that differences in proliferation rate is an important cause of tumour failure. Serial cytological assay of micronucleus induction can identify both radiosensitivity and proliferation characteristics of tumours, and thus may turn out to be a useful test of radiocurability.
微核试验通常在体外照射的培养肿瘤细胞中进行，在预测人类癌症放射敏感性方面尚未得到广泛认可。本研究的目的是探讨通过连续刮片细胞学进行微核试验是否能够预测口腔癌的放射敏感性。
四十九名接受放射治疗（60 Gy/25次分割/5周）的口腔癌患者构成了研究群体。在治疗前以及给予2、5、8和12次分割照射后，从他们的肿瘤处获取连续刮片，用吉姆萨染色并记录微核细胞（MNC）的数量。将患者分为发生肿瘤复发的患者（“抗性”）和未复发的患者（“敏感”），并比较微核诱导模式。
两组肿瘤在治疗前就已经存在微核细胞，放疗后微核细胞数量有统计学意义的剂量相关增加。敏感组微核细胞计数的平均增加高于抗性组（分别为治疗前值的6.1倍和3.6倍），并且与剂量的相关性更好（r = 0.54对0.43）。抗性组微核细胞计数的增加比敏感组更早出现，微核细胞计数翻倍时间（TMNC）分别为3.3天和7.6天。此外，抗性组微核细胞计数出现平台期，而敏感组没有。
敏感肿瘤中较高的微核诱导表明该试验作为放射敏感性测试的有用性。微核增加的不同模式表明增殖率的差异是肿瘤治疗失败的重要原因。微核诱导的连续细胞学试验可以识别肿瘤的放射敏感性和增殖特征，因此可能成为放射可治愈性的有用测试。
