Assessment of Setup Accuracy Using Anatomical Landmarks for Breast and Chest Wall Irradiation With Surface Guided Radiation Therapy.

PURPOSE: This study aimed to determine setup accuracy using anatomic landmarks for breast irradiation with and without surface guided radiation therapy (SGRT) and assess setup time with SGRT.

METHODS AND MATERIALS: This study included 115 patients with 1945 treatment fractions. Patients were treated with 4 techniques: tangents, tangents using deep-inspiration breath hold, and tangents with regional nodal irradiation with and without deep-inspiration breath hold. A total of 915 portal verification images were analyzed to determine setup errors for the skin, chest wall (CW), and heart. Setup error at each landmark was defined as the mean and maximum distances between the projected planning structure and the delineated structure on the portal image. Setup time for each fraction was determined using 2 recorded time outs: one upon the patient entering the treatment room and another before radiation beam on.

RESULTS: Setup errors for the skin were significantly reduced with SGRT for all 4 treatment techniques (P < .001). On average, the mean and maximum errors for the skin decreased from 3.5 mm to 2.3 mm (P < .001) and from 7.6 mm to 5.6 mm (P < .001), respectively. Setup errors for the CW were not significantly different for tangent treatments, but significantly different for locoregional treatments. For all patients, the average mean and maximum errors for the CW were reduced from 3.1 mm to 3.0 mm (P = .21) and from 6.1 mm to 5.5 mm (P = .001), respectively. No significant change in setup errors for the heart was observed. Setup times with SGRT were slightly longer (P < .01), and the average setup time increased from 5.4 to 6.3 minutes.

CONCLUSIONS: Using anatomic landmarks, we confirm that SGRT improved patient setup accuracy with a slight, but clinically nonsignificant increase in setup time.