Abstract Book

S749

ESTRO 37

metastasis in 25 (16.9%), being the main site of relapse. The time to local failure, regional failure and metastases were 1,3±0,6 years, 1,2±0,6 years and 1,2±1,2 years, respectively. 84 patients (56.8%) are alive without disease and 19 (12.8%) are alive with disease, 11 patients (7.4%) have died from tumor and the rest died from other causes. Mean overall survival was 4.33 ± 0.2 years (95% CI 3.93-4.72). 3.9 ± 0.21 years (95% CI 3,479-4,329).

Using the same dose scheme with VMAT possible advantages are higher conformality in regions with medium and high dose. Therefore the question arise compared “Target Splitting” does the use of VMAT result in higher toxicity? Material and Methods At the most of 7days after two cycles of chemotherapy radiotherapy is initiated by application of following doses: primary tumor 73.8 Gy up to 90 Gy (with positive correlation to the tumor volume), macroscopically affected lymph nodes (LN) 61.2 Gy, elective LN 45 Gy (approximately 6 cm cranial from last macroscopically affected LN). Fractionation: 1.8 Gy twice a day, with an interval of at least 8 hours. Margins GTV (ITV) -> PTV: 7 mm. IGRT is made with a cone beam CT before each fraction and matched to the primary tumor. All patients received the prescribed dose according to the protocol. Acute toxicity was evaluated according to CTCAE 4.03. Results 31 patients with histologically proven locally advanced NSCLC were treated from 01/2015 to 06/2017 (4/6/16/5 patients with stadia IIB/IIIA/IIIB/IIIC , 8th edition UICC). 29 % of the patients had weight loss of > 5% three months before diagnosis, and 23 % had a Karnofsky performance score of < 80 % at start of therapy. Pulmonary V20 on both sides 27 % (median, range 4 – 53 %), V5 on both sides 48 % (median, 14 – 99 %), Dmean 14 Gy (3.8 – 26 Gy). In 7/31 cases (23 %) the QUANTEC constraints V20 (35 %) and in 2/31 cases (6 %) the Dmean (23 Gy) could not be respected. Median follow-up of all patients was 9.3 months (range 2.3 – 29.9). Acute side effects (up to 6 months post RT): pulmonary grade 1/2/3 in 1/4/1 cases; esophageal grade 1/2/3 in 8/18/1 cases; no grade 4/5 toxicities. Late side effects (> 6 months post RT): one therapy- related lethal hemorrhage cannot be excluded. Apart from that no late toxicities > grade 1 were observed so far. One year survival rate 74 %, median survival duration is not yet reached. Local-/regional tumor control rate after one year: 88/85 %. Conclusion 91 % of all patients with locally advanced NSCLC were treated according to the DART-bid protocol with VMAT. Despite application of high doses acute toxicity is low to moderate. A longer observation period is necessary for meaningful statements on late toxicity and overall survival. So far VMAT does not increase toxicity compared Target splitting technique and improves the ability of implementing DART-bid concept (sparing of the ipsilateral lung, narrow margins) for a wide range of patients. EP-1373 Role and Timing of Radiotherapy for Limited- Disease Small Cell Lung Cancer M. Koh 1 , S.Y. Song 1 , S.S. Kim 1 , J.H. Kim 1 , S.D. Ahn 1 , S.W. Lee 1 , S.M. Yoon 1 , Y.S. Kim 1 , J.H. Park 1 , J.H. Jung 1 , E.K. Choi 1 1 Asan Medical Center, Radiation Oncology, seoul, Korea Republic of Purpose or Objective To evaluate clinical outcomes of chest chemoradio- therapy (CRT) in different treatment sequence and to assess the adequacy of current radiotherapy (RT) dose for local tumor control in limited-disease (LD) small cell lung cancer (SCLC). Material and Methods We retrospectively analyzed the patients with LD-SCLC who underwent RT as curative aim at single institution from January 2004 to December 2015. Median radiotherapy dose was 52.5 Gy for 25 fractions.

Conclusion SBRT is a safe and effective treatment for patients with early stage of lung cancer inoperable or who refuse surgery. To improve the control it is necessary to give a dose with BED > 100 Gy. EP-1372 DART-bid with VMAT for locally advanced NSCLC R. Pinter 1 , K. Wurstbauer 1 , M. Kazil 1 , M. Meinschad 2 , P. Cerkl 3 , T. Künzler 2 , P. Clemens 1 , A. De Vries 1 1 Landeskrankenhaus Feldkirch, Radiation Oncology, Feldkirch, Austria 2 Landeskrankenhaus Feldkirch, Medical Physics, Feldkirch, Austria 3 Landeskrankenhaus Hohenems, Pneumology, Hohenems, Austria Purpose or Objective Results of DART-bid treatment (dose-Differentiated Accelerated Radiation Therapy, 1.8 Gy twice a day) with “Target-Splitting” are sufficiently published. Basics are: differentiation of doses, narrow margins, sparing of the ipsilateral lung and following from this exceeding the pulmonary QUANTEC-criteria with a low grade of toxicity.