Whaley Jonathan T, Fernandes Annemarie T, Sackmann Robert, Plastaras John P, Teo Boon-Keng, Grover Surbhi, Perini Rodolfo F, Metz James M, Pryma Daniel A, Apisarnthanarax Smith
Department of Radiation Oncology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
Division of Nuclear Medicine, Department of Radiology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
Pract Radiat Oncol. 2014 Jul-Aug;4(4):226-32. doi: 10.1016/j.prro.2013.09.002. Epub 2013 Oct 22.
The role of 18F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) in the staging and radiation treatment planning of locally advanced rectal cancer is ill defined. We studied the role of integrated PET/CT in the staging, radiation treatment planning, and use as an imaging biomarker in rectal cancer patients undergoing multimodality treatment.
Thirty-four consecutive patients with T3-4N0-2M0-1 rectal adenocarcinoma underwent FDG-PET/CT scanning for staging and radiation treatment planning. Planned clinical management was compared before and after the addition of PET/CT information. Three radiation oncologists independently delineated CT-based gross tumor volumes (GTVCT) using clinical information and CT imaging data, as well as gradient autosegmented PET/CT-based GTVs (GTVPETCT). The mean GTV, interobserver concordance index (CCI), and proximal and distal margins were compared. The maximal standardized uptake value (SUVmax), metabolic tumor volume (MTV), and dual-time point PET parameters were correlated with clinicopathologic endpoints.
Clinical management was altered by PET/CT in 18% (n = 6) of patients with clinical upstaging in 6 patients and radiation treatment planning altered in 5 patients. Of the 30 evaluable preoperative patients, the mean GTVPETCT was significantly smaller than the mean GTVCT volumes: 88.1 versus 102.8 cc (P = .03). PET/CT significantly increased interobserver CCI in contouring GTV compared with CT only-based contouring: 0.56 versus 0.38 (P < .001). The proximal and distal margins were altered by a mean of 0.4 ± 0.24 cm and -0.25 ± 0.18 cm, respectively. MTV was inversely associated with 2-year progression-free survival (PFS) and overall survival (OS): smaller MTVs (<33 cc) had superior 2-year PFS (86% vs 60%, P = .04) and OS (100% vs 45%, P < .01) compared with larger MTVs (>33 cc). SUVmax and dual-time point PET parameters did not correlate with any endpoints.
FDG-PET/CT imaging impacts overall clinical management and is useful in the radiation treatment planning of rectal cancer patients by decreasing interobserver variability in contouring target boost volumes. Pretreatment MTV may provide useful prognostic information and requires further study.
18F-氟脱氧葡萄糖正电子发射断层扫描-计算机断层扫描（FDG-PET/CT）在局部晚期直肠癌分期及放射治疗计划中的作用尚不明确。我们研究了PET/CT融合成像在接受多模式治疗的直肠癌患者的分期、放射治疗计划制定以及作为影像生物标志物方面的作用。
34例连续的T3-4N0-2M0-1直肠腺癌患者接受FDG-PET/CT扫描以进行分期和放射治疗计划制定。在加入PET/CT信息前后比较计划的临床管理。三位放射肿瘤学家分别使用临床信息和CT影像数据勾勒基于CT的大体肿瘤体积（GTVCT），以及基于PET/CT梯度自动分割的GTV（GTVPETCT）。比较平均GTV、观察者间一致性指数（CCI）以及近端和远端边界。将最大标准化摄取值（SUVmax）、代谢肿瘤体积（MTV）和双时相PET参数与临床病理终点进行相关性分析。
PET/CT使18%（n = 6）的患者临床分期发生改变，其中6例患者临床分期上调，5例患者放射治疗计划改变。在30例可评估的术前患者中，平均GTVPETCT显著小于平均GTVCT体积：88.1 vs 102.8 cc（P = 0.03）。与仅基于CT的轮廓勾画相比，PET/CT在勾画GTV时显著提高了观察者间CCI：0.56 vs 0.38（P < 0.001）。近端和远端边界平均分别改变了0.4 ± 0.24 cm和 -0.25 ± 0.18 cm。MTV与2年无进展生存期（PFS）和总生存期（OS）呈负相关：与较大MTV（>33 cc）相比，较小MTV（<33 cc）的患者2年PFS更佳（86% vs 60%，P = 0.04），OS也更佳（100% vs 45%，P < 0.01）。SUVmax和双时相PET参数与任何终点均无相关性。
FDG-PET/CT成像影响整体临床管理，通过减少勾画靶区增强体积时观察者间的变异性，对直肠癌患者的放射治疗计划制定有用。治疗前MTV可能提供有用的预后信息，需要进一步研究。
