Utility of response assessment PET-CT to predict residual disease in neck nodes: A comparison with the Histopathology.

OBJECTIVE: To assess the ability of Positron Emission Tomography-Computed Tomography (PET-CT) scans to detect residual disease in neck nodes with the Histopathology (HPR) as the gold standard. To obtain a Standardized Uptake Value max cutoff in these patients to predict residual disease in neck.

METHODS: Head and neck squamous cell carcinoma patients who underwent Salvage neck dissection with or without primary site surgery post Concurrent Chemo-Radiotherapy (CCRT) during the period January 2008-December 2017 were included. All patients had response assessment PET-CT scan at 10-14 weeks. Agreement analysis was performed between PET-CT and HPR, fine needle aspiration cytology and HPR. Positive predictive value, Negative predictive value of PET-CT to detect residual neck nodal disease in comparison to HPR was analyzed. A Receiver Operating Characteristic (ROC) curve was plotted between the SUV max values and the HPR. A SUV max cutoff value was obtained from the ROC curve.

RESULTS: A total of 75 patients were included. Thirty-one underwent salvage neck dissection along with surgery for primary disease and 45 underwent salvage neck dissection alone. PET-CT showed good agreement with the HPR to detect residual disease in neck nodes (Kappa=0.604). PET-CT had a PPV and NPV of 87.5% and 79.15% respectively as compared against the HPR. A SUV max cutoff of 4.62 had a specificity of 92.3% and sensitivity of 73.5% to detect residual disease in neck nodes on the HPR.

CONCLUSION: PET-CT surveillance is an accepted treatment strategy. A neck node with SUV max of 4.62 and above is most likely to harbor residual nodal disease.

LEVEL OF EVIDENCE: Level 2b.