Alexander S E, McNair H A, Oelfke U, Huddart R, Murray J, Pathmanathan A, Patel P, Sritharan K, van As N, Tree A C
The Royal Marsden NHS Foundation Trust, Sutton, UK; The Institute of Cancer Research, London, UK.
The Royal Marsden NHS Foundation Trust, Sutton, UK; The Institute of Cancer Research, London, UK.
Clin Oncol (R Coll Radiol). 2022 Sep;34(9):e383-e391. doi: 10.1016/j.clon.2022.03.022. Epub 2022 Apr 22.
Prostate morphological changes during external beam radiotherapy are poorly understood. Excellent soft-tissue visualisation offered by magnetic resonance image-guided radiotherapy (MRIgRT) provides an opportunity to better understand such changes. The aim of this study was to quantify prostate volume and dimension changes occurring during extreme and moderately hypofractionated schedules.
Forty prostate cancer patients treated on the Unity 1.5 Tesla magnetic resonance linear accelerator (MRL) were retrospectively reviewed. The cohort comprised patients treated with 36.25 Gy in five fractions (n = 20) and 60 Gy in 20 fractions (n = 20). The volume of the delineated prostates on reference planning computed tomography (fused with MRI) and daily T2-weighted 2-min session images acquired on Unity were charted. Forty planning computed tomography and 500 MRL prostate volumes were evaluated. The mean absolute and relative change in prostate volume during radiotherapy was compared using a paired t-test (P value <0.01 considered significant to control for multiple comparisons). The maximum dimension of the delineated prostate was measured in three isocentric planes.
Significant prostate volume changes, relative to MRL imaging fraction 1 (MRL#1), were seen at all time points for the five-fraction group. The peak mean relative volume increase was 21% (P < 0.001), occurring at MRL#3 and MRL#4 after 14.5 and 21.75 Gy, respectively. Prostate expansion was greatest in the superior-inferior direction; the peak mean maximal extension was 5.9 mm. The maximal extension in the left-right and anterior-posterior directions measured 1.1 and 2.2 mm, respectively. For the 20-fraction group, prostate volume increased relative to MRL#1, for all treatment time points. The mean relative volume increase was 11% (P < 0.001) at MRL#5 after 12 Gy, it then fluctuated between 8 and 13%. From MRL#5 to MRL#20, the volume increase was significant (P < 0.01) for 12 of 16 time points calculated. The peak mean maximal extension in the superior-inferior direction was 3.1 mm. The maximal extension in the left-right and anterior-posterior directions measured 1.7 and 3.7 mm, respectively.
Significant prostate volume and dimension changes occur during extreme and moderately hypofractionated radiotherapy. The extent of change was greater during extreme hypofractionation. MRIgRT offers the opportunity to reveal, quantify and correct for this deformation.
对于外照射放疗期间前列腺的形态变化了解甚少。磁共振图像引导放疗（MRIgRT）所提供的出色软组织可视化效果为更好地理解此类变化提供了契机。本研究的目的是量化在大分割和中等程度低分割放疗方案期间发生的前列腺体积和尺寸变化。
对在Unity 1.5特斯拉磁共振直线加速器（MRL）上接受治疗的40例前列腺癌患者进行回顾性研究。该队列包括接受5次分割共36.25 Gy照射的患者（n = 20）和接受20次分割共60 Gy照射的患者（n = 20）。绘制参考计划计算机断层扫描（与MRI融合）上勾画的前列腺体积以及在Unity上采集的每日2分钟T2加权图像上的前列腺体积。评估了40次计划计算机断层扫描和500个MRL前列腺体积。使用配对t检验比较放疗期间前列腺体积的平均绝对变化和相对变化（P值<0.01被认为具有统计学意义，以控制多重比较）。在三个等中心平面测量勾画前列腺的最大尺寸。
对于5次分割组，在所有时间点相对于MRL成像第1次（MRL#1）均观察到前列腺体积有显著变化。平均相对体积增加的峰值为21%（P < 0.001），分别在14.5 Gy和21.75 Gy后的MRL#3和MRL#4时出现。前列腺在上下方向的扩张最大；平均最大延伸峰值为5.9毫米。左右方向和前后方向的最大延伸分别为1.1毫米和2.2毫米。对于20次分割组，在所有治疗时间点前列腺体积相对于MRL#1均增加。在12 Gy后的MRL#5时平均相对体积增加为11%（P < 0.001），随后在8%至13%之间波动。从MRL#5到MRL#20，在计算的16个时间点中的12个时间点体积增加具有统计学意义（P < 0.01）。上下方向的平均最大延伸峰值为3.1毫米。左右方向和前后方向的最大延伸分别为1.7毫米和3.7毫米。
在大分割和中等程度低分割放疗期间发生显著的前列腺体积和尺寸变化。在大分割放疗期间变化程度更大。MRIgRT提供了揭示、量化和校正这种变形的机会。
