Evaluation of the Motion Range using Surface Mapping System during the Deep Inspiration Breath Hold for Left-Sided Breast Cancer Patients

Abstract

Radiation Therapy (RT) for left-sided breast cancer can cause late cardiac complications. Deep Inspiration Breath Hold (DIBH) during RT has been accepted as an effective approach to reduce the irradiated heart volume as well as reduce the motion of the tumor bed. However, the range of motion /reproducibility of each breath hold (BH) has not been quantitatively studied. Here, we report the results of our evaluation of the motion recorded using a surface guided radiotherapy (SGRT) solution during DIBH manipulated by Active Breath Control (ABC) device. Patients with stages I/II left-sided breast cancer received 3D conformal treatments on a radiation therapy system. For each of the tangential beams, radiation was delivered during 1 or 2 breath-holds with the duration controlled by ABC device. In addition, each patient’s motion was monitored by a CatalystHD (C-RAD, Uppsala, Sweden) SGRT solution which consists of 3 high resolution camera/detector pairs. The motion within each breath hold duration at deep inspiration level, which was represented by a virtual tracking point on patient’s left chest wall, was recorded using the CatalystHD. The range of motion during Inter-BH and Intra-BH were statistically analyzed. A total of 47 ABC treatment sessions including 136 BHs were evaluated for five patients. All patients received tangential radiation to the breast/chest wall (typical doses 180 cGy x 28 or 266 cGy x 16); and all patients received a tumor bed boost. The range of motion varied from patient to patient. The patient with the least chest-wall motion during BH showed a 2.5(±0.7)-mm Inter-BH motion and 1.3(±0.4)-mm Intra-BH motion. On the other hand, the most Inter-BH motion and Intra-BH motion observed for one patient was 13.0(±5.4) mm and 9.4(±3.2) mm. Among 136 BHs, the average of Inter-BH motion and Intra-BH motion were 7.1(±4.9) mm and 4.7(±3.9) mm, respectively. The average duration of DIBH was 13.5(±7.8) s. The range of the motion during DIBH manipulated by ABC is not negligible. It varies between patients and even varies among the different BHs of the same patient on the same day. It should be monitored carefully to ensure appropriate target dose coverage and to prevent the development of late cardiac complications. Additionally, the surface guided system, with proper coaching and the assist of a video-based coaching system (e.g. goggles), can be used as an alternative to monitor the respiratory motion at DIBH in left breast cancer patients who have difficulty breathing through a mouthpiece or who cannot tolerate the ABC device.