title: Planning hybrid intensity modulated radiation therapy for whole-breast irradiation.
abstract: OBJECTIVE
  To test tangential and not-tangential hybrid intensity modulated radiation therapy (IMRT) for whole-breast irradiation.
  
  
  METHODS
  Seventy-eight (36 right-, 42 left-) breast patients were randomly selected. Hybrid IMRT was performed by direct aperture optimization. A semiautomated method for planning hybrid IMRT was implemented using Pinnacle scripts. A plan optimization volume (POV), defined as the portion of the planning target volume covered by the open beams, was used as the target objective during inverse planning. Treatment goals were to prescribe a minimum dose of 47.5 Gy to greater than 90% of the POV and to minimize the POV and/or normal tissue receiving a dose greater than 107%. When treatment goals were not achieved by using a 4-field technique (2 conventional open plus 2 IMRT tangents), a 6-field technique was applied, adding 2 non tangential (anterior-oblique) IMRT beams.
  
  
  RESULTS
  Using scripts, manual procedures were minimized (choice of optimal beam angle, setting monitor units for open tangentials, and POV definition). Treatment goals were achieved by using the 4-field technique in 61 of 78 (78%) patients. The 6-field technique was applied in the remaining 17 of 78 (22%) patients, allowing for significantly better achievement of goals, at the expense of an increase of low-dose (∼5 Gy) distribution in the contralateral tissue, heart, and lungs but with no significant increase of higher doses (∼20 Gy) in heart and lungs. The mean monitor unit contribution to IMRT beams was significantly greater (18.7% vs 9.9%) in the group of patients who required 6-field procedure.
  
  
  CONCLUSIONS
  Because hybrid IMRT can be performed semiautomatically, it can be planned for a large number of patients with little impact on human or departmental resources, promoting it as the standard practice for whole-breast irradiation.
authors.affiliation: Medical Physics Department, Regional Oncological Hospital, Cagliari, Italy. paolofarace@gmail.com
authors.forename: Paolo
authors.initials: P
authors.lastname: Farace
authors.forename: Sergio
authors.initials: S
authors.lastname: Zucca
authors.forename: Ignazio
authors.initials: I
authors.lastname: Solla
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Fadda
authors.forename: Silvia
authors.initials: S
authors.lastname: Durzu
authors.forename: Sergio
authors.initials: S
authors.lastname: Porru
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Meleddu
authors.forename: Maria Assunta
authors.initials: MA
authors.lastname: Deidda
authors.forename: Marco
authors.initials: M
authors.lastname: Possanzini
authors.forename: Sivia
authors.initials: S
authors.lastname: Orrù
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Lay
mesh_terms: D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D047368:Tumor Burden