FDG PET/CT within 10 days after induction chemotherapy could predict CCRT response in locally advanced head and neck squamous cell carcinoma: A preliminary study

Objectives After chemotherapy, waiting a minimum of 10 days before performing F-18 FDG PET/CT (FDG PET/CT) is usually recommended. We evaluated the value of FDG PET/CT which is done within 10 days after induction chemotherapy (ICT) in patients with locally advanced head and neck squamous cell carcinoma (HNSCC) for prediction of response to concurrent chemoradiotherapy (CCRT).

Methods Twenty-five patients with locally advanced HNSCC, who underwent ICT with docetaxel, cisplatin, 5-fluorouracil (DCF) followed by sequential CCRT were retrospectively reviewed. All patients underwent FDG PET/CT at staging and within 10 days after completion of 2 or 3 cycles of ICT. Therapeutic responses were evaluated 2 months after the end of CCRT using neck and chest enhanced CT, FDG PET/CT, and laryngoscopy. SUVmax of primary tumor and percentage decrease of SUVmax (dSUVmax) were evaluated for prediction of therapeutic response to CCRT.

Results Among 25 patients, 22 showed complete or partial response to CCRT (responder group) and 3 showed stable or progressive disease (non-responder group). Post-chemotherapy SUVmax of primary tumor was significantly lower in responder group than in non-responder group (3.0 ± 1.8 vs. 7.3 ± 1.1, p=0.006). dSUVmax, post-chemotherapy diameter, and percentage decrease in diameter were not statistically different between groups. Cut-off value of post-chemotherapy SUVmax for prediction of therapeutic response to CCRT was 5.5; AUC (95% C.I) = 0.955 (0.788 - 0.998), sensitivity: 100%, and specificity: 95.5%.

Conclusions This preliminary study suggests that the FDG PET/CT performed within 10 days after 2 or 3 cycles of ICT with DCF in locally advanced HNSCC can be feasible for predicting therapeutic response to CCRT after ICT.