The influence of F-18 FDG PET-CT fusion on radiotherapy treatment planning for head and neck cancer

Abstract

5534 Background: We report on the influence of F-18 FDG PET-CT fusion on the management of patients with head and neck cancer (HNC). Materials and Methods: From July 2002 to Ocober 2003, 36 patients with intact primary HNC treated with radiation at the Emory Clinic received PET-CT fusion scans as part of treatment planning. Primary site location was oropharynx in 17, nasopharynx in 5, larynx in 4, paranasal sinuses in 3, oral cavity in 2, hypopharynx in 2, and unknown primary in 3. Mean age was 56 years and all were treated with IMRT technique. Three patients received neck dissections before chemoradiation. Platinum based chemotherapy was given concurrently with RT in 31 (86%). CT and FDG –PET scans were obtained for radiotherapy treatment planning. Based on CT simulation data alone, a CT-GTV and CT-PTV were generated . Image fusion between the FDG-PET data and CT images was then performed using manual segmentation based coregistration. Based on this fusion data, a separate PET-GTV and PET-PTV were generated. Results: A change in management occurred in 36%(13) of the patients based on PET-CT findings. PET-CT data upstaged 6 patients and downstaged 4 patients. In the upstaged patients, T (tumor) stage only increased in 1, N(nodal) status increased in 1, both T and N increased in 1 and metastasis was found in 3 . In the downstaged patients, N status decreased from N+ to N0 in 4. 5 patients initially presented with unknown primary and PET confirmed oropharyngeal primaries in 2 of these patients. PET data also detected the presence of a second head and neck primary in one patient and a second primary lung cancer in another patient. The average PET GTV (32cc) was significantly smaller than the average CT-GTV (67 cc) (p=.008) and therefore the PET -GTV was well included in the delineated PTV(based on CT-GTV). Conclusion: PET-CT fusion imaging has significant impact on staging, patient management and determination of the PTV and consequent radiotherapy treatment doses and volumes. In most cases of head and neck cancer, the PET-GTV was congruent with and significantly smaller than the CT-GTV and in some cases, this difference influenced the PTV. No significant financial relationships to disclose.