18F-FDG-PET in Guided Dose-Painting with Intensity Modulated Radiotherapy in Oropharyngeal Tumours – Final Toxicity and Disease Outcomes of FiGaRO Phase I Multicentre Feasibility Study
Session type: Poster / e-Poster / Silent Theatre session
The FiGaRO trial assessed the feasibility and safety of delivering a PET-guided radiotherapy (RT) boost to the FDG-avid primary tumour, following 1 cycle of platinum-based induction chemotherapy, in patients with intermediate and high risk locally advanced oropharyngeal cancer.
Patients underwent a planning 18FDG-PET-CT scan, immobilised in the treatment position, after one cycle of induction chemotherapy. The volume of persistent FDG-avidity in the primary tumour was escalated to 71.5Gy/30# (75.85Gy BED), delivered using a simultaneous integrated boost (SIB-IMRT) technique. The clinical radical (primary/nodal) and elective (nodal) volumes were treated to 65Gy/30# and 54Gy/30# respectively. RT was delivered with concomitant platinum-based chemotherapy (following 2 cycles of induction chemotherapy). The primary outcome was incidence of radiation-induced mucosal ulceration at 12 months post-treatment, with an incidence of 10% or less deemed acceptable. Secondary outcomes included acute and other late toxicities and disease outcomes (NCICTCAEv.4.0, RTOG and LENTSOMA scales).
Twenty-four patients were treated between 2014 and 2018, in 2 UK centres. Median follow-up was 36 months (range 4-56). Pre-defined planning target volume and organ at risk dose constraints were met in all cases. All patients completed treatment. There were no incidents of acute grade 4 toxicity. There were no cases of persistent mucosal ulceration at 12 months. RTOG grade 3 mucosal toxicity at 12 months was recorded in 1 patient (atrophy and telangiectasia). This patient had mucosal ulceration at 6 months which resolved by 12 months. One patient was feeding-tube dependent at 12 months, however mucosal integrity was intact. Local control was 83.3% (n=20), and loco-regional control was 79.2% (n=19). Overall survival at 1- and 3-years was 87.5% and 82.9% respectively. Disease-free survival was 83.3% at 1 year and 78.95% at 3 years.
PET-guided dose escalated chemo-radiotherapy, following induction chemotherapy, is feasible and associated with favourable mucosal toxicity rates.