Comprehensive nodal breast VMAT: solving the low-dose wash dilemma using an iterative knowledge-based radiotherapy...

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Developing efficient Volumetric Modulated Arc Radiotherapy (VMAT) for comprehensive lymph node (CLN) breast cancer is crucial.
• Minimizing low-dose bath is essential to reduce risks of secondary malignancies.

Purpose of the Study:

• To develop and validate a simple, robust knowledge-based planning (KBP) VMAT approach for CLN breast cancer.
• To assess if this approach can achieve target coverage and organ-at-risk (OAR) sparing without increasing low-dose wash.

Main Methods:

• A KBP VMAT model was developed using 40 CLN breast patient datasets.
• The model was validated against hybrid-VMAT and bowtie-VMAT using 20 additional datasets.
• Evaluated parameters included planning target volume (PTV) coverage, conformity/homogeneity index (CI/HI), OAR sparing, and radiation oncologist preference.

Main Results:

• The KBP-generated ipsilateral-VMAT (ipsi-VMAT) plans were dosimetrically equivalent to bowtie-VMAT and superior to hybrid-VMAT in nodal target coverage.
• Improved dose sparing to the ipsilateral lung and humeral head was observed with ipsi-VMAT.
• Low-dose wash to OARs and remaining-volume-at-risk (RVR) were comparable across all tested VMAT techniques.

Conclusions:

• A simple and robust ipsilateral VMAT class solution for CLN breast cancer was successfully developed using iterative KBP modeling.
• This approach achieves clinically acceptable target coverage and OAR sparing without increasing low-dose wash, thus not elevating the risk of second malignancies.