Department of Medical Physics, University of Wisconsin, Madison, Wisconsin, USA.
J Nucl Med. 2013 Aug;54(8):1188-94. doi: 10.2967/jnumed.112.113332. Epub 2013 Jun 17.
PET-based treatment response studies typically measure the change in the standardized uptake value (SUV) to quantify response. The relative changes of different SUV measures, such as maximum, peak, mean, or total SUVs (SUV(max), SUV(peak), SUV(mean), or SUV(total), respectively), are used across the literature to classify patients into response categories, with quantitative thresholds separating the different categories. We investigated the impact of different SUV measures on the quantification and classification of PET-based treatment response.
Sixteen patients with solid malignancies were treated with a multitargeted receptor tyrosine kinase inhibitor, resulting in a variety of responses. Using the cellular proliferation marker 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT), we acquired whole-body PET/CT scans at baseline, during treatment, and after treatment. The highest (18)F-FLT uptake lesions (~2/patient) were segmented on PET images. Tumor PET response was assessed via the relative change in SUV(max), SUV(peak), SUV(mean), and SUV(total), thereby yielding 4 different responses for each tumor at mid- and posttreatment. For each SUV measure, a population average PET response was determined over all tumors. Standard deviation (SD) and range were used to quantify variation of PET response within individual tumors and population averages.
Different SUV measures resulted in substantial variation of individual tumor PET response assessments (average SD, 20%; average range, 40%). The most extreme variation between 4 PET response measures was 90% in individual tumors. Classification of tumor PET response depended strongly on the SUV measure, because different SUV measures resulted in conflicting categorizations of PET response (ambiguous treatment response assessment) in more than 80% of tumors. Variation of the population average PET response was considerably smaller (average SD, 7%; average range, 16%), and this variation was not statistically significant. Differences in tumor PET response were greatest between SUV(mean) and SUV(total) and smallest between SUV(max) and SUV(peak). Variations of tumor PET response at midtreatment and posttreatment were similar.
Quantification and classification of PET-based treatment response in individual patients were strongly affected by the SUV measure used to assess response. This substantial uncertainty in individual patient PET response was present despite the concurrent robustness of the population average PET response. Given the ambiguity of individual patient PET responses, selection of PET-based treatment response measures and their associated thresholds should be carefully optimized.
探讨不同 SUV 测量值对基于 PET 的治疗反应定量和分类的影响。
16 例实体恶性肿瘤患者接受多靶点受体酪氨酸激酶抑制剂治疗，导致多种反应。使用细胞增殖标志物 3'-脱氧-3'-(18)F-氟胸苷（(18)F-FLT），我们在基线、治疗期间和治疗后采集全身 PET/CT 扫描。在 PET 图像上对摄取最高的（18)F-FLT 摄取病变（~2/例）进行分段。通过 SUV(max)、SUV(peak)、SUV(mean)和 SUV(total)的相对变化评估肿瘤的 PET 反应，从而在中晚期治疗时为每个肿瘤产生 4 种不同的反应。对于每个 SUV 测量值，通过对所有肿瘤的平均人群 PET 反应来确定。标准差（SD）和范围用于量化个体肿瘤和人群平均 PET 反应的变异性。
不同的 SUV 测量值导致个体肿瘤的 PET 反应评估存在显著差异（平均 SD，20%；平均范围，40%）。在个体肿瘤中，4 种 PET 反应测量值之间的差异最大为 90%。肿瘤 PET 反应的分类强烈依赖于 SUV 测量值，因为不同的 SUV 测量值导致超过 80%的肿瘤 PET 反应存在分类冲突（治疗反应评估不明确）。人群平均 PET 反应的变异性要小得多（平均 SD，7%；平均范围，16%），且无统计学意义。SUV(mean)和 SUV(total)之间的肿瘤 PET 反应差异最大，SUV(max)和 SUV(peak)之间的差异最小。中期和后期肿瘤 PET 反应的变化相似。
个体患者基于 PET 的治疗反应的定量和分类受到用于评估反应的 SUV 测量值的强烈影响。尽管人群平均 PET 反应具有稳健性，但在个体患者的 PET 反应中存在这种显著的不确定性。鉴于个体患者的 PET 反应存在歧义，应仔细优化基于 PET 的治疗反应测量值及其相关阈值的选择。
