Hill S A, Smith K A, Williams K B, Denekamp J
Cancer Research Campaign Gray Laboratory, Mount Vernon Hospital, Northwood, Middlesex, U.K.
Radiother Oncol. 1989 Oct;16(2):129-37. doi: 10.1016/0167-8140(89)90030-3.
The sparing effect of dividing a radiation treatment into many small fractions is different for acutely responding tissues and those which have delayed expression of injury. We have used the Tumour Bed Effect assay (TBE) to investigate the influence of the time of damage expression on the response of the normally quiescent subcutaneous stroma. Implanted tumour cells provide an angiogenic stimulus which forces the vasculature to proliferate. The subcutaneous stroma of the mouse dorsum was irradiated with one to 32 equal fractions of X-rays, followed by a top-up dose of neutrons. CaNT cells were implanted into the treated site either within 3 days or not until 6 months after irradiation, to stimulate the expression of latent injury. The dose-response curves obtained for tumour growth in irradiated sites were much steeper at 1 to 3 days than at 6 months, suggesting some sort of repair of damage during this period. There was no suggestion that repair occurred preferentially after low doses per fraction and the alpha/beta ratio remained unchanged when the expression of stromal injury was delayed. The time of damage expression therefore seems unlikely to explain the difference in the alpha/beta ratios measured for early and late responding tissues. Rather, it seems to be determined by the proliferative status of the tissue at the time of irradiation.
将放射治疗分成许多小剂量分割的 sparing 效应，对于急性反应组织和那些损伤表现有延迟的组织是不同的。我们使用肿瘤床效应试验（TBE）来研究损伤表现时间对正常静止的皮下基质反应的影响。植入的肿瘤细胞提供血管生成刺激，促使脉管系统增殖。用 1 到 32 等份的 X 射线照射小鼠背部的皮下基质，随后给予一次补充剂量的中子。在照射后 3 天内或直到 6 个月后，将 CaNT 细胞植入治疗部位，以刺激潜在损伤的表达。在照射部位获得的肿瘤生长剂量反应曲线在 1 至 3 天时比在 6 个月时陡峭得多，表明在此期间某种程度的损伤修复发生了。没有迹象表明在低剂量分割后优先发生修复，并且当基质损伤的表达延迟时，α/β 比值保持不变。因此，损伤表现时间似乎不太可能解释早期和晚期反应组织测量的 α/β 比值差异。相反，它似乎由照射时组织的增殖状态决定。
