Exploratory Study on Therapy for Breath Hold in Radiotherapy

Due to breathing and other motions, tumours, such as breast and lung cancer, as well as their surrounding organs (e.g. the heart), move, which poses a challenge for radiotherapy treatment. Reducing or even stopping breathing, e.g. by irradiating during inspiration, is a way to decrease tumour and organ motion resulting in a reliable target coverage with smaller margins. These smaller margins can result in a better sparing of normal tissues. Furthermore, in some patients, during inspiration, the heart may move away from the target volume making it possible to better spare the heart. Finally, during inspiration, the lung volume is larger and the lung density is lower, which can lead to a lower dose to the surrounding normal lung tissue. Reduction of radiation dose to normal tissues leads to less radiation-induced toxicity. This makes treating breast and lung cancer patients in breath hold (BH) conditions an attractive strategy. Standard BH durations in RT treatment are around 20 seconds, which is not enough to perform a complete CBCT. The health status of lung cancer patients is generally worse compared to breast cancer patients, making it more difficult to treat this patient group during breath hold. Nasal High Flow Therapy (NHFT) is a non-invasive system that provides controlled oxygen concentrations and low levels of positive pressure via a nasal interface. NHFT improves oxygenation in diverse patient groups, and is increasingly used as an alternative to mechanical ventilatory support. It has been shown to be a safe device in several clinical situations and patient populations, such as COPD patients, but also in apneic conditions under general anesthesia.