Feasibility and Impact of an RTT-Driven Workflow for CBCT-Guided Partial Breast Adaptive Radiotherapy.

Objective: Cone-beam computed tomography (CBCT)-based online adaptive radiotherapy (ART) allows significantly smaller planning target volume (PTV) margins for patients treated with adaptive stereotactic partial breast irradiation (A-SPBI). However, this approach places increased demands on the treatment team, especially physicians. We hypothesize that with appropriate training, physicians' involvement at the treatment console can be reduced by delegating contouring and planning tasks to radiation therapy technologists (RTTs) with a physicist co-pilot without reducing treatment quality.

Methods: In this prospective study designed to evaluate an RTT-driven workflow, 23 patients undergoing A-SPBI were included, with two treatment plans generated per adaptive fraction. The first plan used contours edited by RTTs under physicist supervision (without physician oversight), and the second plan used contours edited by physicians. RTT-modified plans were compared with physician-edited contours for target coverage (V100% and V95%) and organ-at-risk (OAR) constraints. Dice coefficient and Hausdorff distance were calculated for target volumes. Following confirmation of RTT contour quality, we initiated the 'remote physician' workflow to further reduce physician demand in the on-couch process. Physician review time was recorded to estimate the reduction in time required for ART. The number of treated fractions before and after implementation was also tracked.

Results: Analysis of 103 adaptive fractions showed mean Dice coefficient 0.96 for the tumor bed. Mean Hausdorff distance was 0.6 mm. Differences in planning target volume coverage were -1.0 ± 2.2% and -0.6 ± 1.3% for V100% and V95%, respectively. Similar metrics for the tumor bed and clinical target volume had differences <0.4%. Physician time for ART was reduced by 12.3 ± 1.0 minutes per fraction, leading to a 224% increase in ART breast volume at our institution.

Conclusions: Training experienced radiation therapists to perform contouring and planning tasks reduces physician workload without compromising treatment quality during online A-SPBI. Remote contour review ensures ongoing quality and consistency.