Imaging strategy for response evaluation to chemoradiotherapy of the nodal disease in patients with head and neck squamous cell carcinoma.

Background: Definitive chemoradiotherapy (CRT) is used to treat lymph node metastatic head and neck cancer patients. Regional control of the neck disease is important to improve the prognosis, and the accuracy of the method used to evaluate the metastatic lymph node(s) after CRT is crucial to the decision-making process for any following salvage surgery.

Methods: Patients undergoing CRT were divided in two groups of patients of those showing complete clinical response (CR) and those showing clinical non-response (non-CR), as assessed by computed tomography (CT) and/or magnetic resonance imaging (MRI), ultrasonography, fluorodeoxyglucose-positron emission tomography (FDG-PET), and fine needle aspiration cytology. The responses (CR vs. non-CR) were compared with the actual clinical outcomes. For the interim analysis, the study period was broken down into two periods, namely, the exploratory phase (patients treated between January 2002 and April 2012) and the validating phase (patients treated between May 2012 and January 2014).

Results: The sensitivity, specificity, and accuracy were as follows: CT and/or MRI, 66.7, 73.8, and 72.8 %, respectively, in the exploratory phase; ultrasonography, 91.7, 70.6, and 73.4 %, respectively, in the exploratory phase and 80.0, 82.8, and 82.4 %, respectively, in the validating phase; FDG-PET, 50.0, 97.5, and 91.3 %, respectively, in the exploratory phase and 60.0, 100, and 94.1 %, respectively, in the validating phase; cytology, 68.4, 95.9, and 90.3 %, respectively, in the exploratory phase and 66.7, 100, and 85.7 %, respectively, in the validating phase.

Conclusions: Based on our results, CT and/or MRI appear to be inadequate methods for the evaluation of the response of lymph node(s) to CRT. In contrast, ultrasonography appears to be a highly sensitive and useful tool for positive screening at 6-8 weeks after CRT, and FDG-PET appears to be a highly specific and useful tool for negative screening at 8-12 weeks after CRT.