ESTRO 37 Abstract book

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ESTRO 37

validation cohort (median follow-up: 3 years). Between the two cohorts, there were no significant difference in the 3-year DC (88% [95% CI: 84%-91%] vs. 84% [95% CI: 77%-89%], p=0.16) or OS (72% [95% CI: 67%-77%] vs. 69% [95% CI: 61%-77%], p=0.26). The Multivariable analysis identified pN2-3 and histological grade 2-3 (G2-3) as DM predictors. The high-risk group included patients who had both poor predictors (pN2-3 and G2-3), while low-risk group consisted of patients who had one or no poor predictors. In the discovery cohort, the 3-year DC rate was 78% (95% CI: 70%-84%) and 97% (95% CI: 92%-99%) in high- and low-risk groups respectively (p<0.001), with the concordance index (c-index) of 0.72. In the validation cohort, the risk group classification performed similarly (3-year DC: 69% [95% CI: 54%-79%] vs. 95% [95% CI: 87%- 98%], p<0.001) with the c-index value of 0.73. The 3-year OS for the high- vs. low- risk group was 85% (95% CI: 79- 91%) vs. 95% (95% CI: 91%-98%) in the discovery cohort (p<0.001), and 74% (95% CI: 63-86%) and 93% (95% CI: 87%-99%) in the validation cohort (p<0.001). Conclusion The proposed classification allowed for the definition of a high risk group of DM with poor survival. This validated model (G2-3/pN2-3) could be used to identify OSCC patients who may benefit from: 1) more aggressive screening for DM (before initiating the treatment) in order to avoid unnecessary or inappropriate management, 2) experimental systemic treatment intensification to impact development of DM, and 3) a more aggressive post-treatment surveillance schedule for early detection of DM and consideration of experimental ablative treatments for oligometastatic or early systemic treatment for non-oligometastatic disease. OC-0278 NAR score as surrogate for disease-free survival in the CAO/ARO/AIO-04 phase 3 rectal cancer trial E. Fokas 1 , R. Fietkau 2 , A. Hartmann 3 , W. Hohenberger 4 , R. Grützmann 4 , M. Ghadimi 5 , T. Liersch 5 , P. Ströbel 6 , G. Grabenbauer 7 , C. Wittekind 8 , R. Sauer 2 , M. Kaufmann 9 , T. Hothorn 9 , C. Rödel 1 1 University of Frankfurt, Department of Radiotherapy and Oncology, Frankfurt, Germany 2 University of Erlangen-Nürnberg, Department of Radiation Therapy, Erlangen, Germany 3 University of Erlangen-Nürnberg, Institute of Pathology, Erlangen, Germany 4 University of Erlangen-Nürnberg, Department of General and Visceral Surgery, Erlangen, Germany 5 University Medical Center Göttingen, Department of General- Visceral and Pediatric Surgery, Göttingen, Germany 6 University Medical Center Göttingen, Institute of Pathology, Göttingen, Germany 7 DiaCura & Klinikum Coburg, Department of Radiation Oncology and Radiotherapy, Coburg, Germany 8 University of Leipzig, Institute of Pathology, Leipzig, Germany 9 University of Zurich, Epidemiology- Biostatistics and Prevention Institute, Zurich, Switzerland Purpose or Objective We assessed the recently-developed neoadjuvant rectal (NAR) score that incorporates weighted cT, ypT and ypN categories as a prognostic marker and individual-level surrogate for disease-free survival (DFS) in patients with rectal carcinoma treated in the CAO/ARO/AIO-04 randomized phase 3 trial. Proffered Papers: CL 6: Lower GI

Conclusion We determined a gene signature predicting LRC in a patient cohort with HPV16 DNA negative HNSCC after PORT-C based on whole transcriptome analysis. The signature showed improved performance compared to the 7-gene signature based on a limited hypothesis-driven gene set, indicating that additional genes of high prognostic value were identified. More importantly, the combination of both models allowed for the identification of a subgroup of patients with HPV-negative HNSCC who are on a particularly high risk of developing a recurrence, and may be considered for dose-escalation trials in future. [1] Subramanian et al. Proc Natl Acad Sci U S A. 2005;102:15545-50. [2] Mootha et al. Nat Genet. 2003;34:267-73. [3] Ashburner et al. Nat Genet. 2000;25:25-9. [4] The Gene Ontology Consortium. Nucleic Acids Res. 2015;43:D1049-56. OC-0277 Development and validation of distant metastases risk group classification in oral cavity cancer A. Hosni 1 , S.H. Huang 1 , K. Chiu 1 , W. Xu 2 , J. Su 2 , L. Tong 1 , A. Bayley 1 , S. Bratman 1 , J. Cho 1 , M. Giuliani 1 , J. Kim 1 , B. O’Sullivan 1 , J. Ringash 1 , J. Waldron 1 , J. De Almeida 3 , D. Chepeha 3 , D. Goldstein 3 , A. Hope 1 1 Princess Margaret Cancer Centre, Department of radiation oncology, Toronto, Canada 2 Princess Margaret Cancer Centre, Department of biostatistics, Toronto, Canada 3 Princess Margaret Cancer Centre, Department of Otolaryngology-Head & Neck Surgery/Surgical Oncology, Toronto, Canada Purpose or Objective Distant metastasis (DM) is a major determinant of prognosis in oral cavity squamous cell carcinoma (OSCC). The objective of this study was to define different prognostic groups with regard to DM following postoperative intensity modulated radiotherapy (PO- IMRT). Material and Methods Retrospective review was conducted for OSCC patients treated with curative intent at our institution with PO- IMRT. All patients were staged according to the UICC/AJCC 7 th edition TNM. Two sequential cohorts of OSCC patients compromised the discovery (2005-2012) and validation cohorts (2013-2014). In the discovery cohort, a set of variables was evaluated by multivariable analysis as potential predictors of DM, including: pT- category, pN-category, resection margin status, extranodal extension, histological grade, lymphovascular invasion, perineural invasion, tumor thickness, and use of adjuvant concurrent chemotherapy. We used the competing risk regression method to derive risk-group classification and compared distant control (DC) and overall survival (OS) according to the derived risk-group in the discovery cohort and subsequently in the validation

cohort. Results

Overall 447 patients were included; 300 in the discovery cohort (median follow-up: 4.2 years) and 147 in the