Department of Radiation Oncology, University of Colorado Denver, Aurora, Colorado, USA.
Int J Radiat Oncol Biol Phys. 2012 Aug 1;83(5):e613-8. doi: 10.1016/j.ijrobp.2012.02.008. Epub 2012 Apr 10.
To characterize changes in standardized uptake value (SUV) in positron emission tomography (PET) scans and determine the pace of normal tissue regeneration after stereotactic body radiation therapy (SBRT) for solid tumor liver metastases.
We reviewed records of patients with liver metastases treated with SBRT to ≥40 Gy in 3-5 fractions. Evaluable patients had pretreatment PET and ≥1 post-treatment PET. Each PET/CT scan was fused to the planning computed tomography (CT) scan. The maximum SUV (SUV(max)) for each lesion and the total liver volume were measured on each PET/CT scan. Maximum SUV levels before and after SBRT were recorded.
Twenty-seven patients with 35 treated liver lesions were studied. The median follow-up was 15.7 months (range, 1.5-38.4 mo), with 5 PET scans per patient (range, 2-14). Exponential decay curve fitting (r=0.97) showed that SUV(max) declined to a plateau of 3.1 for controlled lesions at 5 months after SBRT. The estimated SUV(max) decay half-time was 2.0 months. The SUV(max) in controlled lesions fluctuated up to 4.2 during follow-up and later declined; this level is close to 2 standard deviations above the mean normal liver SUV(max) (4.01). A failure cutoff of SUV(max) ≥6 is twice the calculated plateau SUV(max) of controlled lesions. Parenchymal liver volume decreased by 20% at 3-6 months and regenerated to a new baseline level approximately 10% below the pretreatment level at 12 months.
Maximum SUV decreases over the first months after SBRT to plateau at 3.1, similar to the median SUV(max) of normal livers. Transient moderate increases in SUV(max) may be observed after SBRT. We propose a cutoff SUV(max) ≥6, twice the baseline normal liver SUV(max), to score local failure by PET criteria. Post-SBRT values between 4 and 6 would be suspicious for local tumor persistence or recurrence. The volume of normal liver reached nadir 3-6 months after SBRT and regenerated within the next 6 months.
描述正电子发射断层扫描（PET）扫描中标准化摄取值（SUV）的变化，并确定立体定向体部放射治疗（SBRT）治疗肝转移瘤后正常组织再生的速度。
我们回顾了接受 SBRT 治疗的肝转移瘤患者的记录，SBRT 的剂量为 3-5 个分次，每个分次≥40Gy。可评估的患者在治疗前和治疗后均有 PET 检查。每次 PET/CT 扫描均与计划 CT 扫描融合。在每次 PET/CT 扫描上测量每个病变的最大 SUV（SUV(max)）和总肝体积。记录 SBRT 前后的最大 SUV 水平。
研究了 27 例 35 个接受治疗的肝病变患者。中位随访时间为 15.7 个月（范围，1.5-38.4mo），每个患者有 5 次 PET 扫描（范围，2-14 次）。指数衰减曲线拟合（r=0.97）显示，SBRT 后 5 个月，SUV(max) 降至 3.1，达到控制病变的平台水平。SUV(max) 的估计衰减半时间为 2.0 个月。在随访期间，控制病变的 SUV(max) 波动高达 4.2，随后下降；这一水平接近正常肝 SUV(max)平均值（4.01）的 2 个标准差以上。SUV(max)≥6 的失败截定点是控制病变平台 SUV(max)的两倍。在 3-6 个月时，实质肝体积减少 20%，并在 12 个月时再生至接近治疗前水平的新基线水平，降低约 10%。
SBRT 后最初几个月 SUV(max) 下降，至 3.1 时达到平台水平，与正常肝脏 SUV(max)的中位数相似。SBRT 后可能会观察到 SUV(max)的短暂中度升高。我们提出了 SUV(max)≥6 的截定点，即正常肝 SUV(max)基线的两倍，以根据 PET 标准对局部失败进行评分。SBRT 后 4-6 之间的值可能提示局部肿瘤持续存在或复发。正常肝的体积在 SBRT 后 3-6 个月达到最低点，并在接下来的 6 个月内再生。
