Altman Michael B, Stinauer Michelle A, Javier Desler, Smith Brett D, Herman Lauren C, Pytynia Matthew L, Aydogan Bulent, Pelizzari Charles A, Chmura Steven J, Roeske John C
Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL 60657, USA.
Int J Radiat Oncol Biol Phys. 2009 Nov 15;75(4):1240-6. doi: 10.1016/j.ijrobp.2009.06.076.
To experimentally validate how temporal modification of the applied dose pattern within a single fraction of radiation therapy affects cell survival.
Using the linear-quadratic model, we have previously demonstrated that the greatest difference in cell survival results from comparing a temporal dose pattern delivering the highest doses during the middle of a fraction and the lowest at the beginning and end ("Triangle") to one with the lowest doses at the middle and the highest at the beginning and end ("V-shaped"). Also, these differences would be greatest in situations with low alpha/beta and large dose/fraction and fraction length. Two low (WiDr, PC-3) and one high (SQ-20B) alpha/beta cell lines were irradiated in six-well plates with 900 cGy over 20 min (900 cGy/20 min), one each with a Triangle and V-shaped dose pattern. WiDr cells were subjected to the same experiments with first 180 cGy/20 min, then 900 cGy/5 min. Cell survival was assessed using the clonogenic assay.
At 900 cGy/20 min, irradiation with a V-shaped pattern resulted in an increased survival compared with use of a Triangle pattern of 21.2% for WiDr (p < 0.01), 18.6% for PC-3 (p < 0.025), and 4.7% for SQ-20B cells (p > 0.05). For WiDr cells at 180 cGy/20 min, this increase reduced to 2.7% (p > 0.05) and to -0.8% (p > 0.05) at 900 cGy/5 min.
These results verify the assertions of the modeling study in vitro, and imply that the temporal pattern of applied dose should be considered in treatment planning and delivery.
通过实验验证在单次放射治疗中，应用剂量模式的时间调整如何影响细胞存活。
使用线性二次模型，我们先前已经证明，细胞存活的最大差异源于将在分次治疗中间给予最高剂量而在开始和结束时给予最低剂量的时间剂量模式（“三角形”）与在中间给予最低剂量而在开始和结束时给予最高剂量的模式（“V形”）进行比较。此外，在低α/β、大剂量/分次和分次长度的情况下，这些差异将最为显著。将两种低α/β（WiDr、PC-3）和一种高α/β（SQ-20B）细胞系在六孔板中于20分钟内照射900 cGy（900 cGy/20分钟），每种细胞系分别采用三角形和V形剂量模式。WiDr细胞先以180 cGy/20分钟，然后以900 cGy/5分钟进行相同实验。使用克隆形成试验评估细胞存活。
在900 cGy/20分钟时，与三角形模式相比，V形模式照射使WiDr细胞的存活率提高了21.2%（p < 0.01），PC-3细胞提高了18.6%（p < 0.025），SQ-20B细胞提高了4.7%（p > 0.05）。对于WiDr细胞，在180 cGy/20分钟时，这种提高降至2.7%（p > 0.05），在900 cGy/5分钟时降至 -0.8%（p > 0.05）。
这些结果验证了体外建模研究的论断，并表明在治疗计划和实施中应考虑应用剂量的时间模式。
