The potential clinical benefit of respiratory gated radiotherapy (RGRT) in non-small cell lung cancer (NSCLC)

Abstract 

Background

There is a great deal of excitement regarding respiratory gated radiotherapy (RGRT), however there remain potential errors and controversies surrounding its use. We aim to predict an improvement in the clinical outcome of RGRT in comparison with that of continuous (non-gated) irradiation by analysing toxicity parameters.

Materials and methods

The 4DCT scans of 15 patients, with node-positive lung cancer and >5mm of tumour movement, were used for this retrospective analysis. End-inspiration and end-expiration plans were created and the toxicity parameters were compared to continuous (non-gated) 4DCT plans.

Results

Median reduction in V20 with inspiratory gating and expiratory gating, using a 10mm set-up margin, was 2.0% (range 0.7% to 3.9%) and 0.6% (range −1.1% to 4.7%), respectively. The reduction in MLD was 2.1Gy (range 0.6 to 3.9Gy) and 1.6Gy (range −1.0 to 3.9Gy), respectively.

Conclusions

Although there is a widespread excitement regarding this technique, this study demonstrates that there is limited reduction in toxicity parameters with the use of RGRT in comparison with continuous (non-gated) 4DCT irradiation. Due to the additional potential errors involved in RGRT, we feel that currently, it should only be performed if comparative planning of RGRT plans and continuous (non-gated) 4DCT plans has been undertaken and a likely clinical benefit has been confirmed.

Keywords: Respiratory gating, Motion management, 4DCT, Clinical benefit, Toxicity parameters