Evaluation of coplanar partial left breast irradiation using tomotherapy-based topotherapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Breast Cancer Treatment

Background:

• Accelerated partial breast irradiation (APBI) is an alternative to whole-breast irradiation.
• Conventional techniques include 3D-CRT and IMRT.
• Topotherapy offers intensity modulation and precise beam delivery.

Purpose of the Study:

• To evaluate topotherapy for APBI.
• To optimize field arrangements for topotherapy.
• To compare topotherapy dosimetrically with 3D-CRT and IMRT.

Main Methods:

• Contouring of 3-cm lumpectomy sites in a hypothetical breast.
• Optimization of coplanar intensity-modulated topotherapy plans (2-7 fields).
• Comparison with noncoplanar five-field 3D-CRT and IMRT plans.

Main Results:

• Topotherapy achieved excellent target coverage (99.5% +/- 0.5% of prescription dose).
• Low doses to heart (1.20-2.06 Gy) and lungs (0.79-1.76 Gy ipsilateral, 0.10-0.29 Gy contralateral).
• Five-field plans minimized normal breast and skin dose; uniformity was comparable across techniques.

Conclusions:

• Coplanar partial breast topotherapy provides effective target coverage and minimal organ-at-risk dose.
• More than five fields offered no dosimetric advantage.
• Topotherapy demonstrated equivalent target conformality and uniformity to 3D-CRT and IMRT for APBI.