Physical and Biological Aspects of 3-dimensional Conformal and Intensity Modulated Radiotherapy Techniques for Treating Left-Sided Breast Cancer

Purpose:
This study focused on evaluating how 3D Conformal Radiotherapy (3D-CRT) and Intensity-Modulated Radiotherapy (IMRT) are used to treat left-sided breast cancer in patients who previously underwent breast-conserving surgery. These radiotherapy techniques aim to eliminate residual cancer cells while protecting nearby organs (the heart and lungs). Given the proximity of the heart to the left breast, minimizing long-term cardiac and pulmonary complications was a key goal of this research.
Methods:
For 16 patients, the study compared biological and dosimetric parameters to assess the performance of each technique. Biological metrics (EUD, TCP, and NTCP) were calculated using a MATLAB program, while dosimetric indices (HI and CI) and dose-volume parameters were derived from DVH analysis. Parameters included: (V95%, V107%, Dmax, Dmean, Dmin) for PTV; (V20%, Dmax, Dmean, Dmin) for both lungs; and (V30%, Dmax, Dmean, Dmin) for the heart.
Results:
IMRT demonstrated significantly improved tumor control within the PTV, with higher and more consistent TCP values. It also outperformed 3D-CRT in conformity and homogeneity indices, offering a more uniform and accurate dose distribution. DVH analysis showed IMRT provided a higher minimum and mean dose to the PTV, though the Dmax difference was not significant. Both techniques were safe for the heart, but IMRT delivered a higher EUD, raising concern for potential cardiac risks. Both lungs were adequately protected; NTCP for the left lung was slightly lower and more stable with 3D-CRT.
Conclusions:
IMRT showed superior accuracy and uniformity in dose delivery compared to 3D-CRT, potentially enhancing treatment efficacy and patient outcomes.