Impact of introducing intensity-modulated radiotherapy (IMRT) on curative intent radiotherapy and survival for lung cancer

Abstract

Introduction: Lung cancer survival remains poor. Intensity-modulated radiotherapy (IMRT) has allowed treatment of more complex tumours as it improves radiotherapy dose conformity around the tumour and greater normal tissue sparing. However, there is limited evidence in the literature assessing the clinical impact of IMRT. In this study, we evaluated whether the introduction of IMRT has influenced the proportion of patients treated with curative-intent radiotherapy over time, and patient survival. Methods: Patients treated with thoracic radiotherapy at our institute between 2005-2020 were retrospectively identified and grouped into three time periods: A) 2005-2008 (pre-IMRT), B) 2009-2012 (some availability IMRT), and C) 2013-2020 (full access IMRT). Data on performance status (PS), stage, age, gross tumour volume (GTV) and survival were collected. The proportion of patients treated with a curative dose between these periods was compared. Multivariable survival models were fitted to evaluate the hazard for patients treated in each time period, adjusting for PS, stage, age and tumour volume. Results: 12,499 patients were included in the analysis (n=2675 (A), n=3127 (B), and n=6697 (C)). The proportion of patients treated with curative-intent radiotherapy increased between the 3 time periods, from 38.1% to 50.2% to 65.6% (p<0.001). This trend was seen across all PS and stages. The GTV increased across time periods. Curative-intent patients treated during period C had a survival improvement compared to time period A (HR=0.725 (0.632-0.831), p<0.001). Conclusion: The introduction of IMRT was associated with more patients receiving curative-intent radiotherapy across all PS and stages of disease. It also facilitated the treatment of larger tumours that historically would have been treated palliatively. Despite treating larger tumours, a survival benefit was seen when full access to IMRT was available (2013-2020). This study highlights the impact IMRT has had on our practice, accepting that improved survival may also be attributed to other contributing factors.