Purpose: To evaluate the impact of fractionation schedule on the size of the gross tumour volume (GTV) effect on tumour control after radiotherapy of NSCLC.
Material and methods: A subgroup analysis on 163 patients treated in a randomized phase III trial of CHARTWEL (continuous hyperfractionated accelerated radiotherapy-weekend less) vs conventional radiotherapy was performed. The influence of GTV and other baseline factors on local failure (LF), disease-free survival (DFS), distant metastases (DM), and overall survival (OS) was estimated using the Cox Proportional Hazards model.
Results: Superior local control was achieved by CHARTWEL compared to conventional radiotherapy (HR 0.54, p=0.015). The hazard of LF increased with increasing GTV for both conventional fractionation and CHARTWEL, however the increase for the latter was less pronounced and not significant.
Conclusion: Highly accelerated CHARTWEL treatment was significantly more effective than conventional radiotherapy for locoregional control of NSCLC. GTV had a significant effect on locoregional control after conventional fractionation, an effect that was not significant with CHARTWEL. This is the first study to demonstrate that the magnitude of the time factor of fractionated radiotherapy increases with tumour volume.
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