Hillbrand Martin, Georg Dietmar, Gadner Helmut, Pötter Richard, Dieckmann Karin
Department of Radiotherapy and Radiobiology, AKH Vienna, Medical University Vienna, Austria.
Radiother Oncol. 2008 Nov;89(2):141-9. doi: 10.1016/j.radonc.2008.06.012. Epub 2008 Aug 8.
Evaluation of dosimetric benefits of advanced radiotherapy techniques for the treatment of abdominal lesions during early childhood.
Treatment planning was performed for five Neuroblastoma (NBL) and four Wilms Tumor (WT) patients. Opposing fields (2F), photon intensity modulated radiotherapy (IMXT) and two proton techniques (passively scattered (PT) and scanned beams (IMPT)) were considered. Averaged dose-volume histograms, associated dosimetric parameters and a radiobiological model for the estimation of the therapy related carcinogenic effect were evaluated.
With respect to the 2F technique, both proton techniques enabled to reduce mean liver and kidney dose by 40-60%; Organ fractions irradiated at the level of the tolerance dose were reduced by 65% for kidneys and 75% for the liver in NBL patients and by additional 10% for WT patients. IMXT enabled to reduce parameters related to the steep high-dose gradient, e.g., V(15Gy) for the kidneys was reduced by a factor 2-3 compared to 2F. V(12Gy) was reduced by 40% in the liver. On the other side, the improvement of those parameters characterizing the low isodose domain was limited for IMXT. The risk for radiation-induced secondary cancer was doubled for IMXT and even more increased for PT if secondary neutrons were taken into account, while this risk remained the same or was reduced by IMPT with respect to 2F.
Proton beams improved all dosimetric parameters for NBL and WT patients compared to photon techniques. This improvement was limited for IMXT mainly to parameters related to the steep high-dose gradient. Further research is needed to minimize uncertainties for secondary cancer estimations.
评估先进放疗技术对幼儿腹部病变治疗的剂量学益处。
对5例神经母细胞瘤（NBL）和4例肾母细胞瘤（WT）患者进行治疗计划。考虑了对穿野（2F）、光子调强放疗（IMXT）和两种质子技术（被动散射（PT）和扫描束（IMPT））。评估了平均剂量体积直方图、相关剂量学参数以及用于估计治疗相关致癌效应的放射生物学模型。
与2F技术相比，两种质子技术均能使肝脏和肾脏的平均剂量降低40%-60%；在NBL患者中，肾脏和肝脏在耐受剂量水平下的受照器官体积分别减少65%和75%，WT患者在此基础上再减少10%。IMXT能够降低与陡峭高剂量梯度相关的参数，例如，与2F相比，肾脏的V(15Gy)降低了2-3倍。肝脏的V(12Gy)降低了40%。另一方面，IMXT在表征低剂量域的参数改善方面较为有限。如果考虑次级中子，IMXT的辐射诱发继发性癌症风险增加了一倍，PT的风险增加得更多，而与2F相比，IMPT的这种风险保持不变或降低。
与光子技术相比，质子束改善了NBL和WT患者的所有剂量学参数。IMXT的这种改善主要局限于与陡峭高剂量梯度相关的参数。需要进一步研究以尽量减少继发性癌症估计的不确定性。
