6th ICHNO Abstract Book

6th ICHNO 6 th ICHNO Conference International Conference on innovative approaches in Head and Neck Oncology 16 – 18 March 2017 Barcelona, Spain __________________________________________________________________________________________ page 55

PO-115 A [18F] FDG-PET adaptive thresholding algorithm delineation of RT tumour volumes of head and neck cancer L. Deantonio 1 , M. Paolini 1 , L. Vigna 2 , G. Loi 2 , L. Masini 1 , G. Sacchetti 3 , R. Matheoud 2 , M. Brambilla 2 , M. Krengli 1 1 University Hospital Maggiore della Carità, Radiotherapy, Novara, Italy 2 University Hospital Maggiore della Carità, Medical Physics, Novara, Italy 3 University Hospital Maggiore della Carità, Nuclear Medicine, Novara, Italy Purpose or Objective The aim of this study was to evaluate a [18F] FDG-PET adaptive thresholding algorithm (ATA) for the delineation of the biological tumour volume for the radiotherapy (RT) treatment planning of head and neck cancer patients. Material and Methods Thirty-eight patients, who underwent exclusive intensity modulated RT with simultaneous integrated boost (IMRT- SIB) for head-and-neck squamous cell carcinoma (3 oral cavity, 9 nasopharynx, 19 oropharynx, 6 hypopharynx, and 1 larynx cancer) were included in the present study. Thirty-five/38 patients presented a locally advanced disease, and 33/38 received a concomitant chemoradiotherapy treatment. For all patients [18F] FDG- PET/CT was performed in treatment position with the customized thermoplastic mask. Two radiation oncologists defined the primary gross tumour volumes (GTV) using the ATA implemented on the iTaRT workstation (Tecnologie Avanzate, Italy). The algorithm used specific calibration curves that depended on the lesion-to-background ratio (LB ratio) and on the amplitude of reconstruction smoothing filter (FWH). The reproducibility of ATA in volume estimation was determined evaluating the volume overlap of multiple segmentation of the same lesions by different operators. Each primary tumour volume segmented by the ATA (GTV ATA ) was compared to the GTVs contoured on two different sets. In the first, the two radiation oncologist manually draw the standard GTV (GTV ST ) based on clinical information, CT simulation, and magnetic resonance imaging (MRI); in the second, a fixed image intensity threshold method (40% of maximum intensity) of [18F] FDG-PET standardized uptake value was used to define the GTV 40%SUV . Results The ATA previously performed only in a phantom study generate a GTV in all head and neck patients. The mean value of volumes based on the three different methods are reported in Table 1. The GTV ATA was smaller than the GTV ST (17 vs 21 cc); the similarity coefficient (DICE) was 0.7 (Sensibility 66%, specificity 85%). GTV ATA is a part of the GTV ST . The GTV ATA was bigger than the GTV 40%SUV (17 vs 15 cc), the DICE was 0.2. Conclusion The proposed ATA resulted robust and reproducible in a clinical context. The ATA used in the present study allows the delineation of a BTV for dose escalation. A IMRT-SIB with a boost based on GTV ATA is feasible. PO-116 Potential applications of spectral CT imaging in patients with head and neck squamous cell carcinoma B. Peltenburg 1 , J.W. Dankbaar 2 , M.J. Willemink 2 , R. De Bree 3 , T. Leiner 2 1 UMC Utrecht, Radiation Oncology, Utrecht, The Netherlands 2 UMC Utrecht, Radiology, Utrecht, The Netherlands 3 UMC Utrecht, Head and Neck Surgical Oncology, Utrecht, The Netherlands

markers in bioimaging may allow individualization of treatment by dose painting and adaptive radiotherapy. PO-114 Alterations in tumour hypoxia in serial F- MISO/PET-CT during chemoradiation in HNSCC H. Bunea 1 , A. Bunea 1 , L. Majerus 1 , C. Stoykow 2 , M. Mix 2 , A.L. Grosu 1 1 Universitatsklinik Freiburg, Klinik für Strahlenheilkunde, Freiburg, Germany 2 Universitatsklinik Freiburg, Klinik für Nuklearmedizin, Freiburg, Germany Purpose or Objective Tumor hypoxia, a common feature of locally advanced head and neck cancer (HNSCC), is associated with higher malignancy and increased radioresistance. The decrease of tumor hypoxia during fractionated radiation treatment is assumed to be decisive for treatment success. [18F]- Fluoro-Misonidazole PET (F-MISO-PET) allows noninvasive assessment of hypoxia during treatment. The purpose of the present study was to noninvasively assess the time course of tumor hypoxia. Material and Methods A prospective serial imaging study was conducted in patients undergoing definitive chemoradiation (dRCTx, total dose 70Gy) for locally advanced HNSCC, accompanied by cisplatin in weeks 1, 4 and 7. Tumor hypoxia was assessed by F-MISO-PET by static scans acquired 2.5 h p.i. Tumor volumes were determined for FDG PET/CT scans and the coregistered F-MISO/CT scans. At baseline MRI, FDG-PET/CT and F-MISO-PET were acquired (week 0). Additional F-MISO-PET/CT scans were acquired in treatment weeks 2 and 5. Normal sample distribution was confirmed with Shapiro-Wilk test. Unpaired t-test analysis of the mean SUVmax(tumor)/SUVmean(muscle) ratios of F-MISO-PET in weeks 0, 2 and 5 were performed. Significance-level was defined as p<0.005. Results Between 2012 and 2014 18 patients (16 men, two women, mean age 60 years), treated for HNSCC with dRCTx were included. All received a total dose of 70 Gy in 35 fractions. Concomitant cisplatin chemotherapy was administered in weeks 1, 4 and 7. 14 patients had all F-MISO-PET scans, while 4 had two F-MISO-PET scans (week 0, 5). The mean follow-up time was 14.6 months (range: 4 - 28 months). Mean SUVmax(tumor)/SUVmean(muscle) in weeks 0, 2 and 5 were 1.9 (n=18, SD ± 0.1), 1.5 (n=14, SD ± 0.1) and 1.2 (n=18, SD ± 0.1), respectively. Unpaired t-test for SUVmax(tumor)/SUVmean(muscle) between week 0 and 5 was performed, showing a singnificant decrease (p<0.0001). Between weeks 0 and 2 (p=0.0346) and between weeks 2 and 5 the decrease again was highly significant (p=0.0113). In two patients no residual hypoxia was measured in week two, resulting in SUVmax(tumor)/SUVmean(muscle) =1.0. In week 5 this was found in seven patients. In two patients hypoxia had increased in week 2 but decreased in week 5 compared to pre-treatment measurements. In one patient hypoxia had increased by the end of treatment. Conclusion Differences in hypoxia between weeks 0-2, 2-5 and 0- 5, respectively, show statistical significance. This is crucial in the process of re-oxygenation. As concluded in previous works, change of treatment strategy, e.g. by means of dose escalation might be most efficient early during treatment. However further analysis, with more patients and correlation to disease-free and overall-survival are needed.