ESTRO 2020 Abstract book

S579 ESTRO 2020

(dyspnea) according to CTCAE scale v4.0 and no case of G4 or more side effects. About late toxicities, 23% of pts developed a side effect: only one pt had dyspnea G3 and 3 had G3 pneumonitis, no G4 or more were reported. At time of analysis 5 pts were lost at follow up; 41 pts were still alive, 56% did not have evidence of disease and 44% with loco-regional or metastatic disease; 6 pts died after progression and 5 pts for other or unknown causes . During regular follow up 13 pts developed loco-regional progression, while 13 developed contralateral or extra thoracic metastases (six pts had both). Conclusion In selected pts affected by centrally located pulmonary lesions SBRT seems to be feasible and effective representing an efficient treatment. SBRT seems to be well tolerated and associated with relatively low rates of serious treatment related toxicity. More robust clinical data are awaited from on going international clinical trials. PO-1001 Shortened radiation time promotes recovery from lymphopenia in early-stage NSCLC who received SBRT Q. Zhao 1 , Z. Zeng 1 1 Zhongshan Hospital- Fudan University, Department of Radiation Oncology, Shanghai, China Purpose or Objective To evaluate the potential impact of radiation time on radiation-induced lymphopenia (RIL) and subsequent recovery after stereotactic body radiation therapy (SBRT) and to examine the association between these parameters and patient outcomes in early-stage non-small cell lung cancer (NSCLC). Material and Methods Clinical and laboratory records of 115 patients who had received SBRT for early-stage NSCLC were reviewed to assess changes in total lymphocyte counts (TLCs) following SBRT. Post-SBRT TLC values <1,000 cells/µL indicated lymphopenia. Patients that exhibited post-SBRT TLC levels similar to their pre-SBRT levels at least twice during the first 6 months of follow-up were considered to have recovered from RIL and were classified as the lymphocyte recovery (LR) group. Associations of TLC kinetics with clinical and treatment features and outcomes were analyzed. Results Most patients (100/115, 86.96%) experienced significantly decreased median TLCs following SBRT (1,700 vs. 1,100 cells/µL; P <0.001), and 52 patients (45.21%) met the criteria for lymphopenia (Figure 1A). Six months after SBRT, 44 patients (38.26%) had recovered. A negative correlation between TLC reduction and radiation time was observed (r=-0.381, P <0.001) (Figure 1B). According to the receiver-operating characteristic (ROC) curve analysis, the optimal cut-off value for radiation time to predict LR following RIL was 3,950 sec ( P <0.001) (Figure 1C). Multivariate analyses demonstrated that radiation time was significantly associated with LR (odds ratio [OR], 0.113; 95% confidence interval [CI], 0.029–0.432; P =0.001) but not TLC reduction ( P =0.575). LR within 6 months after SBRT was associated with improved progression-free survival (PFS) in patients without lymphopenia ( P =0.034) but had little effect in patients with lymphopenia ( P =0.405) (Figure 2). Conclusion A longer radiation time was associated with a lower rate of LR within 6 months after SBRT in patients with early- stage NSCLC. Given the association of severe and persistent RIL with survival in NSCLC, further study of the effect of radiation time on immune status is warranted. PO-1002 Early outcomes of stereotactic MR-guided adaptive radiation therapy in 54 high-risk lung tumors T. Finazzi 1 , C. Haasbeek 1 , M. Palacios 1 , F. Spoelstra 1 , M. Admiraal 1 , A. Bruynzeel 1 , B. Slotman 1 , F. Lagerwaard 1 , S.

(PFS) and overall survival (OS) as well as correlations with clinic-pathological features investigated. Results Median OS was 14 months (range: 3-167 months). The OS rates at 1- and 2 years were 68% and 20%. Local control rates for the entire cohort at 1 and 2 years were 74% and 61%, respectively. Median PFS and PFS at 1 and 2 years were 13±1.4 months, 58% and 19%. PD-L1 expression <1% on tumor cells was associated with improved OS, PFS and local control in patients treated with concurrent CRT. Univariate analysis showed a trend for improved OS and local control in patients with low CD8+ TILs density (p=0.055; p=0.092). The longest and shortest OS were achieved in patients with type I (PD-L1neg/CD8low) and type IV (PD-L1pos/CD8low) (median OS: 57±37 vs. 10±5months, p=0.05), respectively. In univariate and multivariate analysis for OS, TIME subgroups had significant differences (p=0.05; p=0.048) as well as in univariate analysis for PFS and local control (p=0.05; p=0.035). Conclusion The classification of tumors into four microenvironment subtypes based on PD-1/PD-L1 status and CD8+ TIL is an appropriate approach to stratify patients of different clinical outcome and appears to be a predictive biomarker in patients treated with concurrent CRT for inoperable LA- NSCLC. PO-1000 Multicentric restrospective analysis of safety of SBRT to centrally located lesion of the lung L. Frassinelli 1 , P. Borghetti 2 , N. Giaj-Levra 3 , E. D'Angelo 1 , M.L. Bonù 2 , V. Salvestrini 4 , G. Costantino 2 , M. Mariotti 4 , F. Alongi 3 , F. Lohr 1 , V. Scotti 4 , A. Bruni 1 1 University Hospital “Policlinico of Modena”, Department of Oncology and Hematology- Radiotherapy unit, Modena, Italy ; 2 ASST Spedali Civili and University of Brescia, radiation Oncology Department, brescia, Italy ; 3 IRCCS Sacro Cuore Don Calabria Hospital - Negrar, Advanced Radiation Oncology Department, Verona, Italy ; 4 Careggi University Hospital, Department of Oncology- Radiation Therapy Unit, florence, Italy Purpose or Objective Recently SBRT has become the standard of care for inoperable peripheral or central lung lesions from both NSCLC or other histologies. Many studies confirm the safety of SBRT treatment when peripheral lesions are treated, while for central lesion SBRT is still under investigation due to an increased risk of treatment-related serious adverse events. Aim of this multicentric retrospective analysis is to evaluate safety, tolerability and efficacy of SBRT for centrally located pulmonary lesions. Material and Methods Between March 2012 and June 2019, 57 inoperable pts with centrally located pulmonary lesions were submitted to SBRT in four different radiotherapy Italian center. Median age was 73 years (range 50-88 years), the majority were males (43 pts) with Karnowsky Status (KS) equal to 100-90 (48%) or 80 (36%); eight pts have KS equal to 70 and only 1 less than 70. Chest CT and/or 18 FDG PET CT were used to complete the staging. Forty-four pts were submitted to biopsy with histological proven ADK, SCC, neuroendocrine or other histology respectively in 28, 7, 2 and 7 pts. Half of pts were treated for primary or relapse of NSCLC, while 50% for metastasis from another site. Results Median follow up was 16.5 months. All pts were submitted to SBRT using Image guided RT. Forty-five pts were treated with 7-7.5 Gy/fraction (fx) to 60-70 Gy, 6 with 10-12 Gy/fx to 30-36 Gy and 6 with other schedules. Concerning biological equivalent dose (BED) 45 pts had a BED >100 and 12 had BED <100. All pts completed RT treatment course with good tolerance and no interruptions. Acute toxicity were reported in 22% of pts with only 1 case of G3 toxicity