2937 - Evaluating Patient Comfort and Therapist-Reported Setup Reproducibility In Relation to Cone Beam Computed Tomography (CBCT): Verified Positional Accuracy in Breast Radiotherapy

Purpose/Objective(s): To investigate the role of comfort-driven immobilization in radiotherapy by evaluating both patient-reported comfort and radiation therapists’ observations of positioning and setup reproducibility, with the aim of identifying best practices that optimize treatment accuracy, enhance patient experience, and improve immobilization techniques.

Materials/Methods: This prospective observational study enrolled 50 breast cancer patients receiving radical radiotherapy (=15 fractions) between August 2025 and January 2026. Patient comfort was assessed using a bilingual (Arabic/English) questionnaire at CT simulation and during three treatment phases: phase 1 (first 3 treatment days), phase 2 (middle 3 days), and phase 3 (last 3 days). At the same time, radiation therapists completed structured surveys evaluating setup reproducibility, immobilization device effectiveness, positioning challenges, and treatment interference. Setup accuracy was quantified using 450 CBCT images from Offline Review in the ARIA Oncology Information system, recorded translational and rotational shifts (Deviations) to calculate setup errors. Descriptive statistics were reported as median (IQR) or frequencies (%). Associations between setup errors and questionnaire responses were analyzed using Spearman’s rank correlation, and binary comparisons were performed with the Wilcoxon rank-sum test. A two-sided p = 0.05 was considered statistically significant.

Results:

Median CBCT-derived setup errors were 0.50 mm translationally (IQR 0.41–0.60) and 1.94° rotationally (IQR 1.60–2.64). Correlations between patient-reported comfort and CBCT errors were uniformly weak and non-significant (|?| = 0.04–0.27, p = 0.15). Phase-specific analyses and binary comfort comparisons similarly demonstrated no significant differences in translational or rotational errors (p = 0.36 and p = 0.59, respectively). In contrast, therapist-reported factors showed significant associations. Poorer setup reproducibility correlated with higher rotational error (? = 0.40, p = 0.029). Positioning or device-handling issues were significantly associated with increased translational error (0.60 mm vs 0.44 mm, p = 0.011) and showed a non-significant trend toward higher rotational error (2.64° vs 1.89°, p = 0.098).

Conclusion: Patient comfort did not significantly impact CBCT-verified setup accuracy, suggesting patients maintain stable positioning despite varying comfort levels. Conversely, therapist-reported measures of setup quality—particularly reproducibility and handling issues—were strongly associated with increased errors. These findings indicate that therapist-driven factors exert greater influence on positioning accuracy than patient comfort alone. Enhancing reproducibility protocols, standardizing immobilization practices, and addressing device-handling challenges may offer the most effective strategies for reducing CBCT setup errors in breast radiotherapy.