Adaptive Radiotherapy for Cancer of the Head and Neck guided by Intra-treatment ¹⁸F-FDG-PET and MRI scanning – Proposal for a Phase 1 feasibility study
Session type: Poster / e-Poster / Silent Theatre session
Loco-regional failure remains the main cause of recurrence for locally advanced head and neck squamous cell carcinoma (HNSCC). Increasing the radiation dose may improve local control. A simultaneous integrated boost (SIB-IMRT) technique can be used to create isotoxic dose escalated plans and optimally timed imaging could identify tumours likely to benefit. We propose a prospective adaptive radiotherapy study, using MRI and 18F-FDG-PET-CT, to assess feasibility and toxicity of this approach.
Recruitment aim is 40 patients. Patients requiring chemo-radiotherapy (CRT) for intermediate/high risk SCC Oropharynx and Hypopharynx will be eligible. All will commence with standard CRT; 70Gy/35# and weekly cisplatin 35mg/m2 (or carboplatin AUC 1.5). An 18F-FDG-PET and anatomical MRI will be performed pre-treatment, then repeated at fraction 11 (+/- 1) in the treatment position and immobilisation shell. Patients with both radiological and metabolic complete response will continue with standard CRT. Those with residual disease will be dose escalated. Criteria for escalation includes: residual PET-avid lesion with SUVmax ≥4.0 and an anatomical correlate (CT/MRI), or residual MRI lesion of intermediate T2 signal ≥1cm diameter in short axis. The intra-treatment scans will be used to segment and plan the boost volume. The RT plan will be adapted to include the boost from fraction 21. This sub-volume will receive a total dose of 76.77Gy/35# BED. Additional procedures for exploratory analyses will include: acquisition of diffusion weighted (DW) MRI sequences, repeat MRI at week 4 of RT, and collection of blood and saliva samples. The primary outcome is incidence of grade ≥3 late mucosal toxicity at 12 months post-CRT, with an incidence of 10% or less deemed acceptable. Secondary outcomes include acute and other late toxicities, disease outcomes and correlation of DW-MRI and PET imaging with tumour response.
Image-guided adaptive dose escalation merits investigation in head and neck cancer patients.