18F-FDG-PET/CT in assessment of post radiation changes in patients with head and neck squamous cell carcinoma

Objectives Squamous cell carcinoma (SCC) represents more than 90% of all head and neck cancers. On average, 30% of these cases will recur locally within 5 years of initial treatment. These disease pathologies often bear a similar resemblance to pathologic changes caused by radiation therapy (RT) treatment. Therefore, imaging and accurate detection of these cases is crucial in constructing an appropriate treatment strategy. The purpose of this study was to retrospectively review squamous cell carcinoma patients who had undergone RT and look for occurrence of post RT changes on imaging.

Methods Through retrospective study, 102 biopsy proven cases of SCC presenting with head and neck cancer were analyzed. A systematic review of PET/CT reports was performed looking for key words that would indicate signs of post RT changes. The key terms included: osteonecrosis, pneumonitis, inflammation of the gum, epiglottic thickening, thyroid or salivary gland changes, C-spine bone marrow changes, and temporal lobe necrosis. If these phrases were indicated in the PET/CT report, they were included in our patient population.

Results Of the 102 patients reviewed, 19 (18.63%) showed evidence of post radiation changes on imaging with some exhibiting multiple changes. The following describes the radiation-induced changes detected: 7 osteonecrosis (36.84%), 6 pneumonitis (31.58%), 2 epiglottic thickening (10.53%), 1 thyroid gland (5.26%), and 3 temporal lobe necrosis (15.79%).

Conclusions Large numbers of these head and neck cancer patients showed post-radiation changes on PET/CT. Combined functional and morphologic imaging (PET/CT) is better in the detection and characterization of post RT changes than only anatomic imaging modalities such as CT and MRI.