Abstract Book

S764

ESTRO 37

EP-1400 Outcomes According to SRS Dose Prescription for Brain Metastases from Lung Cancer F. Moraes 1 , J. Winter 2 , A. Dasgupta 1 , H. Razie 1 , C. Coolens 2 , Z. Gelareh 3 , P. Kongkham 3 , M. Bernstein 3 , T. Conrad 1 , N. Laperriere 1 , B. Millar 1 , A. Berlin 1 , D. Shultz 1 1 Princess Margaret Cancer Centre, Radiation Medicine Program, Toronto, Canada 2 Princess Margaret Cancer Centre, Medical Physics, Toronto, Canada 3 Princess Margaret Cancer Centre, Neurosurgery, Toronto, Canada Purpose or Objective At our institution, we commonly treat brain metastases (BM) adjacent to critical structures with a reduced marginal dose prescription (DP) to reduce the likelihood of toxicity. We sought to evaluate the impact of DP on local failure (LF) and radionecrosis (RN) for small- to medium-sized BM (≤ 2 cm) from non-small cell lung cancer. Material and Methods A prospective registry of BM patients treated with gamma knife SRS between 2008 and 2016 was reviewed to determine per lesion rates of LF and RN. Each lesion was followed until LF or RN or at last MRI follow-up. Defined criteria were used to differentiate LF from RN. Whole brain irradiation (WBI) was a censoring event. Freedom from LF (FFLF) and RN (FFRN) were calculated using the Kaplan-Meier product-limit method. Log-rank test was used as a univariate analysis to compare potential predictive factors of LF or RN events. Results From 1,465 potential subjects, 345 small- to medium- sized BM from 151 lung cancer patients were evaluated. Median radiographic follow-up was 10.2 months. Median lesion volume and diameter were 0.17 cm 3 , and 0.81 cm, respectively. Median OS was 17 months (95CI 14.9-19.09) with 1 year OS of 69.13% (95CI 62.9-74.4%). The DP for 71 lesions (21%) was 15 Gy, and ≥ 20 Gy (median 21 Gy; 20- 24Gy) for 274(79%). Most lesions were ≤ 1 cm (65%). Median number of SRS courses was 2 (1-4) and 36 patients received salvage WBI. Sixteen lesions (4%) developed LF and 12 (3%) developed RN. Freedom from local failure at 1 year (FFLF) for 15 Gy, and ≥ 20 Gy, was 80%, and 95%, respectively (p<0.05). FFLF for lesions ≤1cm, and >1 cm, was 95%, and 78%, respectively (p<0.01). Freedom from RN at 1-year (FFRN) for DP 15 Gy, and ≥ 20 Gy, was 98%, and 96%, respectively (p=0.3). FFRN for lesions ≤ 1cm, and > 1 cm, was 98%, and 93%, respectively (p<0.05). FFLF and FFRN for lesions ≤1 cm and >1 cm, according to DP, are shown in Table 1 . Conclusion Lesions > 1 cm showed improved FFLF improvement with higher DP, although this trend did not reach statistical significance. Prospective randomized evaluation is urged to define the optimal DP. EP-1401 FDG and FMISO-PET for guided dose escalation with intensity-modulated radiotherapy in lung cancers. S. Thureau 1 , D. Gensanne 1 , N. Pirault 1 , R. Modzelewski 2 , P. Gouel 2 , P. Bohn 2 , S. Hapdey 2 , P. Vera 2 , B. Dubray 1 1 Centre Henri Becquerel - Quantif EA 4108, Radiotherapy, Rouen, France 2 Centre Henri Becquerel - Quantif EA 4108, Nuclear Medecine, Rouen, France Purpose or Objective Radiotherapy is the reference processing for non- resectable locally advanced non-small cell lung cancer (NSCLC). However, effectiveness of radio-chemotherapy (RTCT) is low and the increase of the dose may be deleterious. Positron emission tomography (PET) is a potential implement for optimization in lung

radiotherapy. This study investigated the feasibility to inscrease the dose to different functionnal targets. Material and Methods Twenty-one non-small lung cancer patients had a FDG- PET and FMISO-PET before the strat of radiotherapy and one FDG-PET during the radiotherapy (at 42Gy). The treatment was planned by intensity-modulated radiotherapy (IMRT) with three different boost at 74Gy : FDG hotspot (70% of SUVmax), FMISO hypoxic target (SUV max 1.4) or per-treatment FDG (40% of SUVmax). For all patients, we have four plans, one standard plan at 66Gy and three experimental plans at 74Gy for each biologic The mean biologic targets were 4.8 cc for FDG hotspot, 38.85 cc for FMISO and 36 cc for FDG per-treatment. In standard plan (66gy), the PTV FDG Hotspot, FMISO and FDG per-treatment receveid a mean D95% at 66.5, 66.9 and 66.8Gy. In the three experimental plans, the dose to specific target volume was higher than given to others biological volumes. For FDG hotspot plan, mean D95% was 72.5Gy to FDG Hotspot PTV versus 67.9 and 67.9Gy for FMISO PTV and per-treatment PTV. For FMISO plan, mean D95% was 72.2Gy to FMISO PTV versus70.4 and 69.5Gy for FDG Hotspot PTV and per-treatment PTV. Lastly, for FDG per-tratment plan, mean D95% was 73.1Gy to FDG per- treatment PTV versus 71.9 and 69.8Gy for FDG hotspoot PTV and FMISO PTV. For the four plans, the dose to organs at risk (lung, spine cord, heart and oesophagus) were respected. Conclusion The different biologic target volumes successfully received the prescribed dose of 74 Gy in compliance with other dose constraints with IMRT technique. The experimental plan provide different doses to each biologic target. EP-1402 Prognostic value of hematological inflammatory markers in patients with non-small cell lung cancer. N. Kishi 1,2 , M. Ogura 1 1 Kishiwada City Hospital, Radiation Oncology, Osaka, Japan 2 Kyoto University Hospital, Radiation Oncology and Image-Applied Therapy, Kyoto, Japan Purpose or Objective Chronic inflammation contributes to carcinogenesis. Hematological inflammatory markers including neutrophil-to-lymphocyte ratio (NLR), platelet-to- lymphocyte ratio (PLR) and lymphocyte-to-monocyte ratio (LMR) predict survival in many malignancies. We aimed to investigate the prognostic value of inflammatory markers in non-small cell lung cancer patients treated with chemoradiotherapy. Material and Methods Seventy-nine patients with lung cancer who underwent concurrent chemoradiotherapy were studied at our institution between April 2009 and March 2016. The median age was 68 years (range, 45-79 years). According to the UICC 7th edition, there were 9 patients in Stage II, 46 in Stage IIIA and 24 in Stage IIIB. The median prescribed dose was 60 Gy (4-66 Gy). Pretreatment NLR, PLR and LMR were investigated in all patients. The Kaplan-Meier method and log-rank test were used to calculate overall survival (OS), progression-free survival (PFS) and statistical significance. Results The median follow-up period was 27.5 months (1-86 months). The median OS was 31.5 months. Five-year OS for Stage II, IIIA and IIIB were 57.1%, 33.4% and 26.8%, respectively. The median PFS was 12.0 months. The median values of NLR, PLR and LMR were 2.97 (1.16- 18.9), 153.1 (55.4-541.1) and 3.31 (1.05-13.9), respectively. On univariate analysis, high LMR (> 3.31) target. Results