Abstract Book

S747

ESTRO 37

concomitant or sequential radio-chemotherapy with radical intention. DVH’s were generated and the following data for lung as organ at risk (lung OAR) were collected: V 5 , V 20 and mean lung dose (MLD). The healthy lung ((left lung + right lung)-PTV) was considered the lung OAR. Toxicity was assessed by Common Terminology Criteria for Adverse Events (CTCAE) v4.0 scoring system. Results Patient description and dose volume data are summarized in Tables 1 and 2.

institution except for 6 patients (5.3%). 1 patient (0.9%) had MLD>21 Gy and 5 patients (4.4%) had V 20 >35%. In 31 patients (27.2%) was not possible to achieve V5<65% and in 42 patients (36.8%) V5 was larger than 60%. For those patients who hadn’t met one constraint, the other two were achieved. With a median follow-up of 4 months (range:1–32), one case (0.9%) of RP grade 2 and six cases (5.3%) of RP grade 3 have been identified. No cases of RP grade>3. 53 patients (46.5%) died from other causes. 4 patients with RP grade 3 didn't met the V5<65% constraint: 3 were treated with 60Gy/30s (2 with concomitant chemotherapy and 1 sequential) and 1 with 66Gy/33s RT alone. V5 values were respectively 66.3%, 68.4%, 73.6% and 77.4%. The other two patients with RP grade 3 met V5<65%: one was treated with 60Gy/30s and sequential chemotherapy and one with 66Gy/33s and RT alone. The patient with the largest PTV volume (1507.7 cm 3 ), treated with 60Gy/30s and concomitant chemotherapy, didn't met V5<65% and had RP grade 3. No patient treated with 70Gy/35s developed RP. Conclusion Our degree of compliance with the restriction V5<65% is not entirely satisfactory. The follow up time is still short for some patients but treatments have resulted in low incidence of RP grade 3 (4.4%). Nevertheless 53 patients have died from other causes. Further analysis of late toxicity with longer time of follow-up should be done and efforts are needed to reduce these values by probably implementing new techniques such as respiratory motion management. EP-1369 High local control for lung SBRT of comorbid patients: prospective monocenter phase II STRIPE trial S. Adebahr 1,2,3 , U. Nestle 1,4 , K. Kaier 5 , T. Schimek-Jasch 1 , E. Gkika 1 , F. Momm 6 , G. Becker 7 , A.L. Grosu 1,2,3 1 Medical Center- Faculty of Medicine- University of Freiburg, Department of Radiation Oncology, Freiburg, Germany 2 German Cancer Consortium DKTK, Partner Site Freiburg, Freiburg, Germany 3 German Cancer Research Center, DKFZ, Heidelberg, Germany 4 Kliniken Maria Hilf GmbH Mönchengladbach, Department of Radiation Oncology, Mönchengladbach, Germany 5 Faculty of Medicine and Medical Center - University of Freiburg, Institute of Medical Biometry and Statistics, Freiburg, Germany 6 Ortenau Klinikum Offenburg-Gengenbach, Department of Radio-oncology, Offenburg, Germany 7 Medical Center- Faculty of Medicine- University of Freiburg, Clinic for Palliative Care, Freiburg, Germany Purpose or Objective To investigate efficiency and safety of pulmonary moderate-dose SBRT in elderly and comorbid patients. Material and Methods Elderly or comorbid patients with pulmonary lesion <= 5cm (early stage NSCLC or ≤ 2 pulmonary metastases of a controlled primary tumor) were treated with 4DPET/CT- based SBRT (3x12.5 Gy or 5X 7Gy to 60% isodose) within the prospective, monocenter phase II STRIPE trial, funded by Deutsche Krebshilfe. Follow up was performed at 2 and 7 weeks, then 3-monthly until 2 years after SBRT, including toxicity, quality of life (QoL) and CT assessment, PET/CT in case of suspected progression. Predefined prognostic factors were analyzed. Results From 02/2011 to 11/2014 100 eligible patients (63% male, 27% female, mean age 70.3 years, mean Charlson Comorbidity Score 6.3) were treated for 56 NSCLC and 44 metastases. Tumors were located centrally (27%) or peripherally (73%). Local control rate after 2 years was

90 patients (79.0%) received a dose of 60 Gy in 30 sessions, 17 patients (14.9%) 66 Gy in 33 sessions and 7 patients (6.1%) 70 Gy in 35 sessions. Mean PTV volume was 474.1cm 3 . Mean values for lung OAR were: volume 3700.6 cm 3 , MLD 13.9 Gy (range:13.6- 21.0), V 5 55.7% (range:12.2-81.8) and V 20 23.7% (range:5.1-38.2). All values matched the lung OAR dose constraints of V 20 <35% and MLD<20 Gy that are being applied in our