18F-FDG versus 11C-choline PET/CT for the imaging of advanced head and neck cancer after combined intra-arterial chemotherapy and radiotherapy: the time period during which PET/CT can reliably detect non-recurrence
The purpose of this prospective study was to evaluate the usefulness of 18F-fluorodeoxyglucose (FDG) and 11C-choline positron emission tomography (PET)/computed tomography (CT) for detecting recurrences of advanced head and neck cancer after combined intra-arterial chemotherapy and radiotherapy. Additionally, we surveyed the time period during which an effective negative predictive value could be maintained after the first follow-up PET/CT examination and estimated the optimal timing of a second PET/CT examination for detecting late recurrences. Fifty-three subjects (36 men and 17 women; mean age: 59.4 ± 11.5 years) with advanced head and neck squamous cell carcinoma were recruited. Post-treatment 18F-FDG PET/CT and 11C-choline examinations were performed in all patients between 8 and 12 weeks after combined intra-arterial chemotherapy and radiotherapy. The PET/CT images were evaluated using a patient-based analysis and a lesion-based analysis. All of the patients were prospectively followed for at least 9 months after the post-treatment PET/CT examination, with surveillance using conventional images (including CT and/or MRI) and a physical examination performed every 3 months. Recurrences, as determined using the patient-based analysis, were eventually confirmed in 18, 6 and 5 patients at 3, 4–6 and 7–9 months after the post-treatment PET/CT examination, respectively. The sensitivity and specificity of the 18F-FDG PET/CT and the 11C-choline PET/CT examinations to predict recurrence within 3 months were higher (FDG: 89 and 91%; choline: 83 and 80%, respectively) than for recurrence detection 6 months (FDG: 67 and 90%; choline: 62 and 76%, respectively) and 9 months later (FDG: 59 and 92%; choline: 55 and 75%, respectively). The lesion-based analysis showed that the maximum standardized uptake value of 18F-FDG and 11C-choline in the recurrent lesions were correlated with each other, compared with their relation in scar tissues (R 2 = 0.492 and 0.197, respectively). 11C-choline was not superior to 18F-FDG for the detection of recurrent head and neck cancer. Both modalities had difficulty identifying recurrences at 4–9 months after the post-treatment PET/CT examination. In patients with advanced head and neck cancer who have received combined therapy, a second post-treatment PET/CT examination to check for late recurrences should be performed within 4–6 months after the first post-treatment PET/CT examination.