Occult primary tumors of the head and neck - Lack of benefit from positronemission tomography imaging with 2-[F-18]fluoro-2-deoxy-D-glucose

BACKGROUND. Patients who present with squamous cell carcinoma metastatic to cervical lymph nodes and no clinically apparent primary site present a the rapeutic dilemma. Positron emission tomography imaging with 2-[F-18]fluoro- 2-deoxy-D-glucose (FDG-PET) has been shown to be useful for the examination of known primary tumors. This study was undertaken to determine whether FD G-PET imaging improves detection of occult primary tumors in patients with metastatic squamous cell carcinoma in the lymph nodes of the head and neck. METHODS. Thirteen patients with pathology proven cervical lymph node metast ases from clinically occult primary squamous cell carcinomas were evaluated prospectively with FDG-PET, in addition to standard clinical and radiograp hic techniques, as part of their pretreatment diagnostic evaluation. Direct panendoscopy and biopsy were performed on all patients in an attempt to de tect primary tumor sites and to characterize them histologically. RESULTS. A primary squamous cell carcinoma was confirmed after panendoscopy and biopsy in 3 of the 13 patients. The site of the primary tumor was corr ectly identified with FDG-PET in only one of these three patients. The FDG- PET study suggested a primary tumor location where no tumor was found in 6 of 13 patients; for 5 other of the 13 patients, the FDG-PET results were ne gative and no primary was found. No primary tumor locations were identified by computed tomography, magnetic resonance imaging, or direct panendoscopy . FDG-PET imaging correctly detected the location of the primary tumor in 1 patient (8%) and provided apparent false-positive results for 6 (46%) of t he 13 patients. CONCLUSIONS. FDG-PET imaging did not significantly improve detection of unk nown primary squamous cell carcinomas in patients with metastases to lymph nodes of the neck A high percentage of results were apparent false-positive . Cancer 1999;86:114-8, (C) 1999 American Cancer Society.