ESTRO 2020 Abstract Book

S539 ESTRO 2020

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.

(nivolumab or pembrolizumab) between January 2015 and August 2018 in a French academic hospital. Patients with locally advanced NSCLC who had received local treatments (such as concurrent radiochemotherapy) were excluded. The primary endpoint was progression free survival (PFS) from the onset of immunotherapy. Secondary endpoints were overall survival (OS) from the onset of immunotherapy and safety. Statistical analyses was performed by Chi-squared or the student’s t-test, when indicated. Survival analyses were performed using the Kaplan-Meier method. Univariate and multivariate analyses were performed using the Cox regression model (stepwise for multivariate). Results Overall, 65 patients received previous or concurrent radiotherapy (RT+) and 129 did not (RT-) (Table 1). Patients RT+ had more frequently bone metastases (p<0.001) and brain metastases (p<0.01), but less pleural metastases (p ≤ 0.01). With respect to the RT site, 12% was the thoracic region, 62% was the bone, and 26% was the brain. In the RT+ group, 22% of patients received concurrent RT, and 14% received treatment with curative intent. Median PFS and OS were not significantly different between patients RT+ and RT-: 2.7 vs 3.3 months (p=0.99) and 6.3 vs 8.3 months (p=0.79), respectively. However, in multivariate analysis, previous or concurrent RT was associated with better PFS (HR = 0.63; CI 95%: 0.42-0.94, p = 0.02) and OS (HR = 0.60; IC 95%: 0.39-0.93; p = 0.02). An exploratory univariate analysis evaluating the timing of RT suggested that concurrent RT versus previous RT could be a favorable prognostic factor of PFS (HR : 0.44 ; IC 95% : 0.21-0.91, p = 0.027) (Figure 1). Tolerance was similar in both groups.

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 This monocentric retrospective study included 194 metastatic NSCLC patients treated by an anti-PD1