Positron-emission tomography/computed tomography imaging in head and neck oncology: An update

Choice of imaging modality for pre-treatment staging of head and neck cancer impacts TNM staging

PURPOSE

The purpose of this retrospective cohort study was to determine whether there is a difference in the sensitivity of chest computed tomography (CT) versus ¹⁸F-fluorodeoxyglucose positron emission tomography with low-dose nonenhanced CT (¹⁸F-FDG PET/CT or PET/CT) in the detection of distant metastases in head and neck cancer, within a tertiary care setting.

MATERIALS AND METHODS

Patients with head and neck cancer, and known distant metastases, who underwent both ¹⁸F-FDG PET/CT with integrated low-dose nonenhanced CT and diagnostic chest CT prior to initiation of therapy from 2008 to 2017 were included. Two head and neck radiologists, blinded to all patient information and to each other's readings, reviewed the PET/CT or CT chest images for each patient and identified whether distant metastases were present. No radiologist read both modalities for a single patient. Concordance between imaging modalities was quantitatively analyzed using McNemar's test.

RESULTS

27 patients were included. McNemar's mid p-value analysis showed no significant difference in the detection of distant metastases (p = .6875). However, PET/CT detected distant metastases in three patients that chest CT did not, while chest CT identified distant metastatic disease in two patients that were negative on PET/CT.

CONCLUSIONS

While this study did not identify a statistically significant difference in sensitivity, five patients had distant metastases identified on only one of the two modalities. Use of a single modality would have resulted in inaccurate staging in 7-11% of patients in our study. The use of both modalities offers the greatest accuracy when providing stage-adapted oncologic treatment.

PET/CT Evaluation of Head and Neck Cancer of Unknown Primary

The diagnosis of carcinoma of unknown primary in the head and neck is made when there is a metastasis but no primary lesion is identified after physical exam and diagnostic CT or MR imaging. PET/CT is the first step in searching for a primary lesion, followed by more invasive techniques such as endoscopy and surgery. Knowledge of the different tumor histologic types, preferential locations of nodal spread, imaging pitfalls, and other special considerations such as cystic metastases can be helpful in the ultimate identification of primary tumors, which leads to improved overall patient survival.