ESTRO 38 Abstract book

S754 ESTRO 38

median PTV was 91.86 cc (53.2-165.9). Median prescribed dose was 40 Gy (35-55) and 35 Gy (35-45) in 5 fractions to T and N, respectively. At the first follow up, all (100%) pts had a metabolic response at PET-CT. After a median follow-up of 7 months (range, 4-41) there were 3 (18%) local recurrences (LR), 2(12%) regional node (RN) recurrences and 1(6%) distant progression (DP). Median LR- free survival (FS), RN-FS and DP-FS were 6 (2-41), 7 (2-41) and 7 months (2-41), respectively. Median overall and cancer specific survival were 7 months (2-41). Of note, 2 pts who had hemoptysis before SBRT resolved the symptom after treatment. No patients developed > grade 2CTCAE toxicity. Conclusion SBRT was a feasible,safe and effective treatment in selected unresectable LA-NSCLC pts. Although preliminary outcomes were promising in terms of results and toxicity,larger and more mature studies are needed before the routinely use in clinical practice. EP-1382 Texture analysis of FDG-PET in NSCLC treated with SBRT:a validation study of two prognostic features M. Bertolini 1 , M. Galaverni 2 , M. Manicone 2 , I. Renna 2 , P. Ciammella 2 , L. Giaccherini 2 , F. Bellafiore 2 , G. Timon 2 , F. Vigo 2 , A. Rosca 2 , D. Ramundo 2 , M. Galeandro 2 , M.P. Ruggieri 2 , T. Palmieri 2 , A. Botti 1 , M. Orlandi 1 , R. Sghedoni 1 , E. Cagni 1 , E. Grassi 1 , F. Fioroni 1 , A. Filice 3 , M. Casali 3 , M. Iori 1 , C. Iotti 2 1 Azienda USL-IRCCS di Reggio Emilia, Medical Physics Unit, Reggio Emilia, Italy ; 2 Azienda USL-IRCCS di Reggio Emilia, Radiation Oncology Unit, Reggio Emilia, Italy ; 3 Azienda USL-IRCCS di Reggio Emilia, Nuclear Medicine Unit, Reggio Emilia, Italy Purpose or Objective To validate the prognostic value of two textural features of 18F-FDG PET/CT in SBRT-treated early-stage NSCLC Material and Methods HISTO_Kurtosis and Long-Run Low Gray-level Emphasis (GLRLM_LRLGE) are textural features that predicted recurrence free survival (RFS) in a previous analysis on 18F-FDG PET/CT of patients with early stage NSCLC treated with SBRT at our center. We validated this findings in a wider patient population. Twenty-six patients with early stage NSCLC between 2010 and 2017 underwent a 18F-FDG PET/CT before SBRT treatment. In PET image sets of every patient a volume of interest was defined around the tumor by two experienced radiation oncologists. An automatic segmentation was performed inside this volume by using a fixed threshold of 40% of maximum SUV (standardized uptake value). For each volume 45 textural features were calculated using LIFEx software. For each patient clinical data about age, gender, Karnofsky Performance Status (KPS), initial stage, histology, location, prescribed biological effective dose, local recurrence, lobar recurrence, regional recurrence, distant recurrence and death were acquired. Study endpoint was recurrence free survival (RFS). Cut-off values were obtained using a support vector machine (SVM) based analysis and RFS were compared using log- rank test analysis. Results Median age of the population was 75 years (range 53-90) with 19 men and 7 women. The majority of patients (22) had KPS ≥ 80. Stage was T1N0M0 in 10 patients, T2N0M0 in 11, T3N0M0 in 5. Pathological diagnosis was achieved in 15 patients (7 adenocarcinomas and 8 squamous cell carcinomas). Tumor was located in upper lung field in 11 patients, in middle in 1 and in lower in 14. Most of the patients (20) were treated with BED ≥ 100 Gy, calculated using linear quadratic model with an α/β ratio of 10 Gy. The median follow-up period was 17.5 months for the entire population and 20 months for the surviving patients. 1-year OS was 69% (CI 64-74). At final follow-up, 13

Intra- Fraction CBCT

Vertical (cm)

Lateral (cm)

Longitudinal (cm)

4D-CT (51)

0.07±0.07 0.10±0.08

0.10±0.09

Mean

Maximum 0.3

0.35

0.29

DIBH-CT (25)

0.11±0.08 0.14±0.09

0.10±0.09

Mean

Maximum -0.23

-0.29

0.4

Conclusion When the intra-fraction deviation amounts in 76 fractions were examined by 4D-CT and DIBH-CT techniques, it was determined that treatment could be performed reliably with ITV 3 mm safety margin in both IGRT techniques. In case of maximum deviation of ± 2 mm during treatment;  With 4D-CT, safe treatment can be performed in 96.1% of all fractions in the lateral direction, in 90.2% of all fractions in the longitudinal direction, and in 90.16% of all fractions in the vertical direction. With DIBH-CT, safe treatment can be performed in 84% of all fractions in the lateral direction, in 76% of all fractions in the longitudinal direction, and in 92% of all fractions in the vertical direction. Movement management was provided by DIBH-CT and 4D- CT techniques. However, there may be intra-fractional movement in the tumor. PTV should be created by adding 3-5mm safety margin to ITV. EP-1381 Stereotactic Body Radiotherapy for Unresectable Locally-Advanced Non Small Cell Lung Cancer F. Arcidiacono 1 , M. Casale 1 , P. Anselmo 1 , F. Trippa 1 , L. Draghini 1 , S. Terenzi 1 , A. Di Marzo 1 , M. Italiani 1 , S. Fabiani 1 , E. Maranzano 1 1 Radiotherapy Oncology Centre, Santa Maria Hospital, Terni, Italy Purpose or Objective Conventional fractionated radiotherapy (cRT) concurrent with chemotherapy (ChT) is the standard of care in unresectable locally-advanced non small cell lung cancer (LA-NSCLC).The majority of patients (pts) cannot tolerate this treatment due to its toxicity, so sequential ChT followed by cRT is the more frequent choice in clinical practice. Recently, stereotactic body radiotherapy (SBRT) has been used instead of cRT in early-stage NSCLC offering superior control with less toxicity. Few studies exist on SBRT in LA-NSCLC. We present our experience on this last topic. Material and Methods Between June 2015 and July 2018, 17 LA-NSCLC pts who underwent SBRT were analyzed . 13/17 (76%) pts received neoadjuvant ChT before SBRT. All pts had CT-PET before SBRT. In pts submitted to neoadjuvant ChT the target volume was the residual disease defined on the basis of CT-PET images.A specific treatment planning for primary tumor (T) and lymph-node/s (N) was donein9(53%) pts, while in remaining 8(47%) the planning target volume (PTV) included both T and N. All pts repeated CT-PET 3 months after treatment and thereafter every 4-6 months. Response, cancer specific survival and toxicity were evaluated. Results Median age was 72 years (55-81). At diagnosis, 8(47%), 7(42%) and 2(11%) pts had clinical N1, N2 and N3, respectively. Primary tumor was central in 12(71%) and peripheral in 5(29%) pts. Median PTV for T and N separately treated were 17.2 cc (8.7-67.96) and 15.02cc (9.9-72.3), while for T and N treated in the same target 