2984 - Institutional Experience with Physicist Planning Time for CBCT-Guided Online Adaptive Radiotherapy

Purpose/Objective(s): Online adaptive radiotherapy (ART) is an emerging technology that offers the potential to improve target coverage and reduce normal tissue dose. However, these benefits come with increased treatment complexity and resource utilization, particularly staffing requirements and longer on-table times for patients. Longer appointment times limit how many patients can be offered ART. There is little published guidance on expected treatment times or strategies to improve efficiency while maintaining safety and quality. This work analyzes median adaptive treatment times and evaluates the impact of a structured credentialing program on CBCT-guided online ART planning efficiency.

Materials/Methods: A credentialing program was developed to onboard new medical physicists leading the contouring and optimization component of online ART for a CBCT-guided platform. Physicists were trained to reduce the time physicians spent at the machine. The program prepares the physicist (“pilot”) to independently perform adaptive cases through demonstration of anatomic knowledge, contouring accuracy, proficiency with the adaptive planning workspace and algorithms, and completion of practice cases in a treatment planning workspace emulator. The performance of one newly credentialed physicist on clinical cases was compared to five experienced physicists who have served or are currently serving as ART pilots.

Results: The primary disease sites treated with online ART at our institution include cervical cancer (cervix, uterus, and lymph nodes), prostate/fossa with lymph nodes, and prostate/fossa alone. For the newly credentialed physicist, planning efficiency improved with experience over their first 50 ART cases. Excess contouring and optimization time relative to experienced peer medians decreased significantly with increasing case number (Spearman ? = -0.30, p - 0.040). Mean excess time decreased from 6.6 minutes during the first 20 cases to 2.7 minutes during the final 20 cases.

Conclusion: At our institution, online adaptive radiotherapy adds approximately 10-25 minutes of on-table time per fraction relative to non-adaptive treatments, with most cases requiring less than 20 additional minutes. Site-specific time variation is likely due to multiple factors, including complexity/size of target volumes and visibility of anatomy. Early experience suggests that a structured credentialing program may lead to improved physicist efficiency over time, with convergence toward departmental median performance. Future work will expand this program to additional physicists and refine training strategies with the goal of increasing competence and reducing the number of cases required to meet median performance.