Iwate Medical University PET-Liniac Advanced Medical Center, Uchimaru 19-1, Morioka 020-8505, Japan.
Radiat Oncol. 2012 Jan 31;7:15. doi: 10.1186/1748-717X-7-15.
BACKGROUND & PURPOSE: Rectal toxicity is less common after 125I seed implant brachytherapy for prostate cancer, and intraoperative rectal dose-volume constraints (the constraint) is still undetermined in pioneering studies. As our constraint failed to prevent grade 2 or 3 rectal bleeding (bled-pts) in 5.1% of patients, we retrospectively explored another constraint for the prevention of rectal bleeding.
The study population consisted of 197 patients treated with the brachytherapy as monotherapy using real-time intraoperative transrectal ultrasound (US)-guided treatment at a prescribed dose of 145 Gy. Post-implant dosimetry was performed on Day 1 and Day 30 after implantation using computed tomography (CT) imaging. Rectal bleeding toxicity was classified by CTC-AE ver. 3.0 during a mean 29-month (range, 12-48 months) period after implantation. The differences in rV100s were compared among intraoperative, Day 1 and Day 30 dosimetry, and between that of patients with grade 2 or 3 rectal bleeding (the bled-pts) and of the others (the spared-pts). All patients were divided into groups based on provisional rV100s that were increased stepwise in 0.1-cc increments from 0 to 1.0 cc. The difference in the ratios of the bled-pts to the spared-pts was tested by chi-square tests, and their odds ratios were calculated (bled-OR). All statistical analyses were performed by t-tests.
The mean values of rV100us, rV100CT_1, and rV100CT_30 were 0.31 ± 0.43, 0.22 ± 0.36, and 0.59 ± 0.68 cc, respectively. These values temporarily decreased (p = 0.020) on Day 1 and increased (p = 0.000) on Day 30. There was no significant difference in rV100s between the bled-pts and spared-pts at any time of dosimetry. The maximum bled-OR was identified among patients with an rV100us value above 0.1 cc (p = 0.025; OR = 7.8; 95% CI, 1.4-145.8); an rV100CT_1 value above 0.3 cc (p = 0.014; OR = 16.2; 95% CI, 3.9-110.7), and an rV100CT_30 value above 0.5 cc (p = 0.019; OR = 6.3; 95% CI, 1.5-42.3).
By retrospective analysis exploring rV100 as intraoperative rectal dose-volume thresholds in 125I seed implant brachytherapy for prostate cancer, it is proved that rV100 should be less than 0.1 cc for preventing rectal bleeding.
在前列腺癌 125I 种子植入近距离放射治疗后，直肠毒性较不常见，且在开拓性研究中，术中直肠剂量-体积限制（限制）仍未确定。由于我们的限制未能预防 5.1%的患者出现 2 或 3 级直肠出血（出血患者），我们回顾性地探索了另一种限制以预防直肠出血。
研究人群由 197 名接受 145 Gy 规定剂量的实时术中经直肠超声（US）引导治疗的单纯近距离放射治疗的患者组成。植入后第 1 天和第 30 天使用计算机断层扫描（CT）成像进行植入后剂量测定。在植入后平均 29 个月（范围 12-48 个月）期间，使用 CTC-AE ver. 3.0 对直肠出血毒性进行分类。比较术中、第 1 天和第 30 天剂量测定的 rV100s 差异，以及 2 或 3 级直肠出血（出血患者）和其他患者（未出血患者）的 rV100s 差异。所有患者均根据 rV100s 进行分组，该值以 0.1cc 为增量从 0 递增至 1.0cc。通过卡方检验检验出血患者与未出血患者之间出血比的差异，并计算其比值比（bled-OR）。所有统计分析均通过 t 检验进行。
rV100us、rV100CT_1 和 rV100CT_30 的平均值分别为 0.31±0.43、0.22±0.36 和 0.59±0.68cc。这些值在第 1 天暂时降低（p=0.020），在第 30 天增加（p=0.000）。在任何剂量测定时间，出血患者与未出血患者的 rV100s 均无显著差异。在 rV100us 值大于 0.1cc（p=0.025；OR=7.8；95%CI，1.4-145.8）、rV100CT_1 值大于 0.3cc（p=0.014；OR=16.2；95%CI，3.9-110.7）和 rV100CT_30 值大于 0.5cc（p=0.019；OR=6.3；95%CI，1.5-42.3）的患者中，最大的出血比值比（bled-OR）被识别出来。
通过对前列腺癌 125I 种子植入近距离放射治疗中 rV100 作为术中直肠剂量-体积阈值的回顾性分析，证明 rV100 应小于 0.1cc 以预防直肠出血。
