School of Chemistry and Physics, The University of Adelaide, Adelaide, SA 5000, Australia.
Med Phys. 2010 Sep;37(9):5126-37. doi: 10.1118/1.3481514.
Normal tissue complication probability (NTCP) of the rectum, bladder, urethra, and femoral heads following several techniques for radiation treatment of prostate cancer were evaluated applying the relative seriality and Lyman models.
Model parameters from literature were used in this evaluation. The treatment techniques included external (standard fractionated, hypofractionated, and dose-escalated) three-dimensional conformal radiotherapy (3D-CRT), low-dose-rate (LDR) brachytherapy (I-125 seeds), and high-dose-rate (HDR) brachytherapy (Ir-192 source). Dose-volume histograms (DVHs) of the rectum, bladder, and urethra retrieved from corresponding treatment planning systems were converted to biological effective dose-based and equivalent dose-based DVHs, respectively, in order to account for differences in radiation treatment modality and fractionation schedule.
Results indicated that with hypofractionated 3D-CRT (20 fractions of 2.75 Gy/fraction delivered five times/week to total dose of 55 Gy), NTCP of the rectum, bladder, and urethra were less than those for standard fractionated 3D-CRT using a four-field technique (32 fractions of 2 Gy/fraction delivered five times/week to total dose of 64 Gy) and dose-escalated 3D-CRT. Rectal and bladder NTCPs (5.2% and 6.6%, respectively) following the dose-escalated four-field 3D-CRT (2 Gy/fraction to total dose of 74 Gy) were the highest among analyzed treatment techniques. The average NTCP for the rectum and urethra were 0.6% and 24.7% for LDR-BT and 0.5% and 11.2% for HDR-BT.
Although brachytherapy techniques resulted in delivering larger equivalent doses to normal tissues, the corresponding NTCPs were lower than those of external beam techniques other than the urethra because of much smaller volumes irradiated to higher doses. Among analyzed normal tissues, the femoral heads were found to have the lowest probability of complications as most of their volume was irradiated to lower equivalent doses compared to other tissues.
采用相对序列和 Lyman 模型评估前列腺癌放射治疗的几种技术对直肠、膀胱、尿道和股骨头的正常组织并发症概率（NTCP）。
本研究评估中使用了文献中的模型参数。治疗技术包括外部（标准分割、低分割和剂量递增）三维适形放疗（3D-CRT）、低剂量率（LDR）近距离放射治疗（I-125 种子）和高剂量率（HDR）近距离放射治疗（Ir-192 源）。从相应的治疗计划系统中检索到的直肠、膀胱和尿道的剂量-体积直方图（DVH）分别转换为基于生物有效剂量和等效剂量的 DVH，以考虑放射治疗方式和分割方案的差异。
结果表明，与标准分割的 3D-CRT（2.75 Gy/分次，每周 5 次，总剂量 55 Gy）相比，20 次 2.75 Gy/分次，每周 5 次，总剂量 55 Gy 的低分割 3D-CRT 的直肠、膀胱和尿道的 NTCP 较低，且剂量递增 3D-CRT 较低。剂量递增的四野 3D-CRT（2 Gy/分次，总剂量 74 Gy）后的直肠和膀胱 NTCP（分别为 5.2%和 6.6%）在分析的治疗技术中最高。LDR-BT 的直肠和尿道平均 NTCP 分别为 0.6%和 24.7%，HDR-BT 的直肠和尿道平均 NTCP 分别为 0.5%和 11.2%。
尽管近距离放射治疗技术会导致正常组织接受更大的等效剂量，但由于照射到更高剂量的体积较小，相应的 NTCP 低于外部束技术（除了尿道）。在分析的正常组织中，股骨头的并发症概率最低，因为与其他组织相比，其大部分体积接受的等效剂量较低。
