Abstract Book

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ESTRO 37

impaired pulmonary function, which was defined as forced expiratory volume in one second (FEV1.0) < 1000ml or forced expiratory volume in 1 second as percent of FVC (FEV1.0%) < 50% in this study, were retrospectively analyzed. Toxicities were evaluated using CTCAE v4.0. Results Fourteen patients were identified as severe pulmonary dysfunction. Of 14 patients, twelve of primary lung cancer and two of solitary metastatic lung tumor, FEV1.0 ranged 560 -1310ml, and FEV1.0% ranged 31 -46%. They were treated with CIRT of 54-60 Gy (RBE) in four fractions. Median follow up was 13 months (3.3 – 16.5 months). Two patients started home oxygen therapy after CIRT. One was considered because of chronic obstructive pulmonary disease progression and the other, who had undergone right pneumonectomy and left upper segmentectomy, was temporary started oxygen therapy after the event of pulmonary infection. Grade 3 or more adverse event, including dermatitis, esophagitis and pneumonitis, was not observed. Changes of performance status were not observed before and after treatment. As for local control, only one case of primary lung cancer developed local recurrence 11months after CIRT. Conclusion CIRT was well tolerated in a patient with severe pulmonary dysfunction and also possesses the possibility of curative treatment. EP-1386 Impact of the stereotactic irradiation schedule for non-small-cell lung carcinoma stage I L. Duvergé 1 , P. Bondiau 2 , J. Bellec 1 , R. Corre 3 , C. Ricordel 3 , B. De Latour 4 , J. Doyen 2 , R. De Crevoisier 1 , E. Chajon 1 , J. Castelli 1 1 Centre Eugène Marquis, radiotherapy, Rennes CEDEX, France 2 Centre Antoine Lacassagne, Radiotherapy, Nice, France 3 Centre Hospitalier Universitaire, Pneumology, Rennes, France 4 Centre Hospitalier Universitaire, Thoracic surgery, Rennes, France Purpose or Objective The objectives of the study were to determine the impact on local control and overall survival of a continuous versus discontinuous irradiation (1 day out of 2) in case of stereotactic irradiation (SBRT) in a non-small cell lung carcinoma (NSCLC) stage I. Material and Methods 198 consecutive patients treated in 2 centers between January 2007 and September 2016 by SBRT for a stage I NSCLC were retrospectively included. The prescribed dose ranged from 48 to 60 Gy in 3 to 6 fractions (median BED = 150 Gy). Treatments were delivered on a standard LINAC (Elekta Synergy or Versa HD) or a robotic radiosurgery system (Accuray Cyberknife) using a respiratory correlated image guidance. Based on the ratio between the duration of treatment and the number of fractions, patients were divided into 2 groups: continuous (ratio <2) or discontinuous (ratio ≥ 2). Overall survival (OS), local control (LC) and toxicity data were collected. Results The median follow-up of the cohort was 34 months. The median age was 73 years old. 158 patients were treated according to the continuous schedule and 40 according to the discontinuous schedule. The two groups were comparable on the main confounding factors (age, T stage, gender, histology). No clinical or treatment- related parameters were correlated with local control. The 2-year LC was 100% for the discontinuous group) versus 91% for the continuous group (p = 0.13). Regarding overall survival, the irradiation schedule and age were the only significant parameters in multivariate analysis. The 2-year OS for patients treated with discontinuous schedule was 77% compared to 65% for continuous

schedule (p = 0.035). For the population under 73 years old, 2-year OS for patients treated with discontinuous schedule was 100% compared to 72% for continuous schedule (p = 0.029) while no significant difference was found for the group upper 73 years old (fugure 1). There was less than 3% of acute grade 3 pulmonary toxicity for both groups.

Figure 1: Overall survival according to irradiation schedule and age Conclusion No significant impact of the irradiation scheme was found for LC and acute toxicity. However, patients under 73 years old treated with the discontinuous schedule had a significant increase of OS. This result in favor of discontinuous scheme could be explained either by a lower toxicity or a better LC (tendency but not significant). Supplementary studies are warranted to confirm this findings and identify subgroups who could benefit from a discontinuous schedule of irradiation. EP-1387 High local control with 4D-IGRT based SBRT for stage I NSCLC: a retrospective study. S. Badellino 1 , J. Di Muzio 1 , A. Filippi 2 , A. Guarneri 1 , R. Ragona 1 , U. Ricardi 1 1 University of Torino, Radiation Oncology, Torino, Italy 2 San Luigi Gonzaga Hospital- University of Torino, Radiation Oncology, Orbassano, Italy Purpose or Objective To present Local Control (LC), Metastasis Free Survival (MFS) and Cancer Specific Survival (CSS) rates after Stereotactic Body Radiation Therapy (SBRT) with IGRT technique and small ITV-PTV margin (3 mm) for stage I Non Small Cell Lung Cancer. Material and Methods We retrospectively analyzed a cohort of two-hundred and two consecutive patients treated in a single Institution in the time interval 2010-2015. Patients were planned with frameless approach on 4D-CT scan, and PTV was generated from patients’ specific ITV adding only 3 mm isotropic margin; planning consisted of single arc VMAT delivered with daily cone-beam-CT guidance and a prescription BED 10Gy (at 80%) ranging from 75 to 150 Gy, in consecutive fractions. Results One-hundred fifty (74.25%) male and fifty two (25.75%) female with a median age of 78 years were included; 4 patients were lost at follow-up. 139 (68.8%) patients had a Stage IA NSCLC and 63 (31.2%) Stage IB, respectively; biopsy was performed in 105 (51.98%) of patients. With a median follow-up interval of 30.6 months, actuarial local control (LC) at 12 and 36 months was 96.7% and 84%, respectively (Figure 1). Metastasis-free survival (MFS) at 12 and 36 months was 86.1% and 70.5%, respectively, and Cancer Specific Survival (CSS) at 12 and 36 months was 96.5% and 80.7%, respectively (Figure 1). Median time to local recurrence was 24.7 months. At multivariate analysis, the only significant factor associated to outcome was age (patients older than 78 years had