Prospective study of 18FDG-PET in the detection and management of patients with lymph node metastases to the neck from an unknown primary tumor. Results from the DAHANCA-13 study.

BACKGROUND: The benefit of a complementary fluorodeoxyglucose-positron emission tomography (FDG-PET) scan to standard workup for carcinoma of unknown primary (CUP) and metastatic neck lesions was prospectively studied.

METHODS: Sixty-seven patients underwent standardized diagnostic workup according to national guidelines including panendoscopies, multiple mucosal biopsies, and diagnostic CT/MRI scans. Median follow-up was 40 months (range, 2-65 months).

RESULTS: In 60 eligible patients, FDG-PET indicated a primary tumor or metastatic disease in 30 patients (50%). Additional investigations confirmed a primary tumor in 18 patients: hypopharynx in 5, oropharynx in 5, nasopharynx in 2, lung in 1, axilla in 1, bone in 1, rectum in 1, as well as multiple metastatic lesions from CUP in 2 patients. In retrospect, MRI was able to detect 1 of the PET-detected primaries, leading to an overall detection rate of PET of 29% in CUP. A therapeutic change of treatment was made in 25% as a consequence of FDG-PET. PET before panendoscopy demonstrated fewer false-positive pathological foci.

CONCLUSION: FDG-PET is a valuable tool in addition to conventional extensive workup in CUP and neck metastases. Consequently, FDG-PET is now recommended as an early diagnostic modality in the workup of these patients.