Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI 48073, USA.
Int J Radiat Oncol Biol Phys. 2012 Jul 1;83(3):947-52. doi: 10.1016/j.ijrobp.2011.08.025. Epub 2011 Dec 28.
Rectal distension has been shown to decrease the probability of biochemical control. Adaptive image-guided radiotherapy (IGRT) corrects for target position and volume variations, reducing the risk of biochemical failure while yielding acceptable rates of gastrointestinal (GI)/genitourinary (GU) toxicities.
Between 1998 and 2006, 962 patients were treated with computed tomography (CT)-based offline adaptive IGRT. Patients were stratified into low (n = 400) vs. intermediate/high (n = 562) National Comprehensive Cancer Network (NCCN) risk groups. Target motion was assessed with daily CT during the first week. Electronic portal imaging device (EPID) was used to measure daily setup error. Patient-specific confidence-limited planning target volumes (cl-PTV) were then constructed, reducing the standard PTV and compensating for geometric variation of the target and setup errors. Rectal volume (RV), cross-sectional area (CSA), and rectal volume from the seminal vesicles to the inferior prostate (SVP) were assessed on the planning CT. The impact of these volumetric parameters on 5-year biochemical control (BC) and chronic Grades ≥2 and 3 GU and GI toxicity were examined.
Median follow-up was 5.5 years. Median minimum dose covering cl-PTV was 75.6 Gy. Median values for RV, CSA, and SVP were 82.8 cm(3), 5.6 cm(2), and 53.3 cm(3), respectively. The 5-year BC was 89% for the entire group: 96% for low risk and 83% for intermediate/high risk (p < 0.001). No statistically significant differences in BC were seen with stratification by RV, CSA, and SVP in quartiles. Maximum chronic Grades ≥2 and 3 GI toxicities were 21.2% and 2.9%, respectively. Respective values for GU toxicities were 15.5% and 4.3%. No differences in GI or GU toxicities were noted when patients were stratified by RV.
Incorporation of adaptive IGRT reduces the risk of geometric miss and results in excellent biochemical control that is independent of rectal volume/distension while maintaining very low rates of chronic GI toxicity.
直肠扩张已被证明会降低生化控制的概率。自适应图像引导放疗（IGRT）可纠正靶区位置和体积的变化，降低生化失败的风险，同时产生可接受的胃肠道（GI）/泌尿生殖系统（GU）毒性发生率。
1998 年至 2006 年间，962 例患者接受了基于计算机断层扫描（CT）的离线自适应 IGRT 治疗。患者被分为低（n=400）和中/高（n=562）国家综合癌症网络（NCCN）风险组。在第一周内每天进行 CT 评估靶区运动。电子射野影像装置（EPID）用于测量每日的摆位误差。然后构建了患者特异性的限定置信区间的计划靶区（cl-PTV），缩小了标准 PTV，并补偿了靶区和摆位误差的几何变化。在计划 CT 上评估直肠体积（RV）、横截面积（CSA）和从精囊到前列腺下部（SVP）的直肠体积。检查这些容积参数对 5 年生化控制（BC）和慢性 2 级和 3 级 GU 和 GI 毒性的影响。
中位随访时间为 5.5 年。cl-PTV 最小覆盖剂量的中位值为 75.6 Gy。RV、CSA 和 SVP 的中位值分别为 82.8 cm³、5.6 cm²和 53.3 cm³。整个组的 5 年 BC 为 89%：低危组为 96%，中高危组为 83%（p<0.001）。按 RV、CSA 和 SVP 四分位数分层，BC 无统计学差异。最大慢性 2 级和 3 级 GI 毒性分别为 21.2%和 2.9%。GU 毒性的相应值分别为 15.5%和 4.3%。按 RV 分层时，GI 或 GU 毒性无差异。
自适应 IGRT 的应用降低了几何误差的风险，生化控制效果极佳，与直肠容积/扩张无关，同时保持非常低的慢性 GI 毒性发生率。
