Impact of Neck PET/CT Positivity on Survival Outcomes - Visual and Quantitative Assessment: Results From ACRIN 6685

Introduction FDG PET/CT was prospectively studied in 287 cN0 head and neck cancer patients in ACRIN 6685, and additional analysis of neck FDG uptake upon recurrence-free survival (RFS) and overall survival (OS) was performed. Patients and Methods Two hundred eight had analyzable data. Survival analysis was performed to compare RFS and OS based on neck FDG visual assessment (VA) and SUVmax. For SUVmax, the optimal thresholds were calculated using conditional inference trees on a randomly selected 70% training data set and validated using the remaining 30% of data. Kaplan-Meier curves with log-rank tests were generated for the patient groups based on VA and optimal SUVmax thresholds, and the hazards ratios (HRs) and 95% confidence intervals (CIs) were also calculated. Hypothesis testing was set at a significance level of 0.05. Results A total of 73.9% of bilateral cN0 and 50.0% of unilateral cN0 were alive at the end of the study with the remaining being dead or lost to follow-up. Overall survival median follow-up time was 24.0 months (interquartile range, 15.8-25.3; range, 0-37.0). A total of 63.3% of bilateral cN0 and 42.5% of unilateral cN0 patients remained disease free during the study. Recurrence-free survival median follow-up time was 23.9 months (interquartile range, 12.4-25.2; range, 0-35.6). Visual assessment of necks by our panel of radiologists was significantly associated with RFS (HR [95% CI], 2.30 [1.10-4.79]; P = 0.02), but not with OS (HR [95% CI], 1.64 [0.86-3.14]; P = 0.13). The optimal SUVmax thresholds were 2.5 for RFS and 5.0 for OS. For SUVmax assessment, applying the optimal thresholds to the 30% test data yielded HRs (95% CIs) of 2.09 (0.61-7.14; P = 0.23) for RFS and 3.42 (1.03-11.41; P = 0.03) for OS. The SUVmax threshold of 5.0 was significantly associated with RFS (HR [95% CI], 5.92 [1.79-19.57]; P < 0.001). Conclusions Neck FDG uptake by VA is significant for RFS. An SUVmax threshold of 5.0 is significantly associated with OS and RFS.