Results of pretherapeutic lymph node diagnosis in head and neck cancer: Clinical value of (18)-fluorodeoxyglucose positron emission tomography (PET).

Background: Histological studies demonstrate that there is a high percentag e of occult nodal metastasis in head and neck malignomas. Patients with pos itive lymph nodes have a comparatively worse prognosis. A neck dissection i s required in these cases. By demonstrating morphological abnormalities, im aging procedures like ultrasound, computer tomography (CT), and magnetic re sonance imaging (MRI) can provide important initial informations about poss ible malignant alteration of the lymph nodes. Positron emission tomography (PET) allows functional metabolic imaging of a suspected tumor site. The ai m of this study was a comparative evaluation of different diagnostic proced ures with special emphasis on the value of PET in the pretherapeutic diagno sis of nodal spread in head and neck cancer. Patients and Methods: Forty pa tients (28 male and 12 female) with a suspected malignoma in the head and n eck region underwent clinical examination including palpation of the neck s ides, ultrasound, CT, and PET to detect a nodal spread of the malignancy. F ifty neck dissections were performed in 28 patients. Lymph node biopsies we re performed in the remaining patients. The results of the diagnostic proce dures were compared to the histology and the clinical course of the patient s. The mean follow-up period was 12.5 months. Results: A nodal metastasis w as verified in 35% of all cases. Sensitivity of all imaging procedures incl uding PET was 82 %. Palpation had a sensitivity of only 61 %. Specifity was 85 % for ultrasound, 94% for CT and palpation, and 87% for PET. PEI produc ed false negative results in 13.4% of all cases. Inflammation was detected in these cases. The positive predictive value was marginally better for PET than for ultrasound (77% vs. 75 %). It proved to be lower than the values for palpation (86 %) and CT (88%). Negative predictive value was 90-91% for all imaging procedures. Conclusion: In the primary diagnosis of nodal alte rations in the head and neck region, a PET scan has the same diagnostic val ue as ultrasound or CT. By imaging the metabolism of a suspected nodal meta stasis, PET can help to improve the assessment of regions with uncertain an atomic features. To avoid false positive results, acute and chronic inflamm atory alterations have to be ruled out before the PET imaging.