Background: Synchronous malignancy in both breasts is a rare incidence. The present study aims at dosimetric comparison of intensity-modulated radiation therapy(IMRT), volumetric modulated arc therapy(VMAT) and intensitiy modulated proton therapy(IMPT) for patients with synchronous bilateral breast cancer(SBBC).
Methods: For 8 patients with synchronous bilateral breast ,three plans were designed : IMRT (4-6 fields with double isocenters), VMAT (8 partial arcs with double isocenters) and IMPT(2 fields with a single isocenter). Plans were designed to achieve 95% coverage of target to a dose of 50 Gy or Gy (RBE) while maximally sparing organs-at-risk.The plans were evaluated based on a dose-volume histogram analysis.
Results: For PTV, IMPT plans showed the best max dose (D2%) and homogeneity. VMAT plans showed the best conformity.Compared to IMRT and VMAT plans, IMPT plans significantly reduced V5,V10 and mean dose to lungs.VMAT plans showed the highest values on V5,V10 of lungs.IMPT plans significantly reduced V5,V10,V20,V30,V40 and mean dose to heart.Compared to IMRT and VMAT plans, IMPT plans significantly reduced V5,V10,V20,V30 and mean dose to left anterior descending and left ventricle.
Conclusions: IMPT plans improved homogeneity to the target and reduced doses to the lungs and heart.