ESTRO 37 Abstract book

S57

ESTRO 37

shared their time and expertise as teachers and tutors to make this possible. The ESTRO School has developed a wide spectrum of activities and approaches to support most of the scientific and professional needs of its community. A lot of effort was put in improving the teaching processes. Still, the ESTRO School can do much more and better in the future: gearing up to the challenges ahead and preparing the next generation of radiation oncology professionals to provide excellent care to cancer patients is a life-long responsibility of the ESTRO School. This lecture will discuss opportunities for the School to optimize the teaching approaches and learning outcome, integrate new methodologies and cost- effective technologies for enhanced access to learning and educational resources and scale up radiation oncology education & training worldwide. SP-0109 Lessons Learned from RTOG 0617 J. Bradley 1 1 Washington University School of Medicine, Department of Radiation Oncology, St. Louis, USA Abstract text Topics that will be covered in this session include: Review of the 5-year results from RTOG 0617 Review of multiple secondary analyses: -Quality of life -Value of IMRT -Impact of institutional enrollment volume -Heart DVH data Current concepts escalating radiation dose for NSCLC in North America SP-0110 Combining systemic therapy with hypofractionation in locally dvanced NSCLC: Best of both worlds, or double-trouble? G. Hanna Queen´s University of Belfast, Belfast, the United Kingdom SP-0111 Model-based approach to select the optimal technology for LA-NSCLC J.J. Sonke 1 1 Netherlands Cancer Institute, Radiotherapy department, Amsterdam, The Netherlands Abstract text Locally advanced lung cancer is a challenging disease site to treat with radiation. Tumors are located within and nearby sensitive normal structures, both day-to-day baseline shifts and respiration induce motion of the primary tumor and lymph nodes relative to the bony anatomy and each other, anatomical changes occur frequently and tumor regression is common. Various technologies are being developed to meet those challenges such as kilo-voltage intra-fraction monitoring (KIM), PET guided RT, MR guided RT and proton therapy. Randomized clinical trials, however, are lacking to select the best technology for given patient. In fact, as technologies are not fixed but continuously evolving improvements, it is unlikely that such clinical trials will ever provide a definitive answer. Model-based selection is an alternative approach to guide the use of the optimal technology. In the model based approach, for each patient a treatment plan is made for one or more technologies as well as the standard of care. Subsequently, state of the art normal-tissue complication probability (NTPC) models are used to estimate and compare the likelihood of treatment related toxicities for Symposium: Lung and dose escalation Abstrat not received

each technology of interest. This allows the selection of the optimal technology, in terms of cost and effect. The potential and caveats of this model based approach for LA-NSCLC patient specific technology selection will be discussed. SP-0112 Dose to cardiac substructures predicts survival in non-small cell lung cancer chemo- radiotherapy M. Thor 1 , A. Hotca 2 , A. Jackson 1 , E. Yorke 1 , A. Rimner 2 , J. Deasy 1 1 Memorial Sloan Kettering Cancer Center, Medical Physics, New York City, USA 2 Memorial Sloan Kettering Cancer Center, Radiation Oncology, New York City, USA Purpose or Objective Recent findings suggest that survival after non-small cell lung cancer (NSCLC) chemo-radiotherapy (CRT) drops as dose to the heart increases. We aimed to investigate this further incorporating dose to 13 cardiac substructures, the whole heart, and the tumor-subtracted lung together with disease- and patient characteristics in prediction models for overall survival (OS), and non-cancer related survival (NCS). Material and Methods All structures were re-defined in a total of 179 stage III NSCLC patients receiving CRT in 2004-2014 with prescribed doses of 50-80Gy@1.8-2.0Gy/fraction. Cardiac substructure definition followed that of RTOG 1106, and a semi-automatic atlas-based approach was used for segmentation. For each structure, equivalent dose fractionation correction (α/β=3Gy) was performed, and the mean, max, and minimum dose, as well as the minimum dose to the hottest x% volume (Dx; x=5-95% in 5% steps), and structure volume were extracted. Each of these and a total of 23 disease- (chemo timing, histology, tumor inferiority/laterality/stage/volume), and patient characteristics (age, cardiovascular function, ethnicity, diabetes, hypertension, hyperlipidemia, lung function, performance status, sex, and smoking history) were subject to Cox proportional hazard regression modeling. A candidate variable was suggested if presenting with p≤0.05 (note: Bonferroni-adjusted to p≤0.002 for all dose-volume variables given 23 comparisons/structure), and at most a weak-modest correlation with any other candidate variable (Spearman’s rank correlation coefficient, R s <0.80). Ultimately, a forward-stepwise approach was applied in which a candidate variable was considered final if p≤0.05 of the log-likelihood ratio statistics (p LL ). The number of deaths was 132 and 40 for OS and NCS, respectively. Robustness of p-values for identified final multivariate variables was investigated using Bootstrap resampling (1000 sample populations). Results A total of 102 and 126 dose-volume variables presented with p≤0.05 for OS, and NCS, respectively, but taking into account the R s criterion, the number of candidate dose- volume variables was reduced to five and six (OS, NCS) together with four disease- and patient characteristics for both endpoints. The final models included a total of 2-3 variables: increased left atrium (LA) D min , and worse performance status (OS); increased LA D 95 , electrocardiogram (ECG) abnormalities, and cardiovascular disease (NCS) all being robust on Bootstrap resampling (Figure; Table). Overall, dose-volume variables of cardiac substructures presented with lower p-values compared to those of the whole heart, or the tumor-subtracted total lung.