ESTRO 36 Abstract Book

S655 ESTRO 36 _______________________________________________________________________________________________

EP-1212 Parenchymal and functional lung changes after stereotactic body radiotherapy for early-stage NSCLC J. Rieber 1 , J. Dern 1 , D. Bernhardt 1 , L. König 1 , S. Adeberg 1 , A. Paul 1 , J. Kappes 2 , H. Hoffmann 3 , J. Debus 1 , C.P. Heussel 4 , S. Rieken 1 1 University Hospital Heidelberg, Radiooncology, Heidelberg, Germany 2 Thoraxklinik- University Hospital Heidelberg, Pneumology, Heidelberg, Germany 3 Thoraxklinik- University Hospital Heidelberg, Thoracic Surgery, Heidelberg, Germany 4 Thoraxklinik- University Hospital Heidelberg, Diagnostic and Interventional Radiology, Heidelberg, Germany Purpose or Objective Stereotactic body radiotherapy (SBRT) has been increasingly used for patients with early-stage non-small cell lung cancer (NSCLC) who are classified medically inoperable due to severe pulmonary comorbidities. However, main toxicity following SBRT is detected in the already impaired lung tissue in this patient group and might further influence quality of life and survival. Material and Methods Parenchymal and functional lung changes were evaluated in 70 patients with early-stage NSCLC treated with SBRT between February 2004 and May 2015 at the University Hospital Heidelberg and for whom more than one year of CT follow-up scans were available. In total, 393 CT scans were examined. Incidence, morphology and severity of lung abnormalities as well as pulmonary function changes were analyzed and correlated with outcome. Results Median follow- up time was 28.6 months with 2- year and 3-year overall survival (OS) of 75.5% and 54.1% and 2-year and 3-year local progression-free survival (LPFS) of 88.4% and 79.9%. Regarding acute parenchymal lung changes within the first 6 months after SBRT, 10% of the cases showed no increased density, while 11% were classified as patchy ground-glass opacity, 25% diffuse ground-glass opacity, 25% patchy consolidation and 29% diffuse consolidation. Late CT changes after 6 months were detected in all patients with 10% scar-like fibrosis, 7% mass-like fibrosis and a modified conventional pattern of fibrosis in 83% of the patients. In general, most patients only suffered from mild to moderate CT abnormalities. Maximum severity score for parenchymal changes was significantly associated with ipsilateral lung dose in biological effective dose (BED) (p=0.014) and PTV size (p<0.001), but not with any further investigated risk factor. Furthermore, patients with no or mild parenchymal lung changes showed significantly improved 2-year and 3-year OS of 79.6% and 61.9%, while moderate to severe changes had 1-year and 3-year OS of 40% and 30%, respectively (p=0.043). Regarding functional lung changes, baseline lung function was generally poor with mean forced expiratory volume in 1 second (FEV1) of 1.5l (predicted 54.1%), mean total lung capacity (TLC) of 5.7 and forced vital capacity (FVC) of 2.7l. SBRT treatment significantly reduced post-SBRT lung function: TLC (-0.41l; p=0.001); FVC (-0.17l, p<0.001), FEV1 (-0.8l, p<0.001), FEV1% (-28.2%, p<0.001) and air way resistance (+0.1, p=0.003). While pre- and post-treatment lung function parameters did not significantly affect OS (p>0.05), higher absolute reduction in FVC was significantly associated with worse OS (p=0.005). Conclusion SBRT was generally tolerated well with only mild toxicity. However, this is the first study illustrating that both parenchymal and functional lung changes following SBRT might impair survival.

EP-1213 Long-term outcomes of Stereotactic Ablative Radiotherapy for stage I non-small cell lung cancer S. Lee 1 , S.Y. Song 1 , S.S. Kim 1 , S.W. Lee 1 , S.D. Ahn 1 , S.M. Yoon 1 , Y.S. Kim 1 , J.H. Park 1 , J.H. Kim 1 , E.K. Choi 1 1 Asan Medical Center- Univ of Ulsan, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective To investigate long-term clinical outcomes of stereotactic ablative radiotherapy (SABR) in patients with medically inoperable stage I non-small cell lung cancer (NSCLC) Material and Methods A retrospective analysis was performed on a total of 169 patients with 178 lesions, 9 patients with synchronous cancer, of stage I non-small cell lung cancer treated with SABR at a single institution from June 2000 to May 2015. Patients with recurrent lung cancer, another primary malignancy, or prior history of RT to chest were excluded. Dose scheme of SABR was 48 Gy in four fractions in early phase, but was escalated to 60 Gy in four fractions from June 2009. CyberKnife™ was also introduced at June 2011. Patterns of failure and survival were evaluated. All failures were identified during total follow-up period, not as initial presentation. Survival was calculated from the date of initiation of radiotherapy. Toxicity was graded using the Common Terminology Criteria for Adverse Events (CTCAE) version 4.03 except rib fracture. Results Median age was 73 years (range, 40-91). Pathologic diagnosis was done in 173 tumors (97%); Adenocarcinoma in 87 tumors (49%), squamous cell carcinoma in 78 tumors (44%), unspecified NSCLC in 5 tumors (3%) and others in 3 tumors (2%) were identified. There were 39 tumors (22%) with T1a, 70 tumors (39%) were T1b, and 69 tumors (39%) with T2a. Twenty-five (14%) tumors were located at central area. Fractionation schemas were 60 Gy in four fractions (46%), 48 Gy in four fractions (29%), and 54 or 60 Gy in three fractions (16%). Forty-four tumors (25%) were treated with CyberKnife TM . Median follow-up time was 32 months. The 3-and 5-year overall survival rates were 69.5% and 46.7% respectively. The 3-year progression free and cancer-specific survival rates were 62.3% and 86.8%. The 3-year and 5-year actuarial local control rates were 86.3% and 79.3%. Tumor size was an independent prognostic factor for survival. No relapse occurred in tumor ≤ 2cm irrespective of SABR dose. Escalated dose around 60 Gy/4fx (150 Gy 10 ) achieved higher local control compared with 48 Gy/4fx (106 Gy 10 ), 76.2% versus 60.6% at 5-year (p=0.022) in tumors larger than 2cm diameter. However, escalated dose could not reach improved overall survival. Grade 5 toxicities were noticed in two patients; radiation pneumonitis in 1 and fatal hemoptysis in the other patient with centrally- located tumor. Conclusion SABR provides satisfactory long-term local control and overall survival in medically inoperable stage I NSCLC. Relatively lower dose, 48 Gy/4fx, is enough for T1a tumor, but dose escalation to 60 Gy/4fx improves local control for tumor larger than 2cm diameter. EP-1214 Stereotactic Ablative Radiotherapy in Clinical Stage I (<5cm) Non-Small Cell Lung Cancer S.J. Ahn 1 , W. Jeon 1 , Y.C. Kim 2 , I.J. Oh 2 , J.U. Jeong 1 , M.S. Yoon 1 , J.Y. Song 1 , T.K. Nam 1 , W.K. Chung 1 1 Chonnam National University Medical School, Radiation Oncology, Hwasun, Korea Republic of 2 Chonnam National University Medical School, Pulmonology, Hwasun, Korea Republic of