Optimizing Left-Sided Breast Cancer Radiotherapy: Strategy-Dependent Trade-Offs Among VMAT and Hybrid Techniques.

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Planning

Background:

• Left-sided whole-breast irradiation (WBI) presents challenges in sparing organs at risk.
• Volumetric Modulated Arc Therapy (VMAT) and 3D-Conformal Radiation Therapy (3D-CRT) are common techniques.
• Optimizing dosimetric trade-offs is crucial for minimizing toxicity.

Purpose of the Study:

• To compare dosimetric trade-offs between full-VMAT and hybrid 3D-CRT/VMAT strategies for left-sided WBI.
• To evaluate the influence of planning strategy on dosimetric outcomes.
• To introduce and assess a novel tangential hybrid approach (H-tVMAT).

Main Methods:

• Retrospective analysis of 20 patients with left-sided breast cancer undergoing WBI.
• Generation of four treatment plans per patient: large-angle VMAT, tangential VMAT (tVMAT), Hybrid VMAT (H-VMAT), and H-tVMAT.
• Evaluation of primary dosimetric endpoints including heart, pulmonary structures, contralateral breast, low-dose exposure, target conformity, homogeneity index, and monitor units.

Main Results:

• All strategies achieved acceptable target coverage and homogeneity.
• Hybrid configurations demonstrated reduced cardiac, pulmonary, and contralateral low-dose exposure compared to full-VMAT.
• H-tVMAT provided the most favorable balance of organ sparing, low-dose containment, and target coverage; optimized tVMAT showed comparable results.

Conclusions:

• Dosimetric performance in left-sided WBI is highly dependent on planning implementation, not just the technique category.
• Hybrid tangential VMAT offers the most balanced dosimetric profile.
• A strategy-specific approach to technique selection, emphasizing implementation choices, is recommended for breast radiotherapy planning.