ESTRO 2020 Abstract book

S584 ESTRO 2020

and esophagus was found in 53 (49%), 34 (31%), 15 (14%) and 6 (6%) tumors, respectively. Primary or metastatic NSCLC (n=73, 68%) and colorectal cancer (CCR; n=14, 13%) were the most represented primary tumors. Median prescription dose was 60 (36-70) Gy in 8 (5-10) fractions, corresponding to a median Biologic Effective Dose (BED) of 105 (48-140) Gy 10 . Median follow-up was 17 (range 3-78) months. At univariate analysis, male gender (p=0.04), non-colorectal origin (p=0.04) and BED >75 Gy 10 (p=0.016) were significantly correlated to increased local control : however only BED >75 Gy 10 proved significant at multivariate analysis (p=0.025, HR: 0.31 [CI95% 0.11-0.86]. Overall toxicity incidence was 30% (31/106), consisting of Grade ≥3 toxicities in 6% (7/106) patients; one (1%) possible treatment-related death, due to severe esophagitis was recorded. Toxicities are outlined in Table 1. At statistical analysis, neither clinical nor treatment- related variable was correlated to occurrence of overall or grade ≥3 toxicity.

PO-1009 Salvage Re-irradiation for Recurrent Lung Cancer: Treatment outcomes and toxicity analysis D.Y. Kim 1 , H.J. Kim 1 , H. Wu 1,2,3 1 Seoul National University College of Medicine, Radiation oncology, Seoul, Korea Republic of ; 2 Seoul National University, Institute of Radiation Medicine- Medical Research Center, Seoul, Korea Republic of ; 3 Seoul National University, Cancer Research Institute, Seoul, Korea Republic of Purpose or Objective Re-irradiation (re-RT) has been increasingly used in patients with recurrent lung cancer for salvage aim, but efficacy and toxicities are not well known. We reported clinical outcomes for patients treated with re-RT and also analyzed risk factors for re-RT-induced toxicities. Material and Methods A total of 79 patients who underwent thoracic salvage re- RT for recurrent lung cancer were retrospectively reviewed. Toxicities were graded according to CTCAE version 5.0. Results Median follow-up time was 23.2 months and median interval time to re-RT was 22.9 months. Overall survival (OS) and loco-regional free survival (LRFS) at 6 month/1 year were 88.6%/75.2% and 97.3%/84.4%, respectively. In multivariate analyses, patients with intrapulmonary + mediastinal recurrence or conventional fractionated re-RT had significantly poor prognosis. There were 7.6% of grade 3 or higher pneumonitis. One patient with grade 5 pneumonitis had idiopathic pulmonary fibrosis (IPF). The factors affecting severe RT pneumonitis were re-RT internal target volume (ITV) ≥ 28 cc and concurrent chemotherapy (CT) with re-RT. Conclusion Re-RT could be considered an effective and feasible treatment option for recurrent lung cancer with an acceptable rate of toxicities, especially in patients without mediastinal lymph node recurrence. ITV volume ≥ 28cc and concurrent CT with re-RT are risk factors for severe RT pneumonitis, and re-RT should be considered with caution for this patient group. PO-1010 Stereotactic Body Radiation Therapy is safe and effective for ultracentral lung lesions D. Franceschini 1 , M. Loi 1 , F. De Rose 1 , C. Franzese 1 , D. Giuseppe 1 , P. Navarria 1 , P. Mancosu 1 , S. Tomatis 1 , M. Scorsetti 1 1 Humanitas Research Hospital, RADIOTHERAPY AND RADIOSURGERY, Rozzano Milan, Italy Purpose or Objective Stereotactic Body Radiotherapy in ultra-central (UC) lung tumors, defined in presence of planning target volume (PTV) overlap or direct tumor abutment to central airways or esophagus, may correlate to higher incidence of severe adverse events. The aim of our study is to evaluate local control rate and toxicity incidence in patients receiving SBRT for UC tumors at our institution. Material and Methods Data from patients treated with SBRT for UC primary and secondary lung tumors between 2013 and 2019 were retrospectively reviewed. Local control (LC) at 1 and 2 years was calculated using the Kaplan-Meier method. Incidence of toxicity was reported and scored with the Common Terminology Criteria for Adverse Events (CTCAE) v.4.03. Univariate and multivariate analysis was performed to assess the impact of clinical and treatment- related variables on LC and toxicity occurrence Results One hundred-six patients met the inclusion criteria, accounting for 108 UC tumors. PTV overlap with trachea/stem bronchi, lobar bronchi, I sublobar division

Bronchial Stricture

Radiation Pneumonitis Hemoptysis Radiation Esophagitis

1 10 (9%) 2 7 (6%) 3 2 (2%)

1 (1%) 2 (2%) 3 (3%)

1 (1%) 3 (3%)

0 0

0 0

1 (%)

4 0 5 0

0 0

0 0

1 (1%)

Conclusion SBRT may achieve high local control rates in patients affected by UC lung tumors if sufficiently dose-intensive schedules are administered. Overall toxicity is acceptable though rare but potentially fatal toxicities may occur irrespectively of delivered dose regimen. PO-1011 Impact of radiation therapy on immunotherapy efficacy in metastatic non-small cell lung cancer. M. Darrason 1 , E. Rivin del Campo 2 , F. Huguet 2 , M. Nguenang 3 , J. Cadranel 4 , V. Fallet 4 1 Tenon University Hospital, Pulmonology, Paris, France ; 2 Tenon University Hospital- Sorbonne University, Radiation Oncology, Paris, France ; 3 Bichat University Hospital, Pulmonology, Paris, France ; 4 Tenon University Hospital- Sorbonne University, Pulmonology, Paris, France Purpose or Objective Recent studies suggest that radiation therapy (RT) enhances anti-tumor immune response. The aim of this study was to determine the impact of previous or concurrent RT on the efficacy of immunotherapy in metastatic non-small cell lung cancers (NSCLC). Material and Methods