ESTRO 36 Abstract Book

S352 ESTRO 36 _______________________________________________________________________________________________

Grade I: good healing, without necrosis or fibrin Grade II: fokal mucosal necrosis, anastomosis is stable Grade III: circular mucosal necrosis and / or ischemia in the depthof the distal bronchus Grade IV: transmural bronchial necrosis with instability Grade V: perforation of the anastomosis, insufficiency Results The patients with neoadjuvant chemoradiation had in 13,5% a critical anastomosis (Grade IV-V) in comparison to 5.3% for the neadjuvant chemotherapy group and 6.2% for the non neoadjuvant group. We investigated the time after the end of chemoradiation and the rate of critical anastomosis using the students t' test. The time between the 6th and 8th postradiation- week was shown to be the optimal time interval for the bronchus healing of the anastomosis (Grade I-II). Patients who were operated before or after the above mentioned time interval had an increased rate of critical bronchus healing (Grade III-IV-V, p:0.003). The postoperative complication rate was 16% after the 42th postradiation day and 34.6% before the 42th postradiation day. Conclusion • A neoadjuvant radiochemotherapy prior to a bronchial sleeve resection impairs the healing of the anastomosis through a high rate of lokal ischemia. • On the contrary to the general recommendation, to perform a lung sleeve resection 4 weeks after radiochemotherapy, our data favours an optimal interval of 6 to 8 weeks. • The neoadjuvant radiochemotherapy raises the complication rate after a bronchial sleeve resection. • Application and dosis of radiation therapy as a neoadjuvant therapy are handled differently. PO-0674 SABR for lung tumors of 5cm or more: can knowledge-based planning detect high-risk treatment plans? S. Van 't Hof 1 , M. Dahele 1 , H. Tekatli 1 , A. Delaney 1 , J. Tol 1 , B.J. Slotman 1 , S. Senan 1 , V. W.F.A.R. 1 1 VU University Medical Center, radiation oncology, Amsterdam, The Netherlands Purpose or Objective There is limited data available on the use of stereotactic ablative radiotherapy (SABR) for lung tumors ≥5cm. We retrospectively assessed high-risk dosimetric features of treatment plans from patients (pt) with SABR-related toxicity after treatment of such tumors, and studied if dose-volume histogram (DVH) predictions of RapidPlan[Varian Medical Systems], a knowledge based planning system, could identify sub-optimal plans in pt with toxicity. Material and Methods We retrospectively analyzed outcomes in 54 pt with primary or recurrent non-small cell lung cancer measuring ≥5 cm, who were treated between 2008-2014 with 5 or 8 fraction SABR using volumetric modulated arc therapy (VMAT). Of these, 15/54(28%) pt had ≥G3 toxicity, most commonly radiation pneumonitis (RP, n=9), fatal lung hemorrhage (LH, n=3) and pleural effusion (n=2). 3/7 pt with interstitial lung disease developed RP. Treatment- related death was considered likely (n=3) or possible (n=8) in 20% of pt. RapidPlan uses a library of different pt plans to generate a model that can be used to identify organs at risk (OARs) which are outliers with respect to the library population. We made a model of all 54 patients and assessed whether pt experiencing toxicity were outliers. A new ‘non-toxicity’ model was then generated that excluded pt with ≥G3 toxicity, and we assessed if this model could identify any sub-optimal plans in the 15 toxicity pt. This was indicated by at least 1 of the clinical DVHs of relevant OAR (CL, ipsilateral lung [IL], proximal bronchial tree [PBT], esophagus or heart) being located above the DVH prediction range generated by the model.

Table 1 : Comparison of segmentation - Similarity measures. Conclusion Inter-observer variability in volume delineation can be reduced with the use of PET modality in radiotherapy planning, guidelines and teaching. Eye movement metrics during contours review could be useful for learning sessions in radiation oncology.

Illustration 1 : Comparison of eye-tracking registrations during segmentation review. Interobservers variability in the identification of anatomical targets and critical structures may explain delineation variability. Greater awareness of this problem, thanks to eye registration ameliorated radiotherapists education. PO-0673 Healing of the bronchial anastomosis and time between neoadjuvant radiochemotherapy and surgery. A. Koryllos 1 , M. Hammer-Helmig 2 , W. Engel-Riedel 3 , D. Zalepugas 1 , E. Stoelben 1 , C. Ludwig 4 1 Krankenhaus Köln-Merheim, Thoracic surgery, Köln- Merheim, Germany 2 Krankenhaus Köln-Merheim, Radiotherapy, Köln- Merheim, Germany 3 Krankenhaus Köln-Merheim, Thoracic oncology, Köln- Merheim, Germany 4 Florence Nightingale Hospital, Thoracic surgery, Düsseldorf, Germany Purpose or Objective Objective of our retrospective study was to evaluate the healing of the bronchial anastomosis in correlation to the time interval between neoadjuvant high dose chemoradiation (>60Gy) and surgery for non-small-cell- We investigated 485 (2006-2014) patients with NSCLC and bronchus-sleeve-lobectomy in our clinic. n:81 patients had neoadjuvant chemoradiation prior to surgery. n:38 patients had only neoadjuvant chemotherapy and n:366 had noch neoadjuvant therapy. Every bronchial anastomosis was assessed bronchoscopically on the 7th postoperative day. The anastomosis healing was divided in 5 different grades: lung cancer patients. Material and Methods