Response assessment by combined PET-CT scan versus CT scan alone using RECIST in patients with locally advanced head and neck cancer treated with chemoradiotherapy

Purpose: RECIST have limitations when applied to potentially curable locally advanced squamous cell carcinoma of the head and neck (SCCHN). [F-18]fluorodeoxyglucose-positron emission tomography (PET) scan may be useful in assessing treatment response and predicting patient outcome. Patients and methods: We studied patients with previously untreated stages III-IVb SCCHN treated with primary concurrent chemoradiotherapy on five prospective clinical trials. Response was assessed by clinical exam, computed tomography (CT), and PET portions of combined PET-CT scan similar to 8 weeks after completion of chemoradiotherapy. Results: Fifty-three patients were analyzed. Complete response (CR) was demonstrated in 42 patients (79%) by clinical exam, 15 (28%) by CT, and 27 (51%) by PET. CR as assessed by PET, but not as assessed by clinical exam or CT using RECIST, correlated significantly with progression-free status (PFS) (P < 0.0001). The 2-year PFS for patients with CR and without CR by PET was 93% and 48%, respectively (P = 0.0002). Conclusions: A negative PET scan on combined PET-CT after chemoradiotherapy is a powerful predictor of outcome in patients receiving curative chemoradiotherapy for SCCHN. PET-CT is indicated for response evaluation in this setting to improve the accuracy of post-treatment assessment by CT.