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Top Line: Interpreting results of survelliance PET after chemoradiation for oropharyngeal squamous cell carcinoma (SCC) can be confusing.
The Study: The prospective Alberta Cancer Registry was retrospectively queried to identify all patients undergoing PET surveillance within one year of definitive treatment for oropharyngeal SCC. Of 190 patients identified, 103 had positive PET findings defined as a non-physiologic SUV ≥2.5. The majority of scans were performed within 3 months of treatment completion and only a small handful at 6-12 months out. The good news is that the negative predictive value is virtually 100%. The bad news is that over half (59%) of those with PET-avid findings were clinically free of disease, determined either with salvage resections or subsequent radiographic clearance without treatment. The biggest predictors of false positives were p16-positivity (OR 3.7), treatment with definitive chemoradiation (OR 3.3), and <10 pack year history (OR 3.2). The ROC curve demonstrated the optimal SUV threshold was roughly 5 following both definitive surgery, where it boosted specificity to 74%, and definitive chemoradiation, where it boosted specificity to 80%.
Bottom Line: PET-avidity alone may not warrant aggressive salvage neck dissections in patients treated with definitive chemoradiation for low-risk oropharyngeal SCC, particularly if the max SUV is <5. | Sivarajah, JAMA Otolaryngol Head Neck Surg 2018