Accuracy of FDG-PET-CT response assessment following (chemo)radiotherapy for locally advanced larynx and hypopharyngeal carcinoma


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Finbar Slevin1,Sriram Vaidyanathan1,Mehmet Sen1,Andrew F Scarsbrook1,Robin J D Prestwich1
1St James' Institute of Oncology

Abstract

Background

(Chemo)radiotherapy is an established organ-preserving treatment for head and neck squamous cell carcinoma. Previous studies evaluating the accuracy of response assessment 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) positron-emission tomography-computed tomography (PET-CT) following chemo(radiotherapy) have included only small numbers of patients with larynx and hypopharynx carcinoma.  The aim of this study was to assess the diagnostic accuracy of delayed response assessment PET-CT following chemo(radiotherapy) for larynx and hypopharynx squamous cell carcinoma.

Method

Patients with larynx or hypopharynx squamous cell carcinoma who underwent a baseline FDG PET-CT between June 2009 and November 2014 and were treated with (chemo)radiotherapy were identified retrospectively. Assessment of diagnostic accuracy of delayed response assessment FDG PET-CT was made by correlation with clinical follow up and pathological findings.

Results

35 patients were identified, including 18 with hypopharyngeal and 17 with laryngeal carcinomas.  33/35 (94%) had stage III/IV disease.  Median follow up was 32 months. Median time to FDG PET-CT following (chemo)radiotherapy was 18 weeks. 20 of 35 (57%) patients had an overall complete metabolic response. 19 of 32 (59%) patients with an assessable primary and 20 of 26 (77%) with assessable nodal disease had a complete metabolic response.  Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for response assessment FDG PET-CT for primary and nodal sites respectively was 100%, 73%, 46% and 100%, and 83%, 95%, 83% and 95%.  Three patients were found to have residual nodal masses on response assessment FDG PET-CT which were FDG-negative and managed with clinical observation; all remained disease free on follow up.

Conclusion

Response assessment FDG PET-CT following (chemo)radiotherapy for larynx and hypopharynx cancer has a high NPV for both primary site and lymph nodes and can be used to guide treatment decisions.  The PPV of residual PET uptake at the primary tumour site is limited, and requires examination and biopsy to exclude residual disease.