Abstract
OBJECTIVE: This study aimed to investigate the use of in vivo dose validation during post-breast-conserving radiation for early breast cancer, the impact of image guidance on validation outcomes, and the role of inter- and intra-fractional variations on dose distribution. METHODS: Twenty-six patients undergoing post-breast-conserving radiotherapy for early-stage breast cancer were selected for in-treatment in vivo dose validation. The target area and organs at risk were re-defined using the image-guided images to quantitatively evaluate the impact of inter- and intra-fractional differences on the dose distribution. The retrospective analysis examined the in vivo dose validation outcomes. RESULTS: The 3%3 mm/5%3 mm 2Dγ-pass (gamma pass) rates in the image-guided radiotherapy(IGRT) group were significantly higher than those in the non-IGRT(N-IGRT) group for both left and right breast cancer (p < 0.05). Furthermore, the 5%3 mm 2Dγ-pass rate of the fan-beam CT(FBCT) group was higher than that of the IGRT group and was statistically significant (p < 0.05). The target area parameters primary gross tumor volume (PGTV) D95, PGTV D2, planning target volume (PTV) D95, PTV D90, heart Dmean and V5, lung V5, and inter-fractional differences were statistically significant (p < 0.05) in patients with left breast cancer. The effects of intra-fractional differences on dose distribution were statistically significant except for cardiac Dmean (p < 0.05). Similarly, the dose distribution of measures including PGTV D95, PGTV D2, PTV D95, PTV D90, Heart Dmean, and Lung V5 was strongly impacted by inter-fractional variances in patients with right breast cancer. The influence of intra-fractional differences on dose distribution was statistically significant for all parameters (p < 0.05), and they were statistically significant (p < 0.05). CONCLUSION: When paired with fan-beam CT image guidance, electronic portal imaging device (EPID) in vivo dose validation provides a precise real-time dose delivery evaluation for patients undergoing radiation therapy for breast cancer.