Abstract P4-12-29: Utility of surface guide radiation therapy (SGRT) in radiation therapy for breast cancer
Authors: Desai Snehal 
Published: March 2020

Abstract
Purpose: Radiation therapy has been shown to be a highly effective treatment for breast cancer. Historically, patient setup for daily treatment has required a set of permanent tattoos. However, due to a variety of reasons, it may be hard to align patients to these marks and the marks can also cause distress in many patients. National Comprehensive Cancer Network’s (NCCN) radiation therapy guidelines recommend weekly radiation ports films; however, many centers perform daily image guidance using x-rays for breast treatments prior to radiation delivery, increasing both radiation dose and treatment time. Surface Guided Radiation Therapy (SGRT) is a technique which is being adopted by radiation therapy centers to aid in patient’s setup and treatment delivery accuracy. SGRT is safe and non-invasive, using visible light to compare the patient’s skin surface in the treatment room to the planned treatment position with sub-millimeter accuracy. SGRT can also automatically signal for the treatment delivery system to pause radiation if the patient moves out of the desired position. The aim of this study was to evaluate the AlignRT (Vision RT, Ltd, London, United Kingdom) SGRT system for patient setup accuracy in comparison to a 3-point tattoo setup and daily KV pair imaging. Methods: A total of 20 breast cancer patients (600 radiation fractions) were setup using a 3-point tattoo technique and then positioned using AlignRT. Inter-fraction positions were analyzed between all three techniques, namely tattoo, AlignRT and kV imaging. In addition, the AlignRT system was used to evaluate that patient’s position during breath hold. This deep inspiration breath hold (DIBH) technique is designed to provide cardiac sparing during left breast radiotherapy. Results: Using 3-point tattoo setup, an average magnitude of 5.7±3 mm error from isocenter was measured, compared to 2.4±1 mm using surface guidance. Statistically significant 3d shift vectors were found between patient setup using 3-point tattoo and SGRT techniques, however between SGRT and daily KV imaging 3d shift vectors were not statistically significant. AlignRT based DIBH showed the distance between the heart and chest-wall at the mid tangential beam level, based on weekly port films, to be within 2±1 mm of the planned level. Conclusion: SGRT has been shown to improve the accuracy of patient setup compared to 3-point tattoos and is comparable to daily KV imaging for isocentric setup. SGRT can be used in clinics to reduce the frequency of KV imaging and therefore additional radiation exposure. SGRT can also remove setup tattoo requirements which are placed during simulation which provide a permanent reminder to patients of their cancer and treatment. SGRT has also been demonstrated to ensure adequate and reproducible breath hold for DIBH left sided breast treatments.
Citation Format: Snehal Desai. Utility of surface guide radiation therapy (SGRT) in radiation therapy for breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-29.