Abstract Book

ESTRO 37

S362

3 Lausanne University Hospital, Radiationoncology, Lausanne, Switzerland 4 University Hospital of Charleroi, Radiationoncology, Charleroi, Belgium 5 University Hospital Centre of Toulouse, Radiationoncology, Toulouse, France 6 University Hospital Saint-Luc, Radiationoncology, Brussels, Belgium 7 Catharina Ziekenhuis, Radiationoncology, Eindhoven, The Netherlands 8 University hospital of Zurich, Radiationoncology, Zurich, Switzerland 9 Paul Scherrer Institute, Radiationcology, Villigen, Switzerland Purpose or Objective The phase III EORTC 1420 Best of trial is a phase III trial, which compares surgery versus radiotherapy as primary treatment for early stage oropharynx squamous cell carcinoma. Primary endpoint is the patient reported swallowing function over the first year evaluated by the MD Anderson Dysphagia Inventory (MDADI). As this is the primary endpoint of the trial, special attention is required in delineating the swallowing structures in reference to published guidelines [1]. In this work, we analyze the performances of the participating sites with respect to delineation and planning of a Benchmark Case (BC) and assess whether published guidelines are effective as a tool to reduce variability. Moreover the most common inter-observer sources of variation in theses cases were analyzed Material and Methods 25 institutions are currently in the activation process to join the trial. 7 sites have submitted 13 benchmark cases (1 site with 4 submissions, 4 sites with 2 submissions, 1 site with 1 submission).Participating centers were asked to delineate and plan a benchmark case for RTQA credentialing. The patient case chosen as the benchmark was a cT1 cN0 cM0 squamous cell carcinoma of the right tonsil Submissions were centrally reviewed by a radiation oncologist and a medical physicist to study protocol and feedback was given to the centers. Results Most of the participating institutions needed at least two submissions to pass the Benchmark evaluation. The major reason for unacceptable evaluation was the prophylactic CTV inadequately covering the therapeutic CTV ( Graph1 ). In a few cases, the OAR delineation, especially the swallowing structures, needed adjustments. Overall, however we observed no significant difference in performance for the delineation of the different organs at risk. Once passed the volume delineation requirements, the dosimetric evaluation was usually acceptable, with all submissions except one compliant with the dose constraints (thyroid constraint Dmean > 25Gy) Ambiguous delineation instructions and unrealistic dose constraints were identified during case review and the RTQA guidelines were adjusted accordingly to improve future site performance. Conclusion This first RTQA evaluation confirms the importance of pre-trial RTQA to ensure protocol mandates are correctly implemented, especially when introducing new uncommon organ at risks. The observed review results suggest that contouring guidelines reduce the risk of inadequate delineation of swallowing structures. Further analysis will include future benchmark cases in terms of delineation and dosimetry for planning target volumes and organs at risk. PO-0709 Postoperative salvage therapy for early recurrence in oral cavity squamous cell carcinoma A. Hosni 1 , S.H. Huang 1 , K. Chiu 1 , W. Xu 2 , J. Su 2 , A. Bayley 1 , S. Bratman 1 , J. Cho 1 , M. Giuliani 1 , J. Kim 1 , B.

Conclusion Our preliminary results show the impact of clinical- biological factors on different timing of patient’s treatment. Smoke is confirmed to have a negative impact on QoL. HPV associated tumors showed a better perception of pretreatment local symptoms and decrease in all QoL aspects during RT, suggesting that treatment intensity particularly influences this population. Finally, the presence of a caregiver ameliorates QoL outcomes of HNC pts also after treatment completion. J.J. Stelmes 1 , E. Clementel 1 , J. Kaźmierska 2 , M. Ozsahin 3 , M. Tomsej 4 , L. Viellevigne 5 , V. Grégoire 6 , C. Hurkmans 7 , N. Andratschke 8 , D.C. Weber 9 1 EORTC, RTQA, Brussels, Belgium 2 Greater Poland Cancer Center, Radiationtherapy, Poznan, Poland PO-0708 Quality assurance of radiotherapy in the EORTC 1420 Best-of trial. Preliminary results