Diagnostic value of 18F-FDG PET/CT and MRI in patients suspected of cancer of unknown primary in the head and neck

BACKGROUND: Cancer of unknown primary (CUP) is diagnostically challenging. Diagnostic strategy remains controversial.

AIM: The aim of this retrospective study was to evaluate the diagnostic value of FDG-PET/CT and MRI in detecting primary tumours in patients presenting with suspected CUP.

METHODS: Patients referred to FDG-PET/CT for suspected CUP were included retrospectively. Data on demographics, diagnostic tests and imaging was collected. Sensitivity and specificity for FDG-PET/CT and MRI were compared using McNemar's test.

RESULTS: In a four year period a total of 329 patients were included, 226 (68.7%) with malignant and 103 (31.3%) with benign pathology. Of the 226 with malignant tumours, 150 (66.4%) had head and neck cancer, the majority of which were with oropharyngeal origin 114 (76.0%).In a subgroup of 80 patients who had both FDG-PET/CT and MRI scans (53.3%), MRI did not significantly increase sensitivity (p = 0.092) in identifying tumour site.

CONCLUSIONS AND SIGNIFICANCE: There was no significant difference in the sensitivity between FDG-PET/CT and MRI in patients with head and neck cancer or CUP. Adding MRI to the diagnostic workup in occult cancer did not significantly improve detection of primary tumours. In case of malignant tumours, 50% were oropharyngeal cancer and required MRI for preoperative planning.