ESTRO 2020 Abstract Book

S533 ESTRO 2020

Results We received a total of 255 responses (response rate: 18%). Of which 203 (80%) were completed and returned and thus eligible for further evaluation. The respondents work in 87 different cities and 44% in a private medical practice, 29% in university and 22% in a general hospital. Responses of the same department were analysed for congruence. Durvalumab was implemented in clinical routine by 143 (70%) respondents. Reasons for failed implementation in clinical practice were patient ineligibility, decision of medical oncologists or absence of updated German evidence review (S3-guidelines) regarding this treatment approach. Durvalumab was generally administered according to the respondents by private oncological practices in 32%, general or university hospital in 57% and in the radiation oncology department, which delivered the CRT in 11% of cases. Importantly, according to 36% of all respondents initial PD-L1 status was present in ≤30% of all patients. 82% of respondents have treated 1-15 patients with durvalumab and 14% of respondents >15 patients. Furthermore, no respondent had applied durvalumab in less than 14 days after the completion of CRT. 65 (46%) and 49 (34%) respondents started durvalumab 14-28 days and later than 28 days after CRT, respectively. The majority of respondents (>80%) re-staged the patients with CT (thorax/upper abdomen) prior to durvalumab. Severe side effects requiring hospital admission in more than 10% of all patients were reported by only 12% of all respondents. Conclusion Durvalumab was implemented in the multimodal treatment of inoperable stage III NSCLC and administered by the absolute majority of respondents. Low testing rates of PD-L1 at initial diagnosis were observed and should be considered a major barrier to universal adoption and integration in the clinical work-flow. No respondent applies durvalumab in less than 14 days after CRT and reasons of treatment delay need to be evaluated in further studies. Durvalumab appears to be well tolerated. However, treatment-related side effects need to be considered during and after multimodal therapy. PO-0999 Deciphering the tumor microenviroment based on PD-L1 expression and CD8+ TILs density in LA-NSCLC L. Käsmann 1 , K. Gennen 1 , J. Taugner 1 , C. Eze 1 , M. Karin 1 , O. Roengvoraphoj 1 , J. Neumann 2 , A. Tufman 3 , M. Orth 1 , S. Reu 4 , C. Belka 1 , F. Manapov 1 1 LMU University Hospital Grosshadern, Department of Radiation Oncology, Munich, Germany ; 2 LMU Ludwig- Maximilians-University, Department of Pathology, Munich, Germany ; 3 LMU University Hospital Innenstadt, Department of Pneumology, Munich, Germany ; 4 University Wuerzburg, Department of Pathology, Wuerzburg, Germany Purpose or Objective The prognostic role of the tumor immune microenvironment in multimodal treatment for locally advanced non-small cell lung cancer (LA-NSCLC) is unclear. Increasing evidence suggests treatment benefit depending on tumor cell PD-L1 expression. The purpose of this retrospective single-center study was to investigate the prognostic value of PD-L1 expression on tumor cells in combination with CD8+ tumor stroma-infiltrating lymphocytes (TILs) density in inoperable LA-NSCLC treated with concurrent chemoradiotherapy (CRT). Material and Methods We collected retrospectively clinical characteristics and initial tumor biopsy samples of 31 inoperable LA-NSCLC patients treated with concurrent CRT. PD-L1 expression on tumor cells (0% versus ≥1%), CD8+ TILs density (0-40% vs. 41-100%) and tumor immune microenvironment (TIME) classification (stratification into four subgroups: PD- L1neg/CD8low, PD-L1neg/CD8high, PD-L1pos/CD8low

versus PD-L1pos/CD8high) were evaluated for potential prognostic value in terms of local control, progression-free (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