Schnell E, De La Fuente Herman T, Algan O, Syzek L, Herman T, Young J, Hildebrand K, Ahmad S
Oklahoma UniversityHealth Science Ctr., Oklahoma City, OK.
Med Phys. 2012 Jun;39(6Part19):3838. doi: 10.1118/1.4735666.
This study aims to evaluate treatment plans generated by Step- and-Shoot (SS), Sliding Window (SW) and Volumetric Modulated Arc Therapy (VMAT) in order to assess the differences in dose volume histograms of planning target volume (PTV) and organs at risk (OAR), conformity indices, radiobiological evaluations, and plan quality for prostate cancer cases.
Six prostate cancer patients treated in our center were selected for this retrospective study. Treatment plans were generated with Eclipse version 8.9 using 10 MV photon beams. For VMAT, Varian Rapid Arc with 1 or 2 arcs, and for SS and SW IMRT, 7-9 fields were used. Each plan had three PTVs with prescription doses of 81, 59.4, and 45 Gy to prostate, to prostate and lymph nodes, and to pelvis, respectively. Doses to PTV and OAR and the conformal indices (COIN) were compared among three techniques. The equivalent uniform dose (EUD), tumor control probability (TCP) and normal tissue complication probability (NTCP) was also calculated and compared.
The mean doses to the PTV prostate on average were 83 Gy and the percent differences of mean dose among all techniques were below 0.28. For bladder and rectum, the percent differences of mean dose among all techniques were below 2.2. The COIN did not favour any particular delivery method over the other. The TCP was higher with SS and SW for four patients and higher with VMAT for two patients. The NTCP for the rectum was the lowest with VMAT in all patients except one.
Preliminary data shows similar target coverage in general. We will extend our study to include 15 patients to compare different approaches with statistics. We will attempt to define characteristics predictive of the superior delivery technique.
本研究旨在评估步进式调强放疗（SS）、滑动窗口调强放疗（SW）和容积调强弧形放疗（VMAT）生成的治疗计划，以评估前列腺癌病例中计划靶区（PTV）和危及器官（OAR）的剂量体积直方图差异、适形指数、放射生物学评估和计划质量。
本回顾性研究选取了在本中心接受治疗的6例前列腺癌患者。使用Eclipse 8.9版本，采用10 MV光子束生成治疗计划。对于VMAT，使用1或2个弧形的Varian Rapid Arc；对于SS和SW调强放疗，使用7 - 9个射野。每个计划有三个PTV，前列腺、前列腺及淋巴结、骨盆的处方剂量分别为81 Gy、59.4 Gy和45 Gy。比较三种技术对PTV和OAR的剂量以及适形指数（COIN）。还计算并比较了等效均匀剂量（EUD）、肿瘤控制概率（TCP）和正常组织并发症概率（NTCP）。
PTV前列腺的平均剂量平均为83 Gy，所有技术之间平均剂量的百分比差异低于0.28。对于膀胱和直肠，所有技术之间平均剂量的百分比差异低于2.2。COIN并不倾向于任何一种特定的放疗方式。4例患者的TCP在SS和SW技术下较高，2例患者在VMAT技术下较高。除1例患者外，所有患者直肠的NTCP在VMAT技术下最低。
初步数据总体显示靶区覆盖情况相似。我们将扩大研究范围至纳入15例患者，以便通过统计学方法比较不同方法。我们将尝试确定能够预测更优放疗技术的特征。
