Multicenter Trial of [18F]fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Staging of Head and Neck Cancer and Negative Predictive Value and Surgical Impact in the N0 Neck: Results From ACRIN 6685.

PURPOSE: The objective of this study was to determine the negative predictive value (NPV) of positron emission tomography (PET)/computed tomography (CT) for the clinically N0 neck on the basis of neck dissection. METHODS: Participants with newly diagnosed, first-time, head and neck squamous cell carcinoma (HNSCC) and at least one clinically N0 neck side for which dissection was planned were included. A total of 287 participants were prospectively enrolled from 23 American College of Radiology Imaging Network-qualified institutions. PET/CT was compared with findings at neck dissection. RESULTS: PET/CT scans and pathology findings were available for 270 N0 neck sides from 212 participants. For visual assessment, the NPV specific to the clinical-N0 sides was 0.868 (95% CI, 0.803 to 0.925). For dichotomized maximum standardized uptake value, the NPVs specific to the nodal basins were 0.940 (95% CI, 0.928 to 0.952) and 0.937 (95% CI, 0.925 to 0.949) at prespecified cutoffs of 2.5 and 3.5, respectively. The optimal cutoff maximum standardized uptake value was determined to be 1.8, with an NPV of 0.942 (95% CI, 0.930 to 0.953). The PET/CT-informed surgical treatment plan was changed in 51 of 237 participants (22%) compared with the PET/CT-blinded surgical plan. In 34 participants (14%), this led to planned dissection of additional nodal levels. In 12 participants (5%), this led to fewer planned dissected nodal levels. Negative PET/CT scans in N0 necks was true negative in 87% and false negative in 13%. CONCLUSION: [18F]fluorodeoxyglucose-PET/CT has high NPV for the N0 neck in T2 to T4 HNSCC. The surgical treatment plans on the basis of PET/CT findings may be changed in approximately 22% of this group. These findings suggest that [18F]fluorodeoxyglucose-PET/CT may assist the clinician in deciding on the best therapy for the clinically N0 neck in HNSCC. Well-designed clinical trials should be performed to test the outcome of omitting neck dissection by using PET/CT.

Repeatability of 18F-FDG PET/CT in Advanced Non-Small Cell Lung Cancer: Prospective Assessment in 2 Multicenter Trials.

UNLABELLED: PET/CT with the glucose analog (18)F-FDG has several potential applications for monitoring tumor response to therapy in patients with non-small cell lung cancer (NSCLC). A prerequisite for many of these applications is detailed knowledge of the repeatability of quantitative parameters derived from (18)F-FDG PET/CT studies. METHODS: The repeatability of the (18)F-FDG signal was evaluated in 2 prospective multicenter trials. Patients with advanced NSCLC (tumor stage III-IV) underwent two (18)F-FDG PET/CT studies while not receiving therapy. Tumor (18)F-FDG uptake was quantified by measurement of the maximum standardized uptake value within a lesion (SUVmax) and the average SUV within a small volume of interest around the site of maximum uptake (SUVpeak). Analysis was performed for the lesion in the chest with the highest (18)F-FDG uptake and a size of at least 2 cm (target lesion) as well as for up to 6 additional lesions per patient. Repeatability was assessed by Bland-Altman plots and calculation of 95% repeatability coefficients (RCs) of the log-transformed SUV differences. RESULTS: Test-retest repeatability was assessed in 74 patients (34 from the ACRIN 6678 trial and 40 from the Merck MK-0646-008 trial). SUVpeak was 11.57 ± 7.89 g/mL for the ACRIN trial and 6.89 ± 3.02 for the Merck trial. The lower and upper RCs were -28% (95% confidence interval [CI], -35% to -23%) and +39% (95% CI, 31% to 54%) in the ACRIN trial, indicating that a decrease of SUVpeak by more than 28% or an increase by more than 39% has a probability of less than 2.5%. The corresponding RCs from the Merck trial were -35% (95% CI, -42% to -29%) and +53% (95% CI, 41% to 72%). Repeatability was similar for SUVmax of the target lesion, averaged SUVmax, and averaged SUVpeak of up to 6 lesions per patient. CONCLUSION: The variability of repeated measurements of tumor (18)F-FDG uptake in patients with NSCLC is somewhat larger than previously reported in smaller single-center studies but comparable to that of gastrointestinal malignancies in a previous multicenter trial. The variability of measurements supports the definitions of tumor response according to PET Response Criteria in Solid Tumors.