The influence of Radiotherapy on FDG-uptake.

Zwol, J.G. van (2014) The influence of Radiotherapy on FDG-uptake. thesis, Medicine.

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Abstract

The purpose of this retrospective study was to evaluate if FDG-uptake (a glucose tracer analog [18F]2-deoxy-2-fluoro-D-glucose (18F-FDG)) used in positron emission tomography (PET) is influenced by the received dose of radiotherapy 3, 6, 9 and 12 months after treatment in patients with a squamous cell carcinoma of the oral cavity or oropharynx (OOSCC). Methods and Materials: In this retrospective study patients without a recurrence in the two years after being treated and who underwent radiotherapy were selected from the FOOCAP (Follow-up of Oral and Oropharyngeal Cancer by PET) study. All these patients had been treated curatively for an advanced (stage III and IV) OOSCC and underwent serial 18F-FDG-PET investigations at 3, 6, 9, and 12 months after treatment. To analyze if radiotherapy influences FDG-uptake, the FDG-PET scans were fused with the original radiotherapy planning-CT including all radiotherapy data (target volumes, radiotherapy plan and original dose distribution) in a software program Mirada. In all fused scans the area between zygoma and hyoid bone was selected and divided into four regions of interest (ROI), which received different amounts of radiation dose. One area without planned radiotherapy (background), secondly the area, which underwent the planned target volume radiation (PTV elective). The PTV elective was divided into the third and fourth ROI; elective target volume (ETV) and the PTV boost (area which received the highest dose of radiotherapy). The FDG-uptake was calculated by the mean SUV (standardized uptake volume) for each area separately. The SUV values were used to compare the four ROIs per PET scan and for comparing the PET scans at 3, 6, 9 and 12 months after treatment. Results: This study showed that the FDG-uptake in PTV elective compared to the FDG-uptake in the background was significantly higher. (SUV mean background: 0.82 (range, 0.6 – 1.1) versus SUV mean PTV elective: 1.36 (range, 0.9 – 1.8)). Thereby, results showed that FDG-uptake was significantly higher when a larger dose of radiation was used (SUV mean ETV: 1.21 (range, 0.9 -1.7) versus SUV mean PTV boost: 1.55(range, 1.0 – 2.3)). Furthermore, these results were still present 12 months after finishing radiotherapy, however, FDG-uptake represented by SUV mean declined in time. Conclusion: Our results indicate that radiotherapy, up to one year after treatment, affects FDG-uptake significantly. Furthermore, a higher amount of radiation dose also resulted in a significant increased FDG-uptake.

Item Type:	Thesis (Thesis)
Supervisor name:	Roodenburg, Prof. dr. J.L.N. and Krabbe, Dr. C.A. and Steenbakkers, Dr. R.J.H.M.
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 11:02
Last Modified:	25 Jun 2020 11:02
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/2232

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