Image-based treatment planning with FDG-PET/CT fusion in CyberKnife radiotherapy in patients with recurrent head and neck cancers

Abstract

1667

Objectives: Recently, CyberKnife irradiation system which is a compact x-band linear accelerator mounted on a robotic arm with 6-degrees of freedom has been developed. To obtain successful therapy with CyberKnife, outlining the target and critical structures and defining the treatment target are predominantly essentials and are associated primarily with the robot and imaging system. CT image and PET image have provided complementary information in treatment planning in radiotherapy. The aim of this study is to access the efficacy of image-based irradiation planning using FDG-PET image fused with CT image in patients with recurrent head and neck cancer.

Methods: Twenty patients (mean age: 59.0+/-10.9 y-o) with head and neck cancer underwent CT and FDG-PET examinations prior to CyberKnife irradiation therapy. CT image was acquired with IV contrast media. PET image was obtained 1 hour after injection of 185 MBq of F-18 FDG with PET camera. Both images were obtained within a week with the same posture as CyberKnife therapy and were analyzed for fusion-image on a workstation. For treatment planning with CyberKnife, the gross tumor volume (GTV) was defined by CT and FDG-PET/CT image fusion, respectively. After decision of each GTV with an agreement of nuclear medicine physicians and radiation oncologists, CyberKnife radiotherapy was performed. Patients were evaluated in follow-up by clinical investigators and MRI, CT, FDG-PET or a surgical examination to confirm histopathological diagnosis after irradiation.

Results: All patients had a series of three to eight-fractionated of CyberKnife irradiation with total dose of 35 Gy in average. The tumor dose was maintained at 24 to 35 Gy to the 80% isodose line. In decision of GTV, 15 of 20 (75%) patients did not significantly differ between methods using CT image and PET/CT fused image. However, 10 % (2/20) were decreased in GTV with PET/CT fusion and 15 % (3/20) were also increased. Mucositis such as nasopharingitis which is the most common acute side effects of irradiation was suppressed in 15 % (3/20) with grade 1 or 2. No significant sub-acute complications after irradiation were observed.

Conclusions: Image-based treatment planning with FDG-PET/CT fusion in CyberKnife radiotherapy plays a major role in the definition of accurate tumor extent and allows successful and sufficient treatment with recurrent head and neck cancers.