Dosimetric Comparison of Intensity Modulated Radiotherapy (IMRT) and 3DCRT Field-in-Field (FIF) Planning Techniques for Left Breast Carcinoma Treatment
Authors: Nahida Sultana
Institution: Square Hospitals Limited
Introduction
Radiotherapy plays a vital role in the management of left-sided breast carcinoma, where achieving optimal target coverage while minimising radiation exposure to adjacent organs at risk (OARs), particularly the heart and ipsilateral lung, remains a major clinical challenge. Deep Inspiration Breath Hold (DIBH) is an advanced respiratory motion management technique that increases the distance between the heart and the chest wall during treatment, thereby reducing cardiac exposure. In addition, DIBH selecting an appropriate radiotherapy planning technique is crucial for achieving optimal target coverage, dose homogeneity and conformity while minimising radiation exposure to organs at risk (OARs).
Methods
Treatment plans were generated and evaluated using the Varian Eclipse Treatment Planning System (version 18.0) for a Varian TrueBeam linear accelerator (version 03), equipped with a 120-leaf Millennium dynamic multi-leaf collimator (MLC). IMRT plans were developed using 6-MV photon beams, whereas 3DCRT-FIF plans were generated using 10-MV photon beams with a 0.5-cm bolus. DIBH was incorporated during treatment planning to facilitate cardiac sparing and reduce irradiation of adjacent normal tissues. The dosimetric comparisons were performed by evaluating the Planning Target Volume (PTV) dose distribution, Homogeneity Index (HI) and Conformity Index (CI).
Results
The dosimetric evaluation demonstrated that IMRT provided superior target dose homogeneity and conformity compared with 3DCRT-FIF. The average HI was 0.008 for IMRT compared with 0.082 for 3DCRT-FIF, indicating a more homogeneous dose distribution with IMRT. Similarly, the average CI was 1.022 for IMRT and 1.181 for 3DCRT-FIF, demonstrating better conformity of the prescribed dose to the target volume with IMRT. The mean heart dose was 3.79 Gy with DIBH, while the ipsilateral lung V20 was 19.05%. These findings highlight the importance of incorporating DIBH into left-sided breast radiotherapy to facilitate cardiac protection while maintaining adequate target coverage. However, a direct comparison of heart and lung dose parameters between the two planning techniques is required to establish their relative OAR-sparing performance.
Conclusion
The findings indicate that IMRT provides better target dose homogeneity and conformity than 3DCRT-FIF for left-sided breast carcinoma. The incorporation of DIBH represents an important strategy for reducing cardiac exposure during left breast irradiation. The combination of advanced radiotherapy planning and DIBH may contribute to improved treatment quality by balancing target coverage with normal tissue protection.