Roels Sarah, Slagmolen Pieter, Nuyts Johan, Lee John A, Loeckx Dirk, Maes Frederik, Stroobants Sigrid, Penninckx Freddy, Haustermans Karin
Leuven Cancer Institute, Radiation Oncology, University Hospital Leuven, Leuven, Belgium.
Acta Oncol. 2008;47(7):1237-48. doi: 10.1080/02841860802256434.
The purpose of this study is to investigate the use of PET/CT with fluorodeoxyglucose (FDG), fluorothymidine (FLT) and fluoromisonidazole (FMISO) for radiotherapy (RT) target definition and evolution in rectal cancer.
PET/CT was performed before and during preoperative chemoradiotherapy (CRT) in 15 patients with resectable rectal cancer. PET signals were delineated and CT images on the different time points were non-rigidly registered. Mismatch analyses were carried out to quantify the overlap between FDG and FLT or FMISO tumour volumes (TV) and between PET TVs over time.
Ninety sequential PET/CT images were analyzed. The mean FDG, FLT and FMISO-PET TVs showed a tendency to shrink during preoperative CRT. On each time point, the mean FDG-PET TV was significantly larger than the FMISO-PET TV but not significantly larger than the mean FLT-PET TV. There was a mean 65% mismatch between the FMISO and FDG TVs obtained before and during CRT. FLT TVs corresponded better with the FDG TVs (25% mismatch before and 56% during CRT). During CRT, on average 61% of the mean FDG TV (7 cc) overlapped with the baseline mean TV (15.5 cc) (n=15). For FLT, the TV overlap was 49% (n=5) and for FMISO only 20% of the TV during CRT remained inside the contour at baseline (n=10).
FDG, FLT and FMISO-PET reflect different functional characteristics that change during CRT in rectal cancer. FLT and FDG show good spatial correspondence, while FMISO seems less reliable due to the non-specific FMISO uptake in normoxic tissue and tracer diffusion through the bowel wall. FDG and FLT-PET/CT imaging seem most appropriate to integrate in preoperative RT for rectal cancer.
本研究旨在探讨使用氟脱氧葡萄糖（FDG）、氟胸苷（FLT）和氟米索硝唑（FMISO）的PET/CT在直肠癌放疗（RT）靶区定义及演变中的应用。
对15例可切除直肠癌患者在术前同步放化疗（CRT）前及期间进行PET/CT检查。勾勒出PET信号，并对不同时间点的CT图像进行非刚性配准。进行不匹配分析以量化FDG与FLT或FMISO肿瘤体积（TV）之间以及PET TV随时间的重叠情况。
分析了90幅连续的PET/CT图像。术前CRT期间，平均FDG、FLT和FMISO-PET TV呈缩小趋势。在每个时间点，平均FDG-PET TV显著大于FMISO-PET TV，但不显著大于平均FLT-PET TV。CRT前和期间获得的FMISO与FDG TV之间平均存在65%的不匹配。FLT TV与FDG TV的对应性更好（CRT前为25%不匹配，CRT期间为56%）。在CRT期间，平均FDG TV（7 cc）的61%与基线平均TV（15.5 cc）重叠（n = 15）。对于FLT，TV重叠率为49%（n = 5），对于FMISO，CRT期间仅20%的TV仍在基线轮廓内（n = 10）。
FDG、FLT和FMISO-PET反映了直肠癌CRT期间不同的功能特征变化。FLT和FDG显示出良好的空间对应性，而由于FMISO在正常组织中的非特异性摄取以及示踪剂通过肠壁扩散，FMISO似乎不太可靠。FDG和FLT-PET/CT成像似乎最适合纳入直肠癌术前放疗。
