TITLE:
A Comparative Dosimetric and Radiobiological Analysis of 3DCRT, IMRT, and VMAT for Left-Sided Breast Cancer Radiotherapy
AUTHORS:
Aliaa Mahmoud, Wahib Mohamed Attia, Ehab Marouf Attalla, Hany Samy Attallah
KEYWORDS:
Breast Cancer, Intensity-Modulated Radiotherapy, Volumetric Modulated Arc Therapy, Dosimetric Comparison
JOURNAL NAME:
Advances in Breast Cancer Research,
Vol.15 No.1,
December
31,
2025
ABSTRACT: Background: Breast cancer is the most common malignancy in women, and adjuvant radiotherapy for left-sided disease raises important concerns regarding cardiac and pulmonary toxicity. Advanced techniques such as intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) may improve dose conformity compared with three-dimensional conformal radiotherapy (3DCRT), but can increase low-dose exposure to normal tissues. Methods: In this retrospective planning study, three techniques—3DCRT, IMRT, and VMAT—were compared for left-sided whole-breast irradiation using both conventional dosimetric metrics and Equivalent Uniform Dose (EUD)-based radiobiological modeling, where EUD represents the biologically equivalent uniform dose corresponding to a heterogeneous dose distribution. Sixteen women with left-sided breast cancer treated at a single institution underwent CT simulation and had three separate plans generated on the same dataset (3DCRT, IMRT, VMAT) with identical prescription dose and uniform dose-volume constraints. Planning target volume (PTV) indices and organs-at-risk (OAR) doses were extracted from dose-volume histograms. Tumor control probability (TCP) and normal tissue complication probability (NTCP) for the heart, ipsilateral and contralateral lungs, and contralateral breast were calculated using Niemierko-based EUD models. Results: PTV coverage, minimum dose, and 107% hot-spot volume did not differ significantly among the three techniques, indicating comparable target coverage. VMAT produced significantly higher low-dose cardiac exposure (Heart V10), whereas mean heart dose and Heart V25 were similar across techniques. Ipsilateral lung mean dose and V20 were broadly comparable, with only modest, non-significant numerical differences between modalities. VMAT yielded significantly higher maximum doses to the contralateral lung and contralateral breast compared with 3DCRT, while mean doses to these structures remained similar. Radiobiological modeling showed no significant difference in TCP between techniques; however, NTCP estimates for the heart and ipsilateral lung were lower with IMRT and VMAT than with 3DCRT, whereas NTCP for contralateral structures did not differ significantly. Conclusion: IMRT and VMAT offer radiobiological advantages for modeled cardiac and pulmonary toxicity compared with 3DCRT, while maintaining comparable target coverage, but VMAT is associated with a broader low-dose bath to contralateral structures. These exploratory findings support individualized technique selection that balances target coverage, organ-at-risk sparing, and long-term survivorship considerations in left-sided breast radiotherapy.