ESTRO 36 Abstract Book

S70 ESTRO 36 _______________________________________________________________________________________________

lung dose (MLD) from a mean of 13.8 Gy in noART group to 12.4 Gy in ART (p=0.004). The heart dose was not significantly different between the groups (Table 1). Recurrence at tumour site was 32% and 36% in ART and noART, respectively. The incidence of loco-regional failure was 45% in the adaptive group (ART) and 48% in the control group (noART). Median progression free survival time for the ART-group was 16 months (95%-CI: 13-20), and 19 months (95%-CI: 5-32) for the noART group. The pneumonitis (grade 2 or more) decreased significantly from 50% in the noART group to 33% in the ART group (p=0.001).

Conclusion Incidental dose to the cardiac atria and ventricles did not improve RP risk prediction in our cohort of s tage III NSCLC patients as the DVH parameters for lung o utperformed those for the heart. The multivariable mo del containing the variables cardiac comorbidity and MLD is the optimal model for RP prediction in this cohort. OC-0143 Adaptive radiotherapy reduces pneumonitis without increasing the risk of failure in lung cancer A.A. Khalil 1 , M.M. Knap 1 , M.T. Petersen 1 , M. Kandi 1 , H.H. Schmidt 1 , D.S. Møller 2 , L. Hoffman 2 1 Aarhus University Hospital, Department of Oncology, Aarhus C, Denmark 2 Aarhus University Hospital, Department of Medical Physics, Aarhus C, Denmark Purpose or Objective Radiation pneumonitis (RP) remains the most significant dose-limiting factor in lung radiotherapy (RT). Sparing the volume of the irradiated lung has always been an aim of oncologist but this was hindered by the fear of increasing the local and regional failures. In April 2013 an adaptive strategy with daily online tumour match was introduced in locally advanced lung cancer patients (pts) treated with curative intended RT. The aim of this study was to evaluate the impact of introducing the adaptive strategy on RP as well as on the incidence of failure. Material and Methods Hundred and eight consecutive lung cancer pts receiving RT with an adaptive strategy (ART) using smaller planning target volume (PTV) margins were analysed. A matching control group of 102 consecutive pts (noART) treated prior to April 2013 with bone match and larger margins were analysed. The normal tissue constraints were similar in both groups. RP was scored using CTCAE 4.03. Pts were followed up with CT-scans every third month in both groups and failures were proven histologically . Data analysed included patient and tumour characteristics, chemotherapy given as well as radiation dose. All time analysis was calculated from the RT start date. Kaplan Meier survival analysis was used to estimate the RP and recurrence risk and groups were compared using chi square test. All statistical tests were 2 sided and p<0.05 was considered significant. Results Median follow-up time was 20 months (range 2-56). The gross tumour volume (GTV) was not different between the groups (p=0.8). The PTV was significantly smaller in the ART group as compared to the noART group (p <0.0001). That was accompanied by a significant reduction in mean

Conclusion Implementation of an adaptive strategy and daily tumour match for advanced lung cancer patients significantly decreases the pneumonitis incidence without affecting the loco-regional control rate. OC-0144 Dosimetric analysis of randomized lung proton and photon plans with respect to radiation toxicity T. Deist 1 , P. Yang 2 , C. Oberije 1 , P. Allen 2 , Y. Luo 2 , Y. Van Wijk 1 , D. Gomez 2 , T. X u 2 , S. Tucker 3 , R. Mohan 4 , S. Hahn 2 , P. Lambin 1 , Z. Liao 2 1 MAASTRO Clinic, Department of Radiotherapy, Maastricht, The Netherlands 2 The University of Texas MD Anderson Cancer Center, Department of Radiation Oncology, Houston, USA 3 The University of Texas MD Anderson Cancer Center, Department of Bioinformatics and Computational Biology, Houston, USA 4 The University of Texas MD Anderson Cancer Center, Department of Radiation Physics, Houston, USA