ESTRO 2021 Abstract Book

S810

ESTRO 2021

Conclusion As comorbidities mainly influence OS, we demonstrated that ACE27 and ASA-Score could significantly stratify patients to different risk groups prior to adjuvant radiotherapy. Both outperformed ECOG-PS on multivariate analysis, confirming the importance of using an objective comorbidity assessment. Further prospective studies are needed to validate our findings. PO-0977 Comparison of therapy outcomes between 2-dimensional radiotherapy and IMRT for early glottic cancer S. Purohit 1 , P. Ahlawat 1 , M. Gairola 1 , S. Tandon 1 , M.I. Sharief 1 , N. Sachdeva 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 Purpose or Objective The use of two-dimensional radiotherapy (2D RT) with parallel opposing fields has been the standard technique for early glottic cancer (EGC). However, there is a controversy about using intensity modulated radiotherapy (IMRT) in this site because of a paucity of sensitive organs at risk to be spared with IMRT. Another concern with IMRT is believed to be probability of marginal miss which may lead to treatment failure. The aim of this study was to compare oncological outcomes and patterns of failure between 2D RT and IMRT for EGC. Materials and Methods It was a retrospective analysis of 284 patients with newly diagnosed EGC (clinical T1 or T2 with without nodal involvement) treated between 2010 to 2017 with radical radiotherapy. T1 tumours were given 66 Gy in 33 fractions, and T2 tumours were given 70 Gy in 35 fractions. The primary end points of this study were loco- regional control (LRC) and overall survival (OS) rates. The other endpoint was patterns of failure. The end points were compared between 2D RT and IMRT. Results Patient characteristics are shown in Table. The two groups were comparable except with regard to alcohol consumption and RT dose. The median follow up in 2D RT and IMRT groups were 54.6 months (range; 4.7 – 124.3), and 48.5 months (range; 3.7 – 115.4) respectively. The median LRC was not achieved with IMRT technique at the time of analysis. The median LRC in 2D RT was 109 months (95% confidence interval [CI], 59.601 – 158.486). There was a trend towards improvement in median LRC in IMRT technique (p = 0.063). The median OS was not achieved with 2D RT. Median OS in IMRT technique was 94 months (95% confidence interval [CI], 82.409 – 106.04). There was no difference in median OS between the two techniques (p = 0.301). The 5 years and 10 years LRC was significantly higher in IMRT than in 2D technique (69.7% vs 57.9%; p = 0.039, and 69.7% vs 55.3%, p = 0.012 respectively). The 5 years and 10 years OS was also significantly higher in IMRT than 2D technique (81.8% vs 67.1%; p = 0.005 and 75.8% vs 64.5%, p = 0.039 respectively). There were 70%, 0% and 30% local, regional alone and loco-regional recurrence in IMRT, and 85.7%, 2.9% and 11.4% local, regional alone and loco-regional recurrence in 2D RT technique (p = 0.034).