Is there a preferred IMRT technique for left-breast irradiation?

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Breath-hold radiotherapy is not universally available for left-breast irradiation.
• Intensity-modulated radiotherapy (IMRT) is explored for reducing heart doses.
• Limited long-term data exists for breast IMRT, necessitating caution regarding late toxicity.

Purpose of the Study:

• To compare four IMRT techniques for free-breathing left-breast irradiation.
• To prioritize organ at risk (OAR) sparing, mimicking tangent-based radiotherapy.
• To evaluate OAR sparing and planning target volume (PTV) coverage/homogeneity.

Main Methods:

• Ten simultaneous integrated boost treatment plans were created for left-breast irradiation.
• Four IMRT techniques were evaluated: hybrid-IMRT (H-IMRT), full IMRT (F-IMRT), and volumetric-modulated arc therapy with two (2ARC) and six (6ARC) partial arcs.
• Prioritization was given to reducing mean and low doses to organs at risk (heart, LAD+3 mm, lungs, contralateral breast).

Main Results:

• H-IMRT demonstrated superior mean and low dose OAR sparing and excellent PTV coverage (V95% = 98%) and homogeneity.
• H-IMRT delivered higher intermediate-high doses to the heart, LAD+3 mm, and ipsilateral lung.
• 6ARC and F-IMRT offered better intermediate-high dose sparing but resulted in increased dose to the contralateral breast/lung and compromised PTV coverage (V95% = 91-97%).

Conclusions:

• For left-breast irradiation without breath-hold, H-IMRT is the preferred technique when prioritizing mean and low dose sparing to organs at risk.
• H-IMRT is currently the standard approach at the institution for both free-breathing and breath-hold left-breast radiotherapy.
• Careful consideration of dose distribution trade-offs is essential when selecting IMRT techniques for breast cancer treatment.