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 definitive treatment, We selectively used positron emission tomography in a preliminary trial to examine patients with laryngeal cancer who had previously been treated with organ-preservation therapy with radiation therapy alone or in combination with induction chemotherapy. These patients are often difficult to examine both clinically and radiographically because of posttreatment edema and fibrosis. From 1991 to 1993 patients at our institution who were treated with either radiation therapy or a combination of induction chemotherapy and radiotherapy for laryngeal carcinoma were evaluated after treatment. If clinical examination was suspicious for residual tumor or recurrence, a computed tomography or magnetic resonance imaging scan was obtained. In 10 patients neither clinical examination nor conventional imaging could absolutely rule out residual/recurrent carcinoma. In these patients positron emission tomography with 2-fluoro-2-deoxy-D-glucose was used to detect disease. The results from positron emission tomography were compared with the results from subsequent biopsy (five patients) or clinical follow-up. Positron emission tomography had a sensitivity of 67% and a specificity of 57%. The positive predictive value of positron emission tomography was 67%. The negative predictive value of positron emission tomography was 80%. Positron emission tomography may offer the clinician a useful diagnostic tool for cancer surveillance in organ-sparing treatment protocols for patients with laryngeal cancer.