ESTRO 2021 Abstract Book

S189

ESTRO 2021

Conclusion Hypoxia gene expression is a prominent prognostic factor for DFS for LACC with SCC histology. Such knowledge should be considered when selecting high risk patients for adjuvant systemic treatment following CRT and BT.

¹doi: 10.3109/0284186X.2016.1167959 ²doi: 10.1016/j.ijrobp.2019.11.031

OC-0280 Tumour hypoxia and immunity as predictors of chemoradiotherapy outcome in cervical cancer C. Fjeldbo 1 , V.E. Skingen 1 , E. Aarnes 1 , G.B. Kristensen 2,3 , H. Lyng 1,4 1 Oslo University Hospital, Norwegian Radium Hospital, Department of Radiation Biology, Oslo, Norway; 2 Oslo University Hospital, Norwegian Radium Hospital, Department of Gynaecologic Oncology, Oslo, Norway; 3 Oslo University Hospital, Norwegian Radium Hospital, Institute for Cancer Genetics and Informatics, Oslo, Norway; 4 University of Oslo, Department of Physics, Oslo, Norway Purpose or Objective Tumour hypoxia is an adverse factor in radiotherapy. Oxygen fixates radiation induced DNA breaks, resulting in radioresistance of hypoxic tumours. Moreover, inhibition of anti-tumour immunity by the hypoxic microenvironment has been proposed, and this may impair the response of hypoxic tumours to radiotherapy as well as immunotherapy. An understanding of how hypoxia and immunity are related is thus important for developing improved personalized treatment strategies. We have previously presented a prognostic 6-gene hypoxia classifier in locally advanced cervical cancer. The aims of this work were to evaluate its association to tumour immunity, and determine the benefit of including immunity together with the hypoxia classifier in prediction of chemoradiotherapy outcome. Materials and Methods Illumina bead array gene expression data were obtained from tumour biopsies of 280 patients with locally advanced cervical cancer planned for chemoradiotherapy. The 6-gene hypoxia classifier was used to classify the tumours as more or less hypoxic. The ESTIMATE immune score, reflecting the infiltration level of immune cells in tumour tissues based on gene expression data, was used to assess immunity. Tumour infiltration of CD8+ lymphocytes was detected by immunohistochemistry in 260 patients, and quantified by digital pathology. Results Patients with a more hypoxic tumour had poor progression free survival (PFS) compared to those with a less hypoxic tumour (58% vs 79%, HR = 2.4). However, some patients with a less hypoxic tumour experienced recurrence and some with a more hypoxic tumour were cured, showing that additional mechanisms than those captured by the hypoxia classifier were involved in recurrence. Immune score and density of CD8+ tumour-