Long-term Results of a Pilot Study Comparing FLT-PET and FDG-PET in the Evaluation of Response to Treatment in Advanced Head and Neck and Esophageal Malignancies

Abstract

Objective: We prospectively compared FDG-PET and FLT-PET in assessing patient responses to induction cetuximab and/or chemoradiotherapy (CRT) for advanced head and neck squamous cell carcinoma (HNSCC) and esophageal cancer (EC). Methods:Sixteen patients were enrolled, 9 with HNSCC and 7 with EC. FDG-PET and FLT-PET scans were performed at baseline and two weeks into chemoradiotherapy (CRT) for patients with EC. Patients with HNSCC received two weeks of induction chemotherapy along with post-induction PET scans prior to starting CRT in addition to the baseline and intra-chemoradiotherapy PET scans. Changes in SUVmax and total lesion glycolysis/ proliferation (TLG/TLP) were compared with baseline.Results: Median follow-up for living patients was 6.0 years. Median overall survival (OS) was 3.3 years and progression-free survival (PFS) was 2.5 years. Patients with HNSCC had higher baseline SUVmax, TLG and TLP than those with EC. Changes in SUVmax, TLG and TLP after induction chemotherapy or during CRT did not correlate with PFS or OS. Those with >40% decline in SUVmax on FDG-PET six weeks after completing CRT had better PFS (p<0.0001) and OS (p=0.0003) than those with less of a response. In addition, >70% decrease in posttreatment TLG correlated with better PFS (p=0.03) and OS (p=0.04). Conclusions:Functional imaging performed early during chemoradiotherapy for advanced HNSCC and EC is feasible. Changes on post-induction and intra-CRT FLT and FDG PET did not correlate with PFS or OS. However, better PFS and OS were seen in patients with >40% decline in SUVmax and >70% decrease in TLG on FDG-PET performed six weeks after completing CRT. Further research is needed to determine the prognostic impact of PET performed during chemotherapy and radiotherapy.