Head and neck cancers: Post-therapy changes in muscles with FDG PET-CT

BACKGROUND: FDG PET-CT plays a critical role in the management of head and neck cancer patients. After therapy, many patterns of altered physiologic FDG uptake have been recognized. In our institution, we noticed patterns of head and neck muscle uptake that were unique in the post-therapy scans of head and neck cancer patients. MATERIALS AND METHODS: A total of 32 patients with head and neck cancers who had both pretherapy and posttherapy FDG PET-CT scans were retrospectively analyzed. Regional anatomic muscle groups that had increased PET uptake on either pretherapy or post-therapy scans were identified. RESULTS: On the pretherapy scans, the majority of patients (24/32 patients) did not have increased PET activity in the predefined muscle groups. On the post-therapy scans, the majority of patients (25/32 patients) demonstrated increased uptake in at least 1 head and neck muscle group, with an average of 3 muscle groups per patient. The muscle groups with the greatest frequencies were the prevertebral (50%), the accessory neck (47%), the posterior paravertebral (47%), and the scalene muscles (38%). Relative to pretherapy scans, the mean intensity of the post-therapy elevations corresponded to greater SUVs. CONCLUSION: FDG PET-CT scan commonly depicts an elevated FDG muscle uptake in all regional anatomic muscle groups in the post-therapy head and neck cancer patient. This uptake should be considered as a consequence of treatment and perhaps changes in altered biomechanics, and not be confused with residual or recurrent neoplastic activity.