A case study of inhale and exhale split-course VMAT treatment to minimize dose to ribs.

Treating at breath-hold has been used to mitigate dose to the organs at risk while maintaining target stability and dose coverage. The breath-hold technique has been used in conjunction with stereotactic body irradiation for the treatment of lung lesions. However, utilizing a breath-hold technique does not help to decrease dose to the ribs when the target is in proximity to the chest wall. The researchers in this case study aimed to demonstrate an alternative route to reduce dose to the chest wall via a novel method of splitting the course of treatment between the inhalation breath-hold and exhalation breath-hold phases of breathing. In this study, the tumor position and movement throughout the respiratory cycle gave ample opportunity to deliver an ablative dose while also decreasing dose to the chest wall and ribs utilizing this "split-course" technique. To minimize the dose and potential for side effects, the course of treatment was divided into 4 fractions of inhalation breath-hold treatment and 4 fractions of exhalation breath-hold treatment. This plan was designed specifically for the patient to help reduce late side effects from radiation therapy. The split-course treatment method significantly decreased the dose to the chest wall and rib. The patient was followed up with evaluations over 9 months after treatment and indicated no pain in the chest.