SU-E-T-768: Treatment Time Nomogram for Strut-Based Accelerated Partial Breast Applicators
Purpose: The purpose of this work was to generate a tabular nomogram of treatment times for strut-based APBI applicators. The nomogram is intended to provide guidance and a quality assurance check for clinics establishing new treatment techniques or transitioning from balloon-based applicators. Methods: A retrospective analysis was conducted of 486 patients receiving APBI using strut-based applicators at three separate institutions. Strut-based applicators are composed of a central channel surrounded by 6 close-range (“mini”), 6 mid-range, 8, or 10 peripheral channels. Patient data was organized based on applicator size (a surrogate of treatment volume) and number of organs at risk. Three organs at risk categories were determined based on the proximity of the device to the patient’s skin and/or chest wall (0, 1, or 2 OARs). The proximity criterion was defined as being < 5 mm from the cavity wall/peripheral struts. A tabular nomogram of treatment time (based on nominal 10 Ci source strength) was generated from descriptive statistics of each combination of applicator size and organs at risk category. Results: The average treatment time was observed to be directly related to applicator size and, to a lesser extent, inversely related to the number of nearby organs at risk. Distributions of treatment times observed for each combination of applicator size and organs at risk category are depicted in Figure 1. The tabular nomogram featuring average treatment times with standard deviations is presented in Table 1. Conclusion: Strutbased APBI treatment times were observed to depend in a consistent manner on applicator size and number of nearby organs at risk. Information provided in the nomogram presented here represents several hundred treatments performed at multiple institutions. This data can serve as guidance or quality assurance for institutions with limited experience using strut-based APBI applicators.