Lung cancer is one of the most frequent cancer types, resulting in highest number of cancer related deaths worldwide. Patients with locally advanced lung cancer face poor survival and high risk of severe treatment related side effects, such as lung and cardiac damage, caused by intensive chemo- and radiotherapy.
In patients with breast cancer and mediastinal lymphoma, a cost-efficient technique with deep inspiration breath hold (DIBH) has been applied for over a decade to reduce radiation dose to the lungs and the heart, without any detriment to other organs or to the target. In DIBH radiotherapy, patients hold their breath during imaging and treatment delivery. DIBH results in profound anatomic changes: tumour motion is mitigated, the heart is drawn downwards and the lungs are inflated.
Use of the DIBH in lung cancer radiotherapy has been limited. The aim of this thesis was to investigate all aspects of DIBH as a strategy for radiotherapy of patients with locally advanced lung cancer, to assure a safe and meaningful implementation of the DIBH in the clinic and evaluate the potential of reducing the dose to the healthy tissue.
We showed that the majority of lung cancer patients could comply with the DIBH technique and hold several consecutive DIBHs of 20 s duration with reproducible tumour position. The remaining uncertainties in the tumour position in consecutive DIBHs have been included in the treatment margins, to ensure sufficient target coverage during DIBH radiotherapy.
Mitigated anatomy motion in the thorax during DIBH resulted in improved image quality of daily image guidance, which translated into reduced observer uncertainty and hence improved the treatment precision.
Performance of advanced dose calculation algorithms in low density tissue has been investigated and use of best available algorithm is warranted, especially in DIBH.
The changed anatomy in DIBH facilitated reduction of dose to the lungs and, in most patients, also to the heart. For a few patients, DIBH enabled pursuing the treatment with curative intent, which would not have been possible with radiotherapy in free breathing.
Continuous clinical follow up of the patients, treated in DIBH, will show how the calculated reduced risk will translate into reduced rate of treatment related side effects.