Change of FDG Uptake According to Radiation Dose on Squamous Cell Carcinoma of the Head and Neck

Lee, Sang wook; Kim, Jae Seung; Im, Ki Chun; Ryu, Jin Sook; Lee, Hee Kwan; Kim, Jong Hoon; Ahn, Seung Do; Shin, Seong Soo; Yoon, Sang Min; Song, Siyeol; Park, Jin hong; Moon, Dae Hyuk

Abstract

PURPOSE: To evaluate whether positron emission tomography (PET) with 2-[F-18]fluoro-2-deoxy-D-glucose (FDG) can be used to predict of early response to definitive aim radiotherapy (RT) in squamous cell carcinoma of the head and neck using response rate and locoregional control as study endpoints. MATERIALS AND MEHTODS: Twenty-two patients with head and neck cancer underwent a FDG-PET study before RT, after a first dose of 46 Gy, and after a second dose of more than 70 Gy. Standard uptake value (SUV) was calculated for primary tumor (n=22) and neck lymph node (n=10). Attenuation corrected PET scans acquired 60 min after tracer injection were used for evaluation of FDG uptake in tumors. A quantitative FDG uptake index was expressed as SUVlean (corrected for lean body mass). The follow-up time was at least 5 months (range 5-15 months).
RESULTS
A total of 22 primary tumors and 10 metastatic lymph nodes were analyzed in FDG-PET. In the first PET study the mean SUV in the primary tumors and nodes were 6.4 (SD, 2.6) and 4.6 (SD, 2.3), respectively. In the second PET, study performed after 46 Gy RT the mean SUV in primary tumor and node decreased to 2.9 (SD, 1.9, p<0.001) and 1.7 (SD, 1.3) respectively. In the third PET study performed at the full dose (more than 70 Gy), RT the mean SUV in the primary tumors and nodes decreased to 2.3 (SD, 1.5, p<0.001) and 1.5 (SD, 1.1) respectively.
CONCLUSION
FDG uptake in tumors showed a significant decrease after the 46 Gy and more than 70 Gy of RT for squamous cell carcinoma of the head and neck. Reduction of metabolic activity after 46 Gy of radiotherapy is closely correlated with radiation response.