Quantifying dose to the reconstructed breast: can we adequately treat?

Area of Science:

• Oncology
• Radiotherapy
• Plastic Surgery

Background:

• Immediate breast reconstruction (IR) is increasingly common after mastectomy.
• Understanding the impact of IR on postmastectomy radiotherapy (PMRT) is crucial for optimizing treatment planning and outcomes.
• Dosimetric evaluation is essential to quantify the effects of different reconstruction techniques on radiation dose distribution.

Purpose of the Study:

• To evaluate how immediate reconstruction (IR) affects postmastectomy radiotherapy (PMRT) dose distributions to the reconstructed breast (RB), internal mammary nodes (IMN), heart, and lungs.
• To compare dosimetric endpoints between autologous reconstruction (AR) and expander-implant (EI) techniques.
• To assess the influence of laterality and internal mammary node (IMN) coverage on radiation dose to critical organs.

Main Methods:

• Developed 3D conformal plans for 20 IR patients (10 AR, 10 EI), with 5 right- and 5 left-sided reconstructions per type.
• Created two plans per patient: RB coverage alone and RB + IMN coverage.
• Quantified dosimetric endpoints including Dmean and D95 for RB and IMN, and heart and lung doses.

Main Results:

• Reconstructed breast (RB) coverage was adequate in all cases (Dmean 50.61 Gy, D95 45.76 Gy).
• Internal mammary node (IMN) coverage achieved Dmean of 49.57 Gy and D95 of 40.96 Gy when included.
• Left-sided expander-implant (EI) plans without IMN coverage showed higher heart Dmean (2.97 Gy) compared to left-sided autologous reconstruction (AR) plans (0.84 Gy, p=0.03).
• Mean heart doses increased with left-sided treatment and IMN inclusion; mean lung V(20) increased with right-sided treatment and IMN inclusion.

Conclusions:

• Immediate reconstruction (IR) allows for adequate dose delivery to the reconstructed breast (RB) and internal mammary nodes (IMN) during postmastectomy radiotherapy (PMRT).
• Reconstruction type (AR vs. EI) generally had minimal impact on dose distribution, with a noted exception for heart dose in left-sided EI cases.
• Standard 3D planning techniques provide excellent coverage of the RB and IMN, irrespective of laterality or reconstruction method.