Photo Credit: Mohammed Haneefa Nizamudeen

The following is a summary of “Validation of in vivo dose using EPID combined with fan-beam CT guidance in post-breast-conserving radiotherapy for early-stage breast cancer,” published in the April 2025 issue of BMC Cancer by Zhu et al. 

This study investigated the clinical value of in vivo dose validation during radiation therapy following breast-conserving surgery in patients with early-stage breast cancer. Specifically, it assessed how image guidance influences dose validation outcomes and examined the role of both inter-fractional and intra-fractional anatomical variations on dose distribution to the target volume and surrounding organs at risk.

A total of 26 patients receiving post-operative radiotherapy for early breast cancer were enrolled in in-treatment in vivo dose validation. Imaging data were used to redefine the target area and critical structures, allowing for a quantitative analysis of dose distribution changes due to inter-fractional (between treatment sessions) and intra-fractional (within a single session) anatomical variations. Retrospective analysis was conducted to evaluate the performance of in vivo dose validation across different imaging modalities.

The results demonstrated that patients treated with image-guided radiotherapy exhibited significantly higher 2D gamma pass (γ-pass) rates for both 3%/3 mm and 5%/3 mm thresholds compared to those receiving non- image-guided radiotherapy (N-IGRT) for both left- and right-sided breast cancers (p < 0.05). Furthermore, the 5%/3 mm γ-pass rate achieved with fan-beam computed tomography (FBCT) guidance was notably higher than that observed with standard IGRT (p < 0.05), underscoring the superior accuracy of FBCT-based dose delivery.

In patients with left-sided breast cancer, significant inter-fractional differences were found in key dosimetric parameters, including PGTV D95, PGTV D2, PTV D95, and PTV D90, as well as heart Dmean and V5, and lung V5 (all p < 0.05). Intra-fractional differences also significantly affected dose distribution, with the exception of heart Dmean. Similar findings were observed in right-sided patients with breast cancer, where both inter- and intra-fractional changes led to significant alterations in dose delivery across all assessed parameters (p < 0.05).

These findings confirm that both inter- and intra-fractional anatomical variations substantially impact dose distribution in breast radiotherapy. The integration of in vivo dose validation using electronic portal imaging devices, particularly when combined with fan-beam CT-based image guidance, enables accurate, real-time assessment of delivered radiation doses. This approach enhances treatment precision, potentially improving therapeutic outcomes while minimizing radiation exposure to surrounding healthy tissues.

Source: bmccancer.biomedcentral.com/articles/10.1186/s12885-025-13431-6