ESTRO 2022 - Abstract Book

S446

Abstract book

ESTRO 2022

Out of all patients, the 5yOS was 78% (95% CI: 76.80 - 79.70), the 2yDMFS was 81.1% (95% CI: 79.80 - 82.30) and the 2yDFS was 80.8% (95% CI: 79.60 - 82.10). Kaplan Meier analysis using Logrank test demonstrated that OS, DMFS and DFS are significantly higher in T-, N-, or stage- downstaged patients (p<0.01). According to the univariate logistic regression analysis, 5yOS, 2yDMFS and 2y DFS were statistically significantly associated (p<0.01) with the downstaging of LARC patients assessed by T-status, N-status and disease stage. Conclusion Downstaging is a very challenging variable for the assessment of the outcomes in LARC. According to the findings obtained in the pooled analysis presented in the current study, downstaging was favorably associated with all survival and disease control outcomes. On the basis of the studies described in the literature, a more focused analysis of this endpoint may lead to the identification of different disease subgroups. These subgroups may benefit from different types and intensifications of treatment in the perspective of personalized medicine.

PD-0497 Prognostic role of GLUT-1 in locally advanced rectal cancer

T.H. Kim 1 , C. Song 2 , J. Kim 2 , Y.J. Kwak 3 , H.S. Lee 3

1 Seoul National University College of Medicine, Department of Radiation Oncology, Seoul, Korea Republic of; 2 Seoul National University Bundang Hospital, Department of Radiation Oncology, Seongnam, Korea Republic of; 3 Seoul National University College of Medicine, Department of Pathology, Seoul, Korea Republic of Purpose or Objective In locally advanced rectal cancer (LARC), the role and extent of adjuvant chemotherapy is still under debate. Meanwhile, some prior studies have shown the possibility of predicting survival outcome with hypoxic markers, especially with glucose transporter-1(GLUT-1) in LARC. This study aimed to investigate the prognostic role of GLUT-1 in LARC using both pre- chemoradiotherapy (CRT) and post-CRT outcomes and to identify groups may benefit from adjuvant chemotherapy. Materials and Methods Pre-CRT and post-CRT (surgical) specimen was collected from 208 patients with clinical T3–4 and/or node-positive rectal adenocarcinoma. All patients received neo-adjuvant CRT followed by total mesorectal excision (TME). Both the pre-CRT and post-CRT specimen were immunohistologically stained for GLUT-1 and compared to distant metastasis free survival (DMFS) and overall survival (OS). Results Median follow up was 74 months. Post-CRT GLUT-1 positivity was significantly associated with inferior DMFS (p=0.027, HR 2.26) and OS (p=0.030, HR 2.30). When patients were classified into 4 groups according to yp Stage II/III and post-CRT GLUT-1 positivity (yp Stage II & GLUT-1(-), yp Stage II & GLUT-1 (+), yp Stage III & GLUT-1 (-), yp Stage III & GLUT-1 (+)), the second and third group showed 5 year DMFS of 63.9% and 65.4% with first group and fourth group showing markedly better and worse outcome of 92.3% and 46.5% (p=0.013). Similar tendency was observed with OS with 5 year OS being 91.7%, 79%, 72.7%, 43.4% respectively for group 1-4 (p=0.008).

Conclusion Post-CRT GLUT-1 has significant association DMFS and OS in LARC, and may serve as a prognostic marker for selecting more fit patients for adjuvant chemotherapy.

PD-0498 Atlas-based auto-segmentation of pelvic CTVs in FDG-PET-CT planning of anal cancer

M.N. Duma 1 , M. Bieder 2 , M. Böhm 3 , M. Freesmeyer 4 , R. Drescher 5 , S. Weimann 1 , A. Wittig 2