ESTRO 36 Abstract Book

S349 ESTRO 36 _______________________________________________________________________________________________

Radiation Therapy (SBRT) in 30 Gy single dose, for the treatment of lung lesions. Material and Methods from December 2008 to Decembre 2015 a total of 201 lung lesions in 160 patients affected by lung oligometastatic disease or primary lung cancer were treated at our Institution. All lesions were treated with a 30 Gy single dose SBRT with a stereotactic body frame and a 3-D conformal technique. One-hundred sixty-six (82.5%) lesions were metastases, the remainder were primary lung tumors; main primary tumor sites were lung and colon- rectum (45.2% and 28.8%, respectively). Primary endpoints were local progression-free survival (LPFS) and toxicity, secondary endpoint were disease-free survival (DFS), metastases-free survival (MFS), overall survival (OS) and cancer specific survival (CSS). Results Median LPFS was not reached; 1- and 2-year LPFS were 88.2% and 77.5%, respectively. Overall response rate was 99.5%, complete response (CR) was achieved in 134 (66.6%) lesions, good or partial response in 43 cases (21.3%), stable disease in 23 (11.4%) cases and progression in one case. Local progression occurred in 34 (16.9%) lesions after a median time of 17 months. Volume <20 cc correlated with survival. Median survival time was 40 months (range 28-51 months) and 1- and 2-years OS were 84.7% and 63.9%, respectively. Median CSS was 48 months (range 38-57 months) and 1- and 2-years CSS were 87.1% and 67.6%, respectively. Median DFS and MFS were 16 and 22 months, respectively, while 1- and 2-years DFS and MFS were 64.4% and 43.1% and 67% and 48.5%, respectively. On the multivariate analysis CR was the most important factor significantly associated with improvement and survival. Acute toxicity occurred in 43 (21.3%) cases, with 10 (4.9%) cases of Grade ≥3 toxicity. Late toxicity occurred in 80 (39.8%) lesions and the rate of Grade ≥3 toxicity was 5.9% our study represents, at our knowledge, the largest series in the literature on the use of SBRT 30 Gy single dose for lung lesions. Our results confirm the safety and effectiveness of this schedule, both in primary tumor and metastases, achieving in selected patients, even long- term survival. Single dose SBRT is characterized by high patients’ compliance and it can be easily interfaced with systemic therapies. PO-0667 The differences between two groups of patients with NSCLC depending on the imaging for radiotherapy A. Masarykova 1 , D. Scepanovic 1 , P. Bires 1 , D. Lederleitner 1 , M. Pobijakova 1 , P. Povinec 2 1 National Cancer Institute, Radiation Oncology, Bratislava, Slovakia 2 BIONT PET Center, Nuclear Medicine, Bratislava, Slovakia Purpose or Objective Background. – The target volumes of lung cancer are underestimated on a standard three-dimensional positron emission tomography/computed tomography (3D PET/CT) scan when compared to target volumes defined on respiratory gated or four-dimensional (4D) imaging. 4D methods strive to achieve highly conformal radiotherapy for lung tumours, in the presence of respiratory-induced motion of tumours and normal tissues. Purpose. - The differences between two groups of patients with non small cell lung cancer depending on the imaging for simulation of radiotherapy (3D vs 4D PET/CT), were examined. Material and Methods A total of 58 patients with NSCLC (45 male and 13 female) underwent an FDG-PET/CT for radiotherapy planning purposes. There were 26 patients who performed 3D PET/CT from 2011 to 2013 and 32 patients had 4D PET/CT (12 lesions). Conclusion

from 2014 to 2016 for the radiotherapy planning. Median age was 63 (range, 49-89). All patients (58) had locally advanced stage of NSCLC. Sixteen percent of patients had atelectasis and 60% mediastinal lymph nodes. Squamous cell lung cancer has been the most represented (72% patients), a remnant was adenocarcinoma. All patients were treated with radical radiotherapy. Dose prescription ranged from 56 to 70.2Gy. Forty eight patients have received chemotherapy sequentially. Results A comparison of the 3D and 4D volumes has shown that the 4D GTV was on average 58% smaller than the 3D GTV (p < 0.01). The 10 mm 4D planning target volume (PTV) was on average 28% smaller than the 10 mm 3D PTV (p < 0.01). There was not statistically significant difference between two groups of patients regarding the rate of local recurrence (p=0.3188). However, regarding the rate of distant metastases there was statistically significant difference in favour of the 3D imaging group (p=0.0455). Seven patients in 3D imaging group and 9 from 4D imaging group lived at the time of analysis. One year disease free survival (DFS) was 42% for 3D imaging group and 37% for 4D imaging group (p=0.7903). Also, there was not statistically significant difference regarding 1 year overall survival (OS) between these two groups of patients (3D=69% and 4D=50%, p=0.1834). Conclusion 4D PET/CT is clinically a feasible method, to correct respiratory motions in the thorax. Our analysis showed that the definition of GTV and PTV are better in 4D imaging group. However, there was not differences between two groups of our patients regarding local control, as well as DFS and OS. PO-0668 Five-fraction SBRT for central NSCLC in-field recurrences following high-dose conventional radiation M.C. Repka 1 , N. Aghdam 1 , S. Kataria 1 , S. Suy 1 , E. Anderson 2 , S.P. Collins 1 , B.T. Collins 1 , J.W. Lischalk 1 1 Georgetown University Hospital, Department of Radiation Medicine, Washington, USA 2 Georgetown University Hospital, Division of Pulmonary and Critical Care Medicine, Washington, USA Purpose or Objective Local treatment options for patients with in-field non- small cell lung cancer (NSCLC) recurrence following conventionally fractionated external beam radiation therapy (CF-EBRT) are limited. Stereotactic body radiation therapy (SBRT) is a promising modality to achieve local control, although toxicity remains a concern. We report our experience using this novel technique. Material and Methods Patients previously treated with high-dose CF-EBRT (≥59.4 Gy, ≤3 Gy/fraction) for non-metastatic NSCLC who underwent salvage SBRT for localized hilar or mediastinal in-field recurrence were included in this analysis. Total SBRT dose was stratified as low (<40 Gy) or high (≥40 Gy). The Kaplan-Meier method was used to estimate local control and overall survival. Durable local control was defined as ≥12 months. Toxicity was scored per the CTC- AE v4.0. Results Between November 2004 and August 2014, twenty patients were treated with five-fraction robotic SBRT for central in-field recurrence following CF-EBRT. Twelve recurrences were identified within the mediastinum, and eight were identified within the hilum. One-half of recurrences were adenocarcinoma, while 35% of tumors were classified as squamous cell carcinoma. The median interval between the end of CF-EBRT and SBRT was 23.3 months (range: 2.6 - 93.6 months). The median CF-EBRT dose was 63 Gy (range: 59.4 - 75 Gy), the median SBRT dose was 35 Gy (range: 25 - 45 Gy), and the median total equivalent dose in 2 Gy fractions (EQD2) was 116 Gy (range: 91.3 - 136.7 Gy). At a median follow-up of 12 months for all patients