title: Prone accelerated partial breast irradiation after breast-conserving surgery: compliance to the dosimetry requirements of RTOG-0413.
abstract: OBJECTIVE
  The dosimetric results from our institution's trials of prone accelerated partial breast irradiation are compared with the dosimetric requirements of RTOG-0413.
  
  
  METHODS
  Trial 1 and Trial 2 are 2 consecutive trials of prone-accelerated partial breast irradiation. Eligible for both trials were stage I breast cancer patients with negative margins after breast-conserving surgery. The planning target tumor volume (PTV) was created by extending the surgical cavity 2.0 cm for Trial 1 and 1.5 cm for Trial 2, respectively. Contralateral breast, heart, lungs, and thyroid were contoured. Thirty Gray was delivered in five daily fractions of 6 Gy by a three-dimensional conformal radiation therapy technique in Trial 1 and were by image-guided radiation therapy/intensity-modulated radiation therapy in Trial 2. Dosimetric results from the trials are reported and compared with RTOG 0413 requirements.
  
  
  RESULTS
  One hundred forty-six consecutive plans were analyzed: 67 left and 79 right breast cancers. The plans from the trials complied with the required>90% of prescribed dose covering 90% of PTV_EVAL (=generated from the PTV by cropping 0.5 cm from the skin edge and excluding the chest wall): V90% was 98.1±3.0% (with V100% and V95%, 89.4±12.8%, 96.4±5.1%, respectively). No significant difference between laterality was found (Student's t test). The dose constraints criteria of the RTOG-0413 protocol for ipsilateral and contralateral lung (V30<15% and Dmax<3%), heart (V5<40%), and thyroid (Dmax<3%) were satisfied because the plans showed an average V5% of 0.6% (range, 0-13.4) for heart, an average V30% of 0.6% (range, 0-9.1%) for ipsilateral lung, and <2% maximum dose to the thyroid. However, our partial breast irradiation plans demonstrated a higher dose to contralateral breast than that defined by RTOG constraints, with a median value of maximum doses of 4.1% (1.2 Gy), possibly as a result of contouring differences.
  
  
  CONCLUSIONS
  Our technique for prone accelerated partial breast irradiation generally satisfied RTOG-0413 requirements.
authors.affiliation: Department of Radiation Oncology, New York University Medical Center, New York, New York 10016, USA.
authors.forename: Bixiu
authors.initials: B
authors.lastname: Wen
authors.forename: Howard
authors.initials: H
authors.lastname: Hsu
authors.forename: George F
authors.initials: GF
authors.lastname: Formenti-Ujlaki
authors.forename: Stella
authors.initials: S
authors.lastname: Lymberis
authors.forename: Chiara
authors.initials: C
authors.lastname: Magnolfi
authors.forename: Xuan
authors.initials: X
authors.lastname: Zhao
authors.forename: Jenghwa
authors.initials: J
authors.lastname: Chang
authors.forename: J Keith
authors.initials: JK
authors.lastname: DeWyngaert
authors.forename: Gabor
authors.initials: G
authors.lastname: Jozsef
authors.forename: Silvia C
authors.initials: SC
authors.lastname: Formenti
mesh_terms: D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D019583:Dose Fractionation, Radiation; D005260:Female; D006321:Heart / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000528:radiation effects; D015412:Mastectomy, Segmental; D009068:Movement; D058958:Organs at Risk / Q000528:radiation effects*; D056888:Patient Positioning / Q000379:methods*; D016684:Prone Position; D011446:Prospective Studies; D018714:Radiotherapy, Adjuvant / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods*; D012119:Respiration; D013961:Thyroid Gland / Q000528:radiation effects; D047368:Tumor Burden