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


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Delali Adjogatse1,Andriana Michaelidou2,Yae-Eun Suh1,Lucy Pike2,Christopher Thomas3,Owain Woodley4,Beatriz Sanchez Nieto5,Tom Rackley6,Nachi Palaniappan6,Vetrisudar Jayaprakasam7,Mererid Evans6,Mary Lei1,Sally Barrington2,Teresa Guerrero Urbano1
1Dept of Oncology, Guy's and St Thomas NHS Foundation Trust, London, UK,2King's College London and Guy's and St Thomas PET Centre, London, UK, School of Biomedical Engineering and Imaging Sciences, King's College London, King's Health Partners, London, UK,3Department of Medical Physics, Guy's and St Thomas NHS Foundation Trust, London, UK, King's College London and Guy's and St Thomas' PET Centre, London, UK, School of Biomedical Engineering and Imaging Sciences, King's College London, King's Health Partners, London, UK,4Medical Physics Dept, Velindre University NHS Trust, Cardiff, UK,5Faculty of Physics, Pontificia Universidad Catolica de Chile, Santiago, Chile,6Dept of Oncology, Velindre University NHS Trust, Cardiff, UK,7Wales Research and Diagnostic PET Imaging Centre, Cardiff, UK

Abstract

Background

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.

Method

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).

Results

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.

Conclusion

PET-guided dose escalated chemo-radiotherapy, following induction chemotherapy, is feasible and associated with favourable mucosal toxicity rates.