Würschmidt F, Vogler H, Beck-Bornholdt H P
Institute of Biophysics and Radiobiology, University of Hamburg, F.R.G.
Int J Radiat Oncol Biol Phys. 1988 Mar;14(3):497-502. doi: 10.1016/0360-3016(88)90266-0.
The influence of the number of fractions on tumor and skin response to fractionated irradiation was studied. R1H rhabdomyosarcomas of the rat (volume doubling time 3 days) were irradiated with 6, 18, 30, or 42 fractions in 6 weeks. Total doses of 45, 60, or 75 Gy were applied in each fractionation scheme, that is, the dose per fraction ranged from 1.07 to 12.5 Gy. Tumor response was assessed by tumor control probability and tumor net growth delay. A clearcut reduction of skin damage was observed with increasing number of fractions, whereas the tumor response was found to be the same whether the dose was given in 6, 18, 30, or 42 fractions. Thus, the fractionation regimens were more effective than expected from calculations based on single-dose in situ survival curves. This result can be explained by assuming that the clonogenic tumor cells become less hypoxic with increasing number of fractions. Since normal tissue damage decreases with increasing number of fractions, the therapeutic gain may be improved by applying a greater number of fractions.
研究了分次照射的次数对肿瘤及皮肤对分次放疗反应的影响。用6周时间对大鼠的R1H横纹肌肉瘤（体积倍增时间为3天）进行6次、18次、30次或42次照射。每种分次照射方案的总剂量为45 Gy、60 Gy或75 Gy，即每次照射剂量范围为1.07 Gy至12.5 Gy。通过肿瘤控制概率和肿瘤净生长延迟来评估肿瘤反应。随着分次次数的增加，观察到皮肤损伤明显减轻，而无论剂量是分6次、18次、30次还是42次给予，肿瘤反应均相同。因此，分次照射方案比基于单剂量原位存活曲线计算所预期的更有效。该结果可以通过假设随着分次次数增加，肿瘤克隆源性细胞的缺氧程度降低来解释。由于正常组织损伤随着分次次数的增加而减少，增加分次次数可能会提高治疗增益。
