ESTRO 36 Abstract Book

S583 ESTRO 36 _______________________________________________________________________________________________

Purpose or Objective Squamous cell carcinoma (SCC) of buccal mucosa has a high incidence of locoregional failure. Its aggressive behavior and the change of lymphatic and vascular drainage after surgery make the design of radiotherapy difficult. The aim of this study is to analyze failure patterns and prognostic factors in patients with locally advanced buccal cancer after postoperative intensity modulated radiotherapy (IMRT). Material and Methods Between January 2007 to October 2012, 84 patients with histological confirmed SCC of buccal mucosa underwent surgery followed by postoperative IMRT were retrospectively analyzed.. All patients were stage III/IV buccal cancer. The high-risk clinical target volume (CTV) covered the surgical tumor bed and ipsilateral or bilateral upper neck. The median dose to high-risk CTV was 60Gy. Analyzed end-points were overall survival (OS), local recurrence-free survival, loco-regional recurrence-free survival, supra-mandibular notch recurrence-free survival, distant metastasis-free survival, prognostic factors and patterns of failure. Results The median follow up was 51 months (range, 2-112 months). The first recurrent sites were local tumor bed (17 patients) with or without regional/distant recurrence. The median time from treatment completion to first locoregional recurrence was 7.3 months. Of the 17 patients with local recurrence, 11 exhibited the supra- mandibular notch recurrence; most were classified as marginal failure. The estimated 4-year local failure-free, locoregional failure-free, distant metastasis-free and overall survival rates were 72%, 63.3%, 85.9% and 68.8%. In multivariate analysis, lymphovascular invasion (P = 0.002), N2 disease (P = 0.003), and ratio of tumor thickness to tumor size larger than 1/3 (P = 0.014) were independent prognostic factors for overall survival. Patients received tumor excision with maxillectomy was a predictive factor for the development of supra-mandibular notch recurrence. Conclusion SCC of buccal mucosa is a highly aggressive form of oral cavity cancer with a high locoregional failure rate and most locoregional recurrences led to lethal events. Design of postoperative IMRT for buccal cancer, especially CTV delineation, based on failure patterns and clinicopathological prognostic factors might transfer into better disease control. EP-1061 Towards a validated Decision Aid Tool for advanced larynx cancer patients A.J. Berlanga 1 , M. Petersen 2 , F. Hoebers 1 , S. Delbressine 1 , M. Van den Breke 2,3,4 , P. Lambin 1 1 Maastro Clinic, GROW School for Oncology and Developmental Biology- Maastricht University Medical Centre, Maastricht, The Netherlands 2 The Netherlands Cancer Institute, Department of Head and Neck Surgery and Oncology, Amsterdam, The Netherlands 3 Academic Medical Center, Department of Oral and Maxillofacial Surgery, Amsterdam, The Netherlands 4 University of Amsterdam, Institute of Phonetic Sciences, Amsterdam, The Netherlands Purpose or Objective Advanced larynx cancer patients may be eligible for more than one treatment: laryngectomy, radiotherapy, chemoradiation, or combinations thereof. These treatments have a distinct impact on quality of life (e.g. disfigurement, speech, swallowing problems), and outcomes depending on TNM-classification. To empower these patients to participate in shared- decision making, we are creating a web-based Patient

Purpose or Objective A standardized way of converting PET signals into target volume is not yet available. The aim of this study was to evaluate a [18F] FDG-PET adaptive thresholding algorithm 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 (92.1%), and 30/38 patients (78.9%) received a concomitant chemoradiotherapy. For all patients, [18F] FDG-PET/CT was performed in treatment position with the customized thermoplastic mask. Two radiation oncologists defined the primary biologic tumour volumes (BTV) using the adaptive thresholding algorithm 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 evaluation of reproducibility of adaptive thresholding algorithm for volume estimation was determined by the volume overlap of multiple segmentation of the same lesion by two radiation oncologists. Each primary tumour volume was segmented by the adaptive thresholding algorithm (BTV ATA ). The target volumes for the primary tumours previously delineated on the planning computed tomography (CT) scan using anatomic imaging (CT and MRI) (gross tumour volume standard GTV ST ) and a fixed image intensity threshold method (40% of maximum intensity) of [18F] FDG-PET standardized uptake value (GTV 40%SUV) were used to perform a volumetric comparison. Results The algorithm generated a tumour volume in all but two patients. The mean values with standard deviation (SD) of volumes based on the three different methods were reported in Table 1. The BTV ATA was significantly smaller than the GTV ST (17 vs. 21 cc, p= 0.04); the conformity index (CI) was 0.46, and the similarity coefficient (DICE) was 0.7 (Sensibility 66%, specificity 85%). BTV ATA is a part of the GTV ST . The BTV ATA was bigger than the GTV 40%SUV (17 vs. 15 cc) but the difference was not statistically different (p> 0.05), the CI was 0.8 and the DICE was 0.2. Table 1. Tumour Volumes defined by the three different methods. GTV Mean Volume (cc) Ranges Standard Deviation GTV ST 21.4 4.5 – 66.3 ±16.0 GTV 40%SUV 14.7 1.3 – 58.5 ±13.7 GTV T ATA 17.2 1.5 – 61.5 ± 12.8 Conclusion The proposed adaptive thresholding algorithm resulted robust and reproducible in the clinical context of head and neck tumours. The tumour volumes obtained by the algorithm were a part of the GTV ST and were similar to GTV 40%SUV. This tumour volume could allow the delineation of a BTV for dose escalation in head and neck cancer treated with IMRT-SIB. EP-1060 Analysis of failure patterns and prognostic factors after postoperative IMRT for buccal cancer Y.W. Lin 1 , L.C. Lin 1 1 Chi Mei Medical Center, Department of Radiation Oncology, Tainan, Taiwan