Distant metastases and synchronous second primary tumors in patients with newly diagnosed oropharyngeal and hypopharyngeal carcinomas: Evaluation of ¹⁸F-FDG PET and extended-field multi-detector row CT

Introduction: Patients with oropharyngeal or hypopharyngeal squamous cell carcinoma (SCC) have a high risk of having distant metastases or second primary tumors. We prospectively evaluate the clinical usefulness of ¹⁸F-fluoro-2-deoxyglucose positron emission tomography ( ¹⁸F-FDG PET), extended-field multi-detector computed tomography (MDCT), and their side-by-side visual correlation for the detection of distant malignancies in these two tumors at presentation. Materials and methods: A total of 160 patients with SCC of the oropharynx (n = 74) or hypopharynx (n = 86) underwent ¹⁸F-FDG PET and extended-field MDCT to detect distant metastases or second primary tumors. Suspected lesions were investigated by means of biopsy, clinical, or imaging follow-up. Results: Twenty-six (16.3%) of our 160 patients were found to have distant malignancy. Diagnostic yields of ¹⁸F-FDG PET and MDCT were 12.5% and 8.1%, respectively. The sensitivity of ¹⁸F-FDG PET for detection of distant malignancies was 1.5-fold higher than that of MDCT (76.9% vs. 50.0%, P = 0.039), while its specificity was slightly lower (94.0% vs. 97.8%, P = 0.125). Side-by-side visual correlation of MDCT and ¹⁸F-FDG PET improved the sensitivity and specificity up to 80.8% and 98.5%, respectively, leading to alteration of treatment in 13.1% of patients. A significant difference in survival rates between its positive and negative results was observed. Conclusion: ¹⁸F-FDG PET and extended-field MDCT had acceptable diagnostic yields for detection of distant malignancies in untreated oropharyngeal and hypopharyngeal SCC. ¹⁸F-FDG PET was 1.5-fold more sensitive than MDCT, but had more false-positive findings. Their visual correlation improved the diagnostic accuracy, treatment planning, and prognosis prediction.