POSITRON EMISSION TOMOGRAPHY IN THE DETECTION OF RESIDUAL LARYNGEAL CARCINOMA

Positron emission tomography measures the metabolic activity of tissue . Because metabolism rates are higher in tumors than in normal tissue, positron emission tomography can be used to identify abnormal tissue. Positron emission tomography has proved useful in detecting residual or recurrent tumor in the brain and gastrointestinal tract after defin itive treatment, We selectively used positron emission tomography in a preliminary trial to examine patients with laryngeal cancer who had p reviously been treated with organ-preservation therapy with radiation therapy alone or in combination with induction chemotherapy. These pat ients are often difficult to examine both clinically and radiographica lly because of posttreatment edema and fibrosis. From 1991 to 1993 pat ients at our institution who were treated with either radiation therap y or a combination of induction chemotherapy and radiotherapy for lary ngeal carcinoma were evaluated after treatment. If clinical examinatio n was suspicious for residual tumor or recurrence, a computed tomograp hy or magnetic resonance imaging scan was obtained. In 10 patients nei ther clinical examination nor conventional imaging could absolutely ru le out residual/recurrent carcinoma. In these patients positron emissi on tomography with 2-fluoro-2-deoxy-D-glucose was used to detect disea se. The results from positron emission tomography were compared with t he results from subsequent biopsy (five patients) or clinical follow-u p. Positron emission tomography had a sensitivity of 67% and a specifi city of 57%. The positive predictive value of positron emission tomogr aphy was 67%. The negative predictive value of positron emission tomog raphy was 80%. Positron emission tomography may offer the clinician a useful diagnostic tool for cancer surveillance in organ-sparing treatm ent protocols for patients with laryngeal cancer.