ESTRO 38 Abstract book

S741 ESTRO 38

radiotherapy with 1-5 residual lesions following systemic treatment) lung cancer. Results 91 patients and 99 metastases were included. Local control was 91%, median progression free survival (PFS) was 6.3 months [4 ; 8.1] and median overall survival was 28.2 months [20.1 ; 35.5]. There were significant differences between metastatic settings : median overall survival was not reached in the oligometastatic group, 33 months in the oligorecurrence group, 28.2 months in the oligopersistent group and only 6.5 months in the oligoprogressive group. Metastatic site, nodal status and free interval for oligorecurrent patients were significant prognostic factors. Toxicities were moderate since only 5.5% of patients experienced grade 3 acute toxicities and none had late grade 3-4 toxicity. SBRT allowed delaying the administration of systemic treatments since more than half of the patients could remain free from systemic treatment for several months. Conclusion Optimal dose, fractionation and timing regarding association with systemic treatments remain to be defined. Aggressive metastatic management seamed feasible and appeared to delay reintroduction of systemic treatments. Larger scale randomized studies are necessary to demonstrate survival benefit. EP-1354 Impact of Pulmonary SABR on Pulmonary Function Tests: Report of a single institution experience M. Keys 1 , S. O'Sullivan 1 , R. Mc Dermott 1 , N. Wallace 2 , M. Dunne 1 , J. Armstrong 1 , P. Thirion 1 1 St. Luke's Radiation Oncology Network, Radiation Oncology, Dublin 6, Ireland ; 2 Cork University Hospital, Radiation Oncology, Cork, Ireland Purpose or Objective Pulmonary Stereotactic Body Radiotherapy (SABR) is a well established standard alternative therapy for patients (pts) diagnosed with inoperable early-stage Non Small Cell Lung Cancer (NSCLC). The impact of SABR on pulmonary function remains unclear. Results from retrospective studies suggest a minimal if any decline in post-SABR pulmonary function. The results were also mixed with regard to the Pulmonary FunctionTest (PFTs) parameter effected. We report here a single institution experience comparing prospectively acquired pre and post-SABR PFTs . Material and Methods From March 2014 to May 2018, 84 pts. with documented PFTs pre- and post-SABR (within 1 year post therapy) were identified. The main characteristics of the population included: median age of 75 years (from 59-91years), female predominant (57%), underlying COPD stage 3- 4 (23.8%), and ex- or active smoker (87.6%). All pts. except for one were treated for NSCLC, pathologically proven in 86 pts. The tumour locations were mostly in the upper lobes (58.3%) and peripheral (88.1%). The median GTV and PTV volumes were 11.68cm 3 (from 1.04 to 52.58cm 3) and 33.11cm 3 (from 6.39 to 116.72cm 3) respectively. The protocol driven radiation schedules used were 54Gy/3 (11.9%), 60Gy/5 (73.8%) and 60Gy/8 (14.3%). Paired-samples t-tests were conducted to evaluate the Pre- and post-SABR PFT values and independent samples t-tests and ANOVA were conducted to compare the results between demographic characteristics. Results Pre- and post-SABR FEV 1 data was available for all 84 pts. The median pre- and post-SABR FEV 1 was 1.41L (from 0.4 to 2.9L) and 1.3L (from 0.45 to 2.8L) respectively. Overall There was a statistically significant post-SABR FEV 1 decrease, with a mean decrease of .05L [95% CI: 0.002 to 0.11, p=0.04]. Pre- and post-SABR DLCO was available in 68 pts. The median pre- and post-SABR DLCO was 9.1 ml/mmHg/min (from 0.6 to 20.7) and

9.5ml/mmHg/min (from 1.35 to 26.1) respectively. Overall there was a statistically significant post-SABR DLCO decrease, with a mean decrease of 2.5% [ 95% CI: 0.1-4.89, p=0.04]. However Individual variation was observed with a decrease observed in 40 pts, an increase in 22, and no change in 6. The only identified negative risk factor for post-SABR DLCO reduction was female gender. Conclusion The present study found a statistically significant post- SABR DLCO and FEV 1 decrease, however with significant inter-individual variation. Whether this is a temporary or permanent change, we were unable to assess this. Whether this decrease translates into a functional change is unlikely but not proven. The clinical significance and reversibility need to be further studied through large scale clinical trials and compared to other therapeutic alternatives. EP-1355 Oligo-progressive status exhibits unfavorable survival in pulmonary oligo-recurrence treated by SABR H. Lee 1,2 , J. Tsai 3 , S. Chen 4 , I. Lai 5 , C. Chen 2,6 , C. Ho 7 , J. Chiou 1,2 , Y. Kuo 4 1 Taipei Medical University Hospital- Taipei Medical University, Department of Radiation Oncology, Taipei, Taiwan ; 2 Taipei Medical University, Taipei Cancer Center, Taipei, Taiwan ; 3 Taipei Medical University- Shuang Ho Hospital, Department of Radiation Oncology, New Taipei City, Taiwan ; 4 China Medical University Hospital, Department of Radiation Oncology, Taichung, Taiwan ; 5 Taipei Veterans General Hospital, Division of Radiation Oncology- Department of Oncology, Taipei, Taiwan ; 6 Wan Fang Hospital- Taipei Medical University, Department of Radiation Oncology, Taipei, Taiwan ; 7 Camillians Saint Mary’s Hospital Luodong, Department of Radiation Oncology, Yilan, Taiwan Purpose or Objective Oligo-progression exhibits distinct biological signatures during the evolution of cancer metastasis, but its clinical significance has not been clarified. We investigated the treatment outcome of stereotactic ablative radiotherapy (SABR) for pulmonary oligo-recurrence in metastatic cancer patients with controlled extrapulmonary diseases and evaluated the prognostic value of oligo-progressive status of targeted lung tumors. Material and Methods The patient inclusion criteria were pulmonary oligometastases with controlled primary and extrapulmonary disease, SABR as the primary local treatment for oligo-recurrent lung tumors, and consecutive imaging follow-up. Pulmonary oligo- recurrence was defined as ≤5 metastatic lung tumors with absent or controlled disease elsewhere. The status of targeted lung tumors were further classified into oligo- progressive and controlled status to indicate the drug resistance developing in lung or not, respectively. Overall survival (OS) and prognostic variables were evaluated using Kaplan–Meier analysis and Cox regression model. Results Thirty-two patients with sixty-seven lung tumors treated with SABR were enrolled. With a median follow-up period of 19.5 months, the median OS was 33.0 months. Oligo- progressive status ( P = .0413) and an increased number of lung tumors ( P = .0217) were independently associated with inferior OS. A higher biological effective dose (BED 10 ) ( P = .0423) was independently correlated with longer in- field radiographic progression-free survival. Synchronous metastases ( P = .0133) and an Eastern Cooperative Oncology Group score of ≥1 ( P = .0010) were significantly associated with inferior out-field radiographic progression-free survival. Grade 2 radiation pneumonitis occurred in six (18.8%) patients. No toxicity above grade 2 was recorded.