Early response monitoring with 18F-FDG PET/CT after Chemoradiotherapy with Cetuximab in head and neck Squamous Cell Carcinoma Patients (HNSCC)

Objectives To prospectively evaluate if PET/CT a) is able to identify response to treatment as early as one week after end of radio-chemotherapy, b) if PET/CT can identify prognostic markers concerning progression free survival and c) if early PET/CT can identify patients who need additional consolidation therapy.

Methods Total of 50 patients with biopsy proven HNSCC were prospectively enrolled in this single-center study. All patients were treated equally with curative intent chemoradiotherapy (CRT) including Cetuximab(CTX). After that randomized into 2 different arms: with(armA) or without(armB) consolidation CTX from 2-14 weeks after the end of CRT. Patients performed 3 FDG-PET/CT’s in stablished time period: pre-treatment(PET/CT1), 1 week(PET/CT2) and 3 months(PET/CT3) after CRT. Images were assessed by neoplastic lesions evaluated qualitative and quantitatively (size, SUVmax, SUVmean, PETvolume) regarding image response in each scanner period and correlated to disease free survival, neoplastic recurrence/persistence within a minimum 18 months follow-up period. Multivariate Regression analysis was performed to assess independent predictors to progression free survival(PFS).

Results Overall 50 primary lesions and 58 lymph node (LN) metastases were evaluated, with 64% of patients remained disease free, 22% had recurrence and 14% persistent disease. There was no significant difference in distribution of responders and non-responders at post-treatment (PET/CT2 and 3) time points (p>0.05) as well as compared with the reference clinical follow-up. Multivariate regression analysis demonstrated both SUVmax and diameter assessed at PET/CT3 represent independent predictor of progression free survival (PFS). There was also no statistically significant difference in PFS between responders and non-responders by means of PET/CT 2 in both study arms (p>0.05). PET/CT3 imaging responders showed a significantly longer PFS compared to non-responders after the end of consolidation therapy (p< 0.01).

Conclusions Early response(PET/CT2) can be assessed after CRT in HNSCC. PET/CT3 (differences in SUVmax and maximum lesion diameter) are independent predictors for PFS. PET/CT 2 cannot identify high risk patients for consolidation therapy but generally, imaging responders showed a significantly longer PFS compared to non-responders.