ESTRO 2020 Abstract Book

S538 ESTRO 2020

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 and esophagus was found in 53 (49%), 34 (31%), 15 (14%)

1 Chonnam National University Hwasun Hospital, Radiation Oncology, Hwasun-gun, Korea Republic of

Purpose or Objective Radiation-induced lymphopenia is common during concurrent chemoradiation (CCRT) and is associated with poor outcome. So, we aim to identify the dosimetric parameters in association with lymphopenia. Material and Methods 201 patients with locally advanced stage III NSCLC who received CCRT 60Gy in 30 fractions from 2010 and 2017 were included in this study. All patients received concurrent weekly chemotherapy consisting of paclitaxel first (50 mg/m2 intravenously over 1 hour) and cisplatin (20 mg/m2 intravenously over 1 hour). The median number of cycles of chemotherapy was 5 (range, 1–6). Absolute lymphocyte count (ALC) and absolute neutrophil counts (ANC) were analyzed at pre- and during CCRT. ALC ratio was defined as the ratio of nadir ALC count during CCRT to ALC count pre- CCRT. Pre-CCRT neutrophil–lymphocyte ratio (NLR) was defined as dividing the ANC by the ALC. The associations of the clinical and dosimetric parameters with lymphopenia and treatment outcomes were analyzed. Results Stage IIIA and stage IIIB were 143 (71.1%) and 58 (28.9%), respectively. One hundred and fifty (74.5%) were squamous cell carcinoma with age range of 40 to 75 years (median, 66). The overall survival (OS) and progression- free survival (PFS) of all patients were median 28 months and 12 months, respectively. Age, gross tumor volume (GTV) and lung V30 >16% were significant factors affecting OS on multivariate analysis (Table 1). Pre–CCRT NLR, ALC ratio during CCRT, and mean lung dose (MLD) were associated with PFS on multivariate analysis. Pre–CCRT NLR, ALC ratio, and MLD also were associated with an increased risk of distant metastases. In stepwise multivariate linear regression analysis, GTV and Heart V10 were significantly associated with lymphocyte nadir as a continuous variable. The median PFS stratified by ALC ratio >0.21 and ALC ratio ≤0.21 was 13 months and 8 months, respectively. On univariate logistic analysis, many variables showed to be significantly associated with the development of ALC ratio ≤0.21, including GTV, MLD, Lung V5, Lung V10, Lung V20, Lung V30, mean heart dose, heart V5, heart V10, heart V20, heart V30, and heart V40. The multivariate logistic regression analysis revealed that GTV ( p = 0.008) and heart V20 ( p = 0.001) were the most significant predictors of ALC ratio ≤0.21.

Conclusion This study shows that RT-induced lymphopenia is associated with worse patient outcomes in locally advanced NSCLC patients undergoing CCRT. GTV and heart V20 were significantly associated with ALC reduction ratio.