Appold S, Baumann M, Petersen C, Horn K, Eichhorn F
Klinik und Poliklinik für Strahlentherapie und Radioonkologie, Medizinische Fakultät Carl Gustav Carus, Technischen Universität Dresden.
Strahlenther Onkol. 1998 Jun;174(6):315-9. doi: 10.1007/BF03038546.
It has been suggested that tumors respond differently after irradiation with 10 or more fractions than with less fractionated regimens and that extrapolation from experiments with only a few fractions to "curative" regimens may be invalid. To test this hypothesis, we compared hypofractionated-accelerated treatments with "curative" fractionation schedules in human squamous cell carcinoma in nude mice.
FaDu tumors were transplanted subcutaneously into the hindleg of NMRI nu/nu mice. TCD50 values, i.e., the dose necessary to control 50% of the tumors locally, were determined after irradiation under ambient blood flow conditions with 5 and 10 fractions in 5 days, 10 fractions in 10 days, and 30 fractions in 15 days, 6 weeks or 10 weeks.
TCD50 values of the hypofractionated regimens were not significantly different and varied from 41 to 46 Gy. The number of fractions given in the same overall time had no measurable effect on local tumor control. The TCD50 after 30 fractions in 6 weeks was 30 Gy higher than after the hypofractionated regimens. This effect was caused by a substantial increase of TCD50 with overall treatment time, the dose recovered per day was 0.82 Gy (95% CI 0.66; 0.96). alpha/beta eff determined from all data was 58 Gy (13; infinite).
The results of the present study compare well with our previous findings after different "curative" fractionation schedules in the same tumor. Thus, our study does not support that tumors respond differently after application of 10 or more fractions compared to less fractionated regimens. The biological mechanisms that govern the radiation response of FaDu tumors appear to be the same for hypofractionated-accelerated and "curative" regimens. Since only one tumor was investigated, these results cannot be generalized at the present time.
有人提出，肿瘤在接受10次或更多次分割照射后的反应与较少分割方案不同，并且从仅少数几次分割的实验推断至“根治性”方案可能无效。为了验证这一假设，我们在裸鼠的人鳞状细胞癌中比较了超分割加速治疗与“根治性”分割方案。
将FaDu肿瘤皮下移植到NMRI nu/nu小鼠的后肢。在环境血流条件下，分别于5天内给予5次和10次分割、10天内给予10次分割、15天、6周或10周内给予30次分割照射后，测定TCD50值，即局部控制50%肿瘤所需的剂量。
超分割方案的TCD50值无显著差异，范围为41至46 Gy。在相同总时间内给予的分割次数对局部肿瘤控制没有可测量的影响。6周内给予30次分割后的TCD50比超分割方案高30 Gy。这种效应是由于TCD50随总治疗时间大幅增加所致，每天恢复的剂量为0.82 Gy（95%CI 0.66；0.96）。根据所有数据确定的α/βeff为58 Gy（13；无穷大）。
本研究结果与我们之前在同一肿瘤中采用不同“根治性”分割方案后的发现相符。因此，我们的研究不支持肿瘤在接受10次或更多次分割照射后的反应与较少分割方案不同这一观点。对于超分割加速和“根治性”方案，控制FaDu肿瘤放射反应的生物学机制似乎相同。由于仅研究了一种肿瘤，目前这些结果尚不能推广。
