Department of Radiation Oncology, MAASTRO, GROW - School for Oncology and Developmental Biology, Maastricht University Medical Centre, The Netherlands.
Radiother Oncol. 2012 Mar;102(3):371-6. doi: 10.1016/j.radonc.2011.12.016. Epub 2012 Jan 24.
Previously, we showed a good correlation between pathology and an automatically generated PET-contour in rectal cancer. This study analyzed the effect of the use of PET-CT scan on the interobserver variation in GTV definition in rectal cancer and the influence of PET-CT on treatment volumes.
Forty two patients diagnosed with rectal cancer underwent an FDG-PET-CT for radiotherapy planning. An automatic contour was created on PET-scan using the source-to-background ratio. The GTV was delineated by 5 observers in 3 rounds: using CT and MRI, using CT, MRI and PET and using CT, MRI and PET auto-contour. GTV volumes were compared and concordance indices (CI) were calculated. Since the GTV is only a small portion of the treatment volume in rectal cancer, a separate analysis was performed to evaluate the influence of PET on the definition of the CTV used in daily clinical practice and the caudal extension of the treatment volumes.
GTV volumes based on PET were significantly smaller. CIs increased significantly using PET and the best interobserver agreement was observed using PET auto-contours. Furthermore, we found that in up to 29% of patients the CTV based on PET extended outside the CTV used in clinical practice. The caudal border of the treatment volume can be tailored using PET-scan in low seated tumors. Influence of PET on the position of the caudal border was most pronounced in high seated tumors.
PET-CT increases the interobserver agreement in the GTV definition in rectal cancer, helps to avoid geographical misses and allows tailoring the caudal border of the treatment volume.
此前，我们发现直肠癌的病理与自动生成的 PET 勾画之间具有良好的相关性。本研究分析了在直肠癌中使用 PET-CT 扫描对 GTV 勾画的观察者间变异性的影响，以及 PET-CT 对治疗体积的影响。
42 例诊断为直肠癌的患者接受了 FDG-PET-CT 放疗计划。使用源背景比在 PET 扫描上创建自动轮廓。5 位观察者在 3 轮中勾画 GTV：使用 CT 和 MRI、使用 CT、MRI 和 PET、使用 CT、MRI 和 PET 自动轮廓。比较 GTV 体积并计算一致性指数 (CI)。由于 GTV 仅是直肠癌治疗体积的一小部分，因此进行了单独的分析，以评估 PET 对日常临床实践中 CTV 定义以及治疗体积尾部延伸的影响。
基于 PET 的 GTV 体积明显较小。使用 PET 时，CI 显著增加，使用 PET 自动轮廓时观察到最佳的观察者间一致性。此外，我们发现高达 29%的患者的 CTV 基于 PET 延伸超出了临床实践中使用的 CTV。在低位直肠癌中，PET 扫描可用于调整治疗体积的尾部边界。PET 对尾部边界位置的影响在高位直肠癌中最为明显。
PET-CT 增加了直肠癌 GTV 定义的观察者间一致性，有助于避免地理漏诊，并允许调整治疗体积的尾部边界。
