[Diagnosis with (18)F-FDG PET scan after larynx preservation by primary radiochemotherapy]

In a group of 20 patients undergoing chemoradiation for larynx organ preservation after diagnosis of laryngeal and hypopharyngeal carcinoma, (18)F-fluordeoxyglucose positron emission tomography ((18)F-FDG-PET) was performed before the start of therapy. After i.v. application of 240 MBq FDG, a dynamic PET in 3-D-mode was performed over 90 min (Siemens CTI ECAT EXACT HR(+)). Analysis was done visually and semiquantitatively (60-90 min p.i.) following iterative reconstruction. Additional (18)F-FDG-PET investigations were done and correlated with the clinical outcome in 16/20 patients at 3 months and in 14/20 patients at 6 months after the end of therapy.

In 17/20 patients (85%), the preclinical (18)F-FDG-PET correlated well with the histologically confirmed primary tumor. Three cases were false negatives. In one case this was due to an increased glucose value (203 mg%). After 3 months, 8/13 (62%) patients showed a positive correlation between clinical and PET results (sensitivity 100%, specificity 70%). After 6 months, 9/11 (82%) patients presented clinically normal PET results. PET results were false negative in one case (sensitivity 67%, specificity 88%).

The data of our trial slightly reduce the enthusiasm of early (18)F-FDG-PET detection of residual disease after chemoradiation in resectable laryngeal or hypopharyngeal cancer. Further trials should optimize the calculation integrating the exact quantification of glucose metabolism with the aim of improving sensitivity and specificity.