Therapy evaluation of laryngeal carcinomas by tyrosine-pet

One of the major problems in head and neck oncology is determination of tumor status after radiotherapy. Physical examination and conventional imaging by CT and MRI do not always accurately differentiate between residual or recurrent tumor and posttreatment inflammation, fibrosis, edema, or scarring. The feasibility of positron emission tomography (PET) with L-[1-(11)C]-tyrosine (TYR) for therapy evaluation of laryngeal squamous cell carcinomas by identification of residual or recurrent disease after radiotherapy was investigated.

Nineteen patients with laryngeal carcinomas had standard workups with endoscopy and conventional imaging. All subjects underwent a TYR PET scan (PET1) before definitive treatment. For determination of tumor status, a second TYR PET scan (PET2) was performed 3 months after radiotherapy. At the time of scanning, seven patients were clinically suspected of having residual disease, and in these cases, additional CT imaging and biopsies during endoscopy were performed. During the minimal follow-up period of 29 months, six patients had clinical suspicion of recurrent disease. In these six cases, a third TYR PET (PET3), CT imaging, and biopsy were performed.

All pretreatment tumors were depicted by TYR PET (PET1). Three months after radiotherapy, sensitivity and specificity of TYR PET (PET2) for discrimination between residual tumor and benign posttreatment tissue changes were both 100%, and for CT, 50% and 67%, respectively. For detection of recurrent tumor during follow-up, sensitivity and specificity of TYR PET (PET3) were also 100%, and CT, 75% and 50%, respectively.

Dynamic TYR PET is an accurate imaging modality for therapy evaluation in detection of residual and recurrent disease with higher sensitivity (100%) and specificity (100%) for discrimination of tumor status by TYR PET compared with conventional imaging.