2D Planning for Breast Cancer Radiotherapy with Wedges
Direct Recommendation
For 2D planning of breast cancer radiotherapy, use wedges (15°, 30°, or 45°) as compensators to achieve uniform dose distribution and minimize normal tissue toxicity, with wedge angle selection based on breast contour and size to optimize target homogeneity. 1
Technical Implementation
Wedge Selection Strategy
Wedge angles of 15°, 30°, 45°, and 60° can all be used for breast radiotherapy, with selection based on individual breast anatomy and the need for dose homogeneity 2, 3
30° wedges are most commonly employed for standard breast contours, while 15° wedges suit flatter breast profiles and 45° wedges accommodate more pendulous breasts 2
The goal is to achieve uniform dose distribution throughout the breast tissue while minimizing hot spots 1
Planning Approach
CT-based treatment planning is strongly encouraged to delineate target volumes and identify organs at risk (heart and lungs) 1, 4
Use tangential beam arrangements with wedges as compensators to accomplish greater target dose homogeneity and normal tissue sparing 1
Ensure no more than 3-3.5 cm of lung is included in the treatment field, with a minimum of 1-1.5 cm required 4, 5
Dosimetric Considerations
Standard whole breast dose: 45-50 Gy in 23-25 fractions (1.8-2.0 Gy per fraction) or the preferred hypofractionated regimen of 40-42.5 Gy in 15-16 fractions 1, 4
Tumor bed boost of 10-16 Gy in 4-8 fractions is recommended for high-risk patients (age <50 years, high-grade disease, or focally positive margins) 1, 4
Comparison of Wedge Techniques
Physical Wedges vs. Enhanced Dynamic Wedges
Enhanced dynamic wedges (EDW) produce less scattered dose to structures outside the treatment field compared to physical wedges, potentially reducing second malignancy risk 3
EDW requires fewer monitor units to deliver the same dose due to different wedge factors 3
Maximum dose within the target volume tends to be slightly higher with EDW, but planning target volume conformity index remains equivalent 3
Wedge Technique Limitations
Traditional wedge techniques produce higher volumes receiving ≥107% of prescription dose (V107: 7.5%±4.2%) compared to more modern techniques like field-in-field or IMRT 2, 6
Forward-planned IMRT with multiple MLC-shaped segments produces smaller global hot spots and more evenly distributed dose compared to conventional wedge techniques across all breast sizes 2
Critical Pitfalls to Avoid
Never exceed 3-3.5 cm of lung in the treatment field to prevent radiation pneumonitis 4, 5
Minimize cardiac irradiation, particularly for left-sided breast cancers, as techniques resulting in cardiac exposure increase late cardiac mortality 4, 5
Avoid overlap between adjacent fields to prevent hot spots 4
Use bolus material when photon fields are employed to ensure adequate skin dose for chest wall treatments 1