Post-Therapy Surveillance of Head, Neck Cancer With FDG PET 18F-FDG PET as a Routine Posttreatment Surveillance Tool in Oral and Oropharyngeal Squamous Cell Carcinoma: A Prospective Study

Background: Patients with advanced head and neck cancer at initial presentation are at high risk for recurrent disease. The outcome of salvage treatment for recurrent disease is significantly better for recurrences diagnosed at an early stage. Data regarding the use of PET for post-treatment surveillance in patients without a high clinical suspicion for recurrence are limited. Objective: To evaluate the role and timing of FDG PET in the surveillance of patients with advanced oral cavity or oropharyngeal head and neck cancer. Participants/Methods: 48 consecutive patients with Stage III or IV tumors were enrolled. Patients were followed for at least 18 months after completion of therapy. The follow-up included history and examination performed every 3 months without the knowledge of the results of the PET scan and PET scans obtained at 3, 6, 9, and 12 months post-therapy. PET scans were obtained on the day of the clinic visit, either on a dedicated PET or a PET-CT scanner. The interpreting nuclear medicine physicians had access to the findings of the previous clinical exams but not to those from the day of the PET scan. Biopsy results and additional imaging studies served as gold standard to confirm positive findings on the clinical examination or PET scan. Results: 18 patients were diagnosed with malignancy, 11 with recurrent disease or metastases and 7 with second primary tumors. FDG PET identified all malignancies. None of these tumors were detected with routine clinical examination. PET was false positive in 19 patients on ≥1scans and clinical examination revealed falsepositive findings in 13 patients. The common etiologies for false-positive PET scans were mucositis, surgical implants, and osteoradionecrosis. Among the 18 patients diagnosed with malignancy during follow-up, 14 were diagnosed on the 3-month PET scan, 2 on the 6-month scan, and 1 each on the 9-month and the 12-month PET scan. The number of false-positive scans was similar on PET scans obtained at different time points. Overall, the sensitivity, specificity, and accuracy of PET surveillance at any time point was 100%, 43%, and 65%, respectively, compared to 0%, 60%, and 38% for clinical examinations. Seven patients (15%) underwent early salvage therapy based on PET scans; 4 of them were without evidence of disease in the last follow-up. Conclusions: FDG PET is more sensitive than clinical follow-up for surveillance of recurrent or metastatic disease in patients with advanced oral cavity or oropharyngeal cancer. The clinical impact is highest for PET scans obtained at 3 to 6 months after therapy. Reviewer's Comments: This study shows that if the 3-month PET scan is negative, further surveillance with PET in the first year has a low yield and should probably not be obtained given the significant number of falsepositive scans. (Reviewer-Yusuf Menda, MD).