Witte Marnix, Pos Floris, Incrocci Luca, Heemsbergen Wilma
Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Department of Radiation Oncology, Erasmus Medical Center, Rotterdam, The Netherlands.
Phys Imaging Radiat Oncol. 2021 Jan 5;17:25-31. doi: 10.1016/j.phro.2020.12.003. eCollection 2021 Jan.
External beam radiotherapy for prostate cancer deposits incidental dose to a region surrounding the target volume. Previously, an association was identified between tumor control and incidental dose for patients treated with conventional radiotherapy. We investigated whether such an association exists for patients treated using intensity modulated radiotherapy (IMRT) and tighter margins.
Computed tomography scans and three-dimensional treatment planning dose distributions were available from the Dutch randomized HYPRO trial for 397 patients in the standard fractionation arm (39 × 2 Gy) and 407 patients in the hypofractionation arm (19 × 3.4 Gy), mainly delivered using online image-guided IMRT. Endpoint was any treatment failure within 5 years. A mapping of 3D dose distributions between anatomies was performed based on distance to the surface of the prostate delineation. Mean mapped dose distributions were computed for patient groups with and without failure, obtaining dose difference distributions. Random patient permutations were performed to derive p values and to identify relevant regions.
For high-risk patients treated in the conventional arm, higher incidental dose was significantly associated with a higher probability of tumor control in both univariate and multivariate analysis. The locations of the excess dose mainly overlapped with the position of obturator internus muscles at about 2.5 cm from the prostate surface. No such relationship could be established for intermediate-risk patients.
An association was established between reduced treatment failure and the delivery of incidental dose outside the prostate for high-risk patients treated using conventionally fractionated IMRT.
前列腺癌的外照射放疗会在靶区周围区域产生附带剂量。此前，已确定接受传统放疗的患者的肿瘤控制与附带剂量之间存在关联。我们研究了对于接受调强放疗（IMRT）和更窄边界的患者，是否存在这样的关联。
荷兰随机HYPRO试验提供了397例标准分割组（39×2 Gy）和407例大分割组（19×3.4 Gy）患者的计算机断层扫描和三维治疗计划剂量分布，主要采用在线图像引导IMRT。终点为5年内的任何治疗失败。基于到前列腺轮廓表面的距离，对不同解剖结构之间的三维剂量分布进行映射。计算有治疗失败和无治疗失败患者组的平均映射剂量分布，得到剂量差异分布。进行随机患者置换以得出p值并确定相关区域。
在传统治疗组中接受治疗的高危患者，在单变量和多变量分析中，较高的附带剂量均与较高的肿瘤控制概率显著相关。过量剂量的位置主要与距前列腺表面约2.5 cm处的闭孔内肌位置重叠。对于中危患者，未发现这种关系。
对于接受常规分割IMRT治疗的高危患者，治疗失败的减少与前列腺外附带剂量的给予之间存在关联。
