arXiv:2508.05725v1 Announce Type: new
Abstract: Purpose: To evaluate the cumulative radiobiological impact of daily Megavoltage Cone-Beam Computed Tomography (MV-CBCT) imaging dose based on Normal Tissue Complication Probability (NTCP) and Excess Absolute Risk (EAR) of secondary malignancies among radiotherapy patients treated for breast, pelvic, and head and neck cancers. This study investigated whether MV-CBCT imaging dose warrants protocol personalization according to patient age, anatomical treatment site, and organ-specific radiosensitivity.
Methods: This retrospective study included cohorts of breast (n=30), pelvic (n=17), and head and neck (n=20) cancer patients undergoing radiotherapy with daily MV-CBCT. Imaging plans using two common protocols (5 MU and 10 MU per fraction) were analyzed. NTCP values were estimated using logistic and Lyman-Kutcher-Burman (LKB) models, while EAR was calculated using Schneider’s Organ Equivalent Dose (OED)-based model. Statistical analysis used paired t-tests, and results were further stratified by age (under 40, 40 to 60, over 60 years).
Results: In breast cancer patients, NTCP for lung increased significantly under the 10 MU protocol (p