Ang K K, Xu F X, Vanuytsel L, van der Schueren E
Radiat Res. 1985 Jan;101(1):162-9.
The repopulation kinetics of the irradiated lip mucosa of mice has been investigated. Split-dose experiments showed that, in this tissue, repopulation starts within 3 days after the first irradiation and increases exponentially within 10 days. To assess the relative importance of protraction and distribution of irradiations as a function of time, 10 fractions were given in (1) 3 days (three irradiations per day with a 4-hr interval), (2) 11 days (daily fractions), or (3) two short courses, each consisting of five fractions given in 1.5 days separated by a rest period of 8 days, with an overall time of 11 days. The results show that by protracting the treatment from 3 to 11 days (with daily irradiations) repopulation accounts for recovery of approximately 13 Gy. Delivering the radiation in two short courses separated by a rest period leads to an additional recovery of approximately 5 Gy. The most plausible explanation for this observation is that repopulation is much more efficient during the rest period between the two courses than during continuous daily irradiation. Although the regimen of two short courses with a rest period spares the acute reaction, it will not enhance the late tolerance. Before thorough knowledge about the repopulation kinetics of the tumors can be gained, caution should be observed for indiscriminate use of split-course multiple-fraction-per-day (MFD) regimens for treating various tumors.
已对小鼠受照射唇部黏膜的再增殖动力学进行了研究。分次照射实验表明，在该组织中，再增殖在首次照射后3天内开始，并在10天内呈指数增长。为了评估照射时间延长和分布随时间变化的相对重要性，分别在以下三种情况下给予10次分次照射：（1）3天内（每天照射3次，间隔4小时）；（2）11天内（每天1次分次照射）；或（3）两个短疗程，每个疗程由1.5天内给予的5次分次照射组成，中间间隔8天的休息期，总时间为11天。结果表明，将治疗时间从3天延长至11天（每日照射），再增殖可使约13 Gy的损伤得以恢复。采用两个短疗程并间隔休息期进行照射可额外恢复约5 Gy。对此观察结果最合理的解释是，两个疗程之间的休息期内再增殖比连续每日照射时更有效。虽然两个短疗程并间隔休息期的方案可减轻急性反应，但不会提高晚期耐受性。在全面了解肿瘤再增殖动力学之前，对于不加区分地使用每天多次分次的分割疗程方案治疗各种肿瘤应谨慎。
