title: Dosimetric trade-offs in breast treatment with VMAT technique.
abstract: OBJECTIVE
  Breast planning with volumetric modulated arc therapy (VMAT) has been explored, especially for left-sided breast treatments, with the primary intent of lowering the heart dose and improving target dose homogeneity. As a trade-off, larger healthy tissue volumes would receive low dose levels, with the potential risk of increasing late toxicities and secondary cancer induction, although no clinical data are available today to confirm the risk level. The scope of this work is to explore the dosimetric trade-offs using two different VMAT plans.
  
  
  METHODS
  Two planning strategies for dual-partial-arc VMAT, RA_avoid and RA_full, with and without avoidance sectors, were explored in a cohort of 20 patients, for whole left breast irradiation for 40.05 Gy to the mean target dose in 15 fractions. Common dose objectives included a stringent dose homogeneity, mean dose to the heart <5 Gy, ipsilateral lung (Ilung) <8 Gy, contralateral lung (Clung) <2 Gy and contralateral breast (Cbreast) <3 Gy.
  
  
  RESULTS
  RA_full showed a better dose conformity, lower high-dose spillage in the healthy tissue and lower skin dose. RA_avoid presented a reduction of the mean doses for all critical structures: 51% to the heart, 12% to the Ilung, 81% to the Clungand 73% to the Cbreast. All differences were significant with p < 0.0001.
  
  
  CONCLUSIONS
  The adaptation of VMAT options to planning objectives reduced significantly the healthy tissue dose levels at the price of some high-dose spillage. Evaluation of the trade-offs for application to the different critical structures should drive in improving the usage of the VMAT technique for breast cancer treatment. Advances in knowledge: Different planning strategies in the same VMAT technique could give significant variations in dose distributions. The choice of the trade-offs would affect the possible future late toxicity and secondary cancer induction risk.
authors.affiliation: 1 Radiotherapy and Radiosurgery Department, Humanitas Research Hospital and Cancer Center, Milan-Rozzano, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Fogliata
authors.affiliation: 2 Radiotherapy Department, Cancer Center, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Jan
authors.initials: J
authors.lastname: Seppälä
authors.affiliation: 1 Radiotherapy and Radiosurgery Department, Humanitas Research Hospital and Cancer Center, Milan-Rozzano, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Reggiori
authors.affiliation: 1 Radiotherapy and Radiosurgery Department, Humanitas Research Hospital and Cancer Center, Milan-Rozzano, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Lobefalo
authors.affiliation: 1 Radiotherapy and Radiosurgery Department, Humanitas Research Hospital and Cancer Center, Milan-Rozzano, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Palumbo
authors.affiliation: 1 Radiotherapy and Radiosurgery Department, Humanitas Research Hospital and Cancer Center, Milan-Rozzano, Italy.
authors.forename: Fiorenza
authors.initials: F
authors.lastname: De Rose
authors.affiliation: 1 Radiotherapy and Radiosurgery Department, Humanitas Research Hospital and Cancer Center, Milan-Rozzano, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Franceschini
authors.affiliation: 1 Radiotherapy and Radiosurgery Department, Humanitas Research Hospital and Cancer Center, Milan-Rozzano, Italy.|3 Biomedical Science Department, Humanitas University, Milan-Rozzano, Italy.
authors.forename: Marta
authors.initials: M
authors.lastname: Scorsetti
authors.affiliation: 1 Radiotherapy and Radiosurgery Department, Humanitas Research Hospital and Cancer Center, Milan-Rozzano, Italy.|3 Biomedical Science Department, Humanitas University, Milan-Rozzano, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Cozzi
mesh_terms: D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods* / Q000706:statistics & numerical data*