ESTRO 36 Abstract Book

S657 ESTRO 36 _______________________________________________________________________________________________

EP-1217 Non-small cell lung cancer invading the vertebra: what is the optimal strategy for radiation? S. Appel 1 , J. Goldstein 1 , Z. Symon 1 , Y. Lawrence 1 , M. Ben aiun 1 , N. Honig 1 , T. Rabin 1 1 Chaim Sheba Medical Center, Radiation Oncology, Ramat Gan, Israel Purpose or Objective Non-small cell lung cancer that invades the vertebra (T4) may cause significant morbidities if uncontrolled locally with limited options for salvage re-irradiation. The spinal foramina and vertebral body are sites of potential tumor invasion and sparing them may compromise local tumor control probabilities. In our institution, we incorporated the strategy of including the entire vertebra and the spinal canal to the allowed dose in two strategies: shrinking fields and integrated boost. We hypothesized that treating with integrated boost including the spine canal and the vertebral body will result in higher tumor BED than treatment with shrinking fields we retrospectively reviewed 14 cases that were T4 and treated with radiation therapy in our institute and included the spine and vertebra, during the years 2013- 2016. We searched the radiation plans for mean dose to GTV, spine and fraction size. We calculated the biologically effective doses (BED) per the linear quadratic model, for the GTV using α/β=10 and for the spine using α/β=3. In the shrinking fields two calculations were performed for each step, to account for the different doses to the spine. Results • Shrinking field: ( 4 patients) median prescription dose was 59 Gy (55-66 Gy) in 2 Gy per fraction in 29 (26-33) fractions Median GTV dose was 61.3 Gy (57-68.7Gy). The maximal dose to spine with the composite planes, including the exit dose from the boost plan was median of 50.6 Gy (48.4-53.5 Gy). Median BED to PTV was 71Gy (68.1-79.2Gy) GTV was 74.3 Gy (66.6-83 Gy) and to the spine was 82.2 Gy (75.3- 86.4 Gy) • Integrated boost : ( 10 patients) median prescription dose was 61.6 Gy (54-66 Gy) in 2.21 Gy per fraction (1.96-2.28 Gy) in 28 (28-33) fractions. The median GTV dose was 62.6 Gy (55-64.7 Gy). The median maximal dose to the spine was 50 Gy (47.8-52.7Gy), in 1.8 Gy per fraction (1.6-1.9 Gy). Median BED to PTV was 75.2 Gy (64.8-79.2 Gy) GTV was 76.4 Gy (66.6-78.5 Gy), and the median BED to the spine 79.2 Gy (75-85.9 Gy). 1. example of integrated boost treatment color wash. the GTV is bold red and is recieving mean dose of 63 Gy .. the outer red delineates the elective dose and includes the spinal canal and the adjacent vertebra.higher dose is manipulated inside the GTV, to allow higher BED while elective dose is prescrived to the high risk elective area. with off spine boost. Material and Methods

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2. Table 1: Comparison between treatment strategies: Shrinking fields vs. Integrated boost: Doses prescribed to the PTV, actual doses to the GTV and maximal doses to the spine, and the calculated doses to the GTV and the spine according to the linear quadratic model.

Conclusion Integrated boost strategy resulted in modestly higher BED to the PTV and GTV than shrinking fields, and lower BED to the spine. Thus, the integrated boost strategy should be preferred. EP-1218 Prognostic Values of Tumor Markers in Lung Cancer Patients Treated with Definitive 1 Seoul National University Bundang Hospital, Department of Radiation Oncology, Seongnam-si, Korea Republic of Purpose or Objective Prognostic value of serum carcinoembryonic antigen (CEA), squamous cell carcinoma antigen (SCC), cytokeratin 19 fragment antigen 21-1 (Cyfra 21-1) and neuron specific enolase (NSE) has been investigated in patients with early or advanced lung cancer. However, the role of these markers in patients undergoing concurrent chemoradiotherapy (CCRT) for inoperable lung cancer is unclear. Material and Methods In this retrospective study, 179 patients (154 men and 25 women; mean age, 62.2±9.7 years) with inoperable lung cancer underwent definitive CCRT at our institution from 2003 to 2014. Histologic classification was as follows: adenocarcinoma 37 (21%), squamous cell carcinoma 62 (35%), other non-small cell lung cancer (NSCLC) 6 (3%), and small cell carcinoma 74 (41%). Age, gender, histology, tumor diameter, clinical N stage, and pre- and post-CCRT Chemoradiotherapy J.H. Chung 1 , J.S. Kim 1