Abstract

Background: Concomitant chemoradiation therapy (CRT) is widely accepted as a primary treatment of advanced head and neck squamous cell carcinoma (HNSCC). However, controversy exists regarding the treatment of patients with no clinically evident nodal disease after CRT. PET/CT imaging has therefore become increasingly popular to aid in the selection of patients who would benefit from post-CRT neck dissection. However, there are several competing concerns regarding the timing of PET/CT and planned neck dissection. The aims of this study were to assess how (i) the detection of residual neck disease by PET/CT and (ii) the incidence of viable carcinoma in neck dissection specimens differ with time after CRT for advanced HNSCC.

Methods: Retrospective review of 121 patients who underwent PET/CT and planned neck dissection following
primary CRT for N2 or greater HNSCC. The sensitivity and specificity of PET/CT for detection of residual neck disease after CRT were determined. Rates of negative, non-viable, or positive pathologic results in neck dissection specimens were also assessed.

Results: PET/CT results following CRT were analyzed for a total of 116 neck sides. The sensitivity and specificity of PET/CT for residual neck disease were 42.3% and 90.4%, respectively. Specificity tended to increase with time, whereas sensitivity decreased. Sixty patients underwent planned neck dissection earlier than 12 weeks following mcompletion of CRT, and 61 patients underwent neck dissection 12 weeks or later. Viable carcinoma was detected in 31.4% of surgical specimens. Rates of negative, non-viable, or positive pathologic results were similar in neck dissections performed before versus after 12 weeks following CRT (p=0.951).
 

Conclusions: PET/CT is limited by low predictive value, but specificity tends to increase with time. Rates of viable carcinoma do not differ with time; histologic evidence of tumor lysis does not appear to continue beyond 12 weeks after CRT.