ESTRO 2021 Abstract Book

S812

ESTRO 2021

Conclusion LDRT combined with neoadjuvant chemotherapy could improve the ORR for primary tumor and lymph nodes in high-risk LA-NPC patients, especially for lymph nodes. This new treatment model could be a promising strategy to improve local control, and needed to be confirmed in the future practice. PO-0979 Tumour volume as prognostic factor for recurrent head and neck cancers treated with re- irradiation P. Ahlawat 1 , M. Gairola 2 , S. Tandon 1 , S. Purohit 1 , N. Sachdeva 1 , M.I. Sharief 1 , T. Singh 1 , K. Dobriyal 1 , A. Krishnan 1 1 Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, Radiation Oncology, New Delhi, India; 2 Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, Radiation Oncology, Delhi, India Purpose or Objective The largest diameter of head and neck cancers (HNC) measured for T-stage may not necessarily reflect the true tumour dimensions. Many studies in past have established beyond doubt that tumour volume (TV) measured in 3-dimension is a poor prognostic factor in newly diagnosed HNC treated with radiation radiotherapy (RT). However, no study till date has investigated the impact of TV on outcomes in re-irradiation (Re-RT) setting. The aim of this study was to explore the impact of TV on previously irradiated locally recurrent unresectable HNC treated with Re-RT. Materials and Methods Previously irradiated HNC patients who developed recurrent unresectable HNC were included in this study. Patients who received neoadjuvant chemotherapy were excluded. All underwent radical Re-RT with intensity modulated radiotherapy technique with or without concurrent chemotherapy. Their TV were measured on diagnostic magnetic resonance imaging or positron emission tomography–computed tomography. The end point was loco-regional control (LRC). Multivariate analysis was performed using the Cox proportional hazard model to identify prognostic factors for LRC. Results Sixty-one patients were found to be eligible for the study. Univariate Cox regression model showed increasing age, increasing T-stage, higher Re-RT dose and increasing TV being prognostic factors for LRC. However, multivariate Cox proportional hazards regression analysis revealed increasing Re-RT dose and higher TV as prognostic factors for LRC. Univariate and multivariate analysis for LRC are shown in Table.

Conclusion TV of previously irradiated locally recurrent unresectable HNC treated with radical Re-RT is a strong prognostic factor for LRC.