Sanguineti Giuseppe, Faiella Adriana, Farneti Alessia, D'Urso Pasqualina, Fuga Valentina, Olivieri Michela, Giannarelli Diana, Marzi Simona, Iaccarino Giuseppe, Landoni Valeria
Departments of Radiation Oncology, IRCCS Regina Elena National Cancer Institute, Rome, Italy.
Departments of Statistics, IRCCS Regina Elena National Cancer Institute, Rome, Italy.
Clin Transl Radiat Oncol. 2020 Jan 31;21:91-97. doi: 10.1016/j.ctro.2020.01.006. eCollection 2020 Mar.
Dose-volume objectives for the rectum have been proposed to limit long term toxicity after moderately hypofractionated radiotherapy (MHRT) for localized prostate cancer. The purpose of the present study is to validate and possibly refine dose volume objective for the rectal wall after 20-fraction MHRT.
All patients treated by 20-fraction MHRT at a single Institution were identified and relative rectal wall (%RW) DVH retrieved. The endpoint of the study is the development of grade 2+ late rectal bleeding (LRB) according to a modified RTOG scale. Clinical and dosimetric predictors of LRB were investigated at both uni- and multi-variable analysis.
293 patients were identified and analyzed. Of them, 35 (12%) developed the endpoint. At univariable analysis, antithrombotic drug usage (yes vs no), technique (3DCRT vs IMRT/VMAT) and several %RW DVH cut-points were significantly correlated with LRB. However, within patients treated by 3DCRT (N = 106), a bi-variable model including anti-thrombotic drug usage and selected %RW dose/volume metrics failed to identify independent dosimetric predictors of LRB. Conversely, within patients treated with intensity modulation (N = 187), the same model showed a progressively higher impact of the percent of RW receiving doses above 40 Gy. Based on this model, we were able to confirm (V32), refine (V60) and identify a novel (V50) cut-point for the %RW.
We recommend the following dose volume objectives for the %RW in order to minimize the risk of LRB after 20-fraction MHRT: V32 ≤ 50%; V50 ≤ 25.8% and V60 ≤ 10%.
已经提出了直肠的剂量 - 体积目标，以限制局部前列腺癌中度低分割放疗（MHRT）后的长期毒性。本研究的目的是验证并可能优化20次分割MHRT后直肠壁的剂量 - 体积目标。
确定了在单一机构接受20次分割MHRT治疗的所有患者，并检索了相对直肠壁（%RW）剂量体积直方图（DVH）。研究终点是根据改良的RTOG量表出现2级及以上晚期直肠出血（LRB）。在单变量和多变量分析中研究了LRB的临床和剂量学预测因素。
共确定并分析了293例患者。其中，35例（12%）出现了研究终点。在单变量分析中，抗血栓药物使用情况（是与否）、技术（3DCRT与IMRT/VMAT）以及几个%RW DVH切点与LRB显著相关。然而，在接受3DCRT治疗的患者（N = 106）中，一个包括抗血栓药物使用情况和选定的%RW剂量/体积指标的双变量模型未能识别出LRB的独立剂量学预测因素。相反，在接受调强放疗的患者（N = 187）中，相同的模型显示接受40 Gy以上剂量的RW百分比的影响逐渐增加。基于该模型，我们能够确认（V32）、优化（V60）并确定一个新的（V50）%RW切点。
为了将20次分割MHRT后LRB的风险降至最低，我们建议%RW的剂量 - 体积目标如下：V32≤50%；V50≤25.8%且V60≤10%。
