What question did this study set out to answer?

This research aims to compare the dosimetric impacts of TomoDirect and intensity-modulated radiotherapy in patients undergoing hypofractionated treatment for left-sided breast cancer.

April 1, 2026Open Access

Retrospective Dosimetric Comparison of TomoDirect and Intensity-Modulated Radiotherapy in Hypofractionated Radiotherapy With Simultaneous Integrated Boost for Left-Sided Breast Cancer: Implications for Organ Sparing and Treatment Optimization

JWJ. WangSecond Affiliated Hospital of Inner Mongolia Medical University ZLZi-Hong LiSecond Affiliated Hospital of Inner Mongolia Medical University JGJia-Xing GuoSecond Affiliated Hospital of Inner Mongolia Medical University

Key Points

This research aims to compare the dosimetric impacts of TomoDirect and intensity-modulated radiotherapy in patients undergoing hypofractionated treatment for left-sided breast cancer.
Retrospective dosimetric comparison with 30 patients enrolled.
Acquisition of CT images with 5 mm slice thickness.
Treatment plans developed using Pinnacle and TomoHD planning systems.
Three treatment plans were generated for each patient: TD with field widths of 2.5 cm and 5 cm, and IMRT.
TD (FW = 2.5 cm) showed the lowest homogeneity index values for PGTV and PTV.
IMRT had the highest conformity index values for PGTV and PTV.
TD (FW = 2.5 cm) provided the lowest mean dose to the left lung, heart, and left anterior descending coronary artery.
Average treatment time was shorter for TD (FW = 5 cm) compared to TD (FW = 2.5 cm).

Abstract

Background: TomoDirect (TD) and intensity-modulated radiotherapy (IMRT) are advanced techniques used in hypofractionated radiotherapy with simultaneous integrated boost (HFRT-SIB) for patients undergoing breast-conserving surgery. This study evaluates the dosimetric impacts of TD and IMRT on the target volume areas and organs at risk (OARs). Methods: This study is a retrospective dosimetric comparison. Thirty patients were enrolled. Computed tomography (CT) images were acquired with a slice thickness of 5 mm. The CT data were subsequently exported to the Pinnacle treatment planning system. IMRT plans were developed using Pinnacle. The TomoHDTM planning station was used for TD planning. For each patient, three treatment plans were generated: TD (field width FW = 2.5 cm), TD (FW = 5 cm), and IMRT. The HFRT-SIB prescription was administered as follows: a cumulative dose of 43.5 Gy was delivered to the planning target volume (PTV); a cumulative dose of 49.5 Gy was delivered to the planning gross target volume (PGTV). Results: For both the PGTV and PTV, the homogeneity index (HI) values were lowest with TD (FW = 2.5 cm). The conformity index (CI) values were highest with IMRT for both the PGTV and PTV. Mean target volume coverage met the requirements for the PGTV and PTV across TD with a FW of 2.5 cm, TD with a FW of 5 cm, and IMRT. For the left lung and heart, V5, V10, V20, V30, and the mean dose (Dmean) were the lowest with TD (FW = 2.5 cm). The maximum dose (Dmax) and Dmean for the left anterior descending coronary artery (LAD) were also lowest with TD (FW = 2.5 cm). TD (FW = 5 cm) provided slightly less protection for OARs than TD (FW = 2.5 cm). The average treatment time was 5 minutes for TD (FW = 5 cm) and 9 minutes for TD (FW = 2.5 cm). Conclusions: Compared with IMRT, TD provides better protection of cardiopulmonary function while maintaining target area quality. Overall, when employing TD for HFRT-SIB, a FW of 5 cm is recommended.

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