ESTRO 2020 Abstract Book

S547 ESTRO 2020

metastases were; brain (32%), lung (25%), bone (15%), adrenal gland (13) and lymph nodes (9%). Approximately half of the patients had an adenocarcinoma (53%), followed by squamous cell carcinoma (28%). The treatment sequence was 45% concurrent chemo-radiation therapy, 33% sequential therapy and 15% received no systemic therapy. The median OS was 17 months (95% CI; 14-20 months) and the median PFS was 9 months (95% CI; 8-11 months). The 1-, 2-, 3-, and 5-year OS and PFS were respectively; 55%, 31%, 21%, 6% and 34%, 16%, 12%, 4%. On multivariate analysis weight loss (HR 1.40, p=0.012), M- stage (HR 1.79, p=0.008) and lateralization of the primary tumor (HR 1.80, p=0.003) remained significantly associated with OS. The c-statistic for this model (corrected for optimism) was 0.63. M-stage (HR 2.22, p<0.001) and lateralization of the primary tumor (HR 1.48, p=0.031) remained significantly associated with PFS. The C-statistic for this model (corrected for optimism) was 0.65. In table 1 we calculated the negative predictive value for low-risk patients at 1 and 2 years OS/PFS. Percentage * Negative predictive value (NPV)** 95% Confidence interval (CI)*** 1 year OS 62.2 75.8 63.7-85.8 2 years OS 36.0 54.1 40.9-66.9 1 year PFS 38.2 47.9 35.9-60.1 2 years PFS 18.9 25.0 15.3-37.0 *OS and PFS in percentage for all included patients that had no missing data. **NPV for low-risk patients based on significant prognostic factors from the multivariate analysis ***CI for the NPV Conclusion M-stage and lateralization of the primary tumor are prognostic factors for OS and PFS. Weight loss is also a prognostic factor for OS. Both models need further improvement to create a tool for better patient selection. PO-1026 Role of neoadjuvant radiochemotherapy in non-Pancoast T4 N0/1 M0 NSCLC PO-1027 Disease natural history of lung oligometastatic colo-rectal cancer patients treated with SBRT L. Nicosia 1 , F. Cuccia 1 , M. Rigo 1 , V. Figlia 1 , N. Giaj-Levra 1 , R. Mazzola 1 , F. Ricchetti 1 , D. Tomasini 2 , F. Alongi 1 1 Ospedale Sacro Cuore "Don Calabria", Radiation Oncology, Negrar, Italy ; 2 ASST Spedali Civili di Brescia - Brescia University, Radiation Oncology Department, Brescia, Italy Purpose or Objective metastatic colo-rectal cancer has a poor prognosis. Stereotactic body radiotherapy (SBRT) demonstrated to increase survival in the oligometastatic disease (OMD). Nevertheless, local control of colo-rectal metastases seems to be poor, as compared to other histologies. Our study aims to explore the natural history of oligometastatic colon-rectal cancer and to determine how SBRT can delay the progression to the polymetastatic disease (PMD). Biological predictive factors of response to SBRT were also evaluated. Material and Methods 131 lung oligometastases in 47 patients were treated with SBRT at our Institution. The median number of treated lesions was 2 (range 1-5). The initial disease stage was: I- Abstract withdrawn

II in 12 patients, III in 14 patients and IV in 11. Median BED 10Gy was 100 Gy (range 75-180). Time to PMD (ttPMD) was defined as the time from the SBRT to the occurrence of >5 new metastases. EGFR, KRAS, NRAS, BRAF, and microsatellite instability were evaluated as predictive factors of response. Results The median follow-up was 31 months (range 3-66 months) and the median time to the oligometastatic disease occurrence was 37 months (range 24-72 months). Median ttPMC was 25.8 months (range 10-46 months). Median Progression-free survival (PFS) was 7 months (range 4-9 months). At the last follow-up, 9 patients (19.2%) are free from disease and 38 (80.8%) progressed: 21 out of them again as oligometastatic and 17 as polymetastatic. Patients with a second oligoprogression received a second SBRT course. Median OS was 39.5 months (range 26-64 months) and the 2-year OS was 71.1%. Three-year local progression-free survival (LPFS) was 80%. At the univariate analysis BRAF wild-type correlated with better LPFS (p=0.003) and PMC correlated with worse OS (p=0.00). Conclusion Our results support the use of SBRT in lung OMD, as it can delay the transition to the PMD, leading to higher OS rates. Notably, in a significant proportion of patients, we observed an oligometastatic progression amenable of a second SBRT course. Molecular factors predictive of response were identified; future larger studies may further investigate a potential prognostic role of tumor genotyping for radiotherapy personalization. PO-1028 Consolidation therapy with Durvalumab after radical CRT in stage IIII NSCLC: a preliminar analysis P. Borghetti 1 , G. Volpi 1 , J. Imbrescia 1 , M.L. Bonù 1 , A. Guerini 1 , O. Turla 1 , M. Maddalo 1 , P. Vitali 1 , L. Triggiani 1 , A. Donofrio 1 , M. Buglione 1 , S.M. Magrini 1 1 Spedali Civili di Brescia, Istituto del Radio, Brescia, Italy Purpose or Objective The PACIFIC trial investigated Durvalumab consolidation after chemoradiation treatment (CRT) in patients with unresectable, stage III NSCLC who have not progressed after CCRT. The relevant overall survival benefit in Durvalumab arm has sensibly influenced the managment of the patients treated with a curative intent. The aim of this study consists in a preliminar evaluation in terms of toxicities and critical issues related to selection and management of eligible patients to Durvalumab as consolidation immunotherapy Material and Methods Still on going, from September 2018 all the patients with unresectable, stage III NSCLC treated at Radiation Oncology Department of Spedali Civili and University of Brescia with CRT were evaluated. Patients eligible to Durvalumab as maintenance treatment were selected for this descriptive analysis. In this group of patients, toxicity profile and the main issues related to inclusion criteria for Durvalumab were explored. Results Nineteen patients were treated with CRT, all of them received radiotherapy (60 Gy/2fr), 15 with concomitant platinum based chemotherapy (median cycles number 5) and 4 with sequential schedule (median cycles number 3,5) The assessment of response with CT scan was done at a median time of 41,5 days (29-68). All the patients had a partial response. Clinical and therapeutic data are reported in table 1. Seven patients were not eligible to Durvalumab maintenance (3 for unknown PDL1 value and 4 for PDL1<1%). Two patients are waiting for CT scan and one refused Durvalumab. None patients met the other exclusion criteria such as disease progression, radiation pneumonitis and active or previous autoimmune disease. After a median number of 6 (1-24) administrations, one patient had an oligoprogression (after 16 cycles) and one