Prone accelerated partial breast irradiation after breast-conserving surgery: compliance to the dosimetry requirements of RTOG-0413

Int J Radiat Oncol Biol Phys. 2012 Nov 15;84(4):910-6. doi: 10.1016/j.ijrobp.2012.01.055. Epub 2012 Apr 28.


Purpose: The dosimetric results from our institution's trials of prone accelerated partial breast irradiation are compared with the dosimetric requirements of RTOG-0413.

Methods and materials: 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.

Publication types

  • Clinical Trial
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Breast / radiation effects
  • Breast Neoplasms / radiotherapy*
  • Breast Neoplasms / surgery
  • Dose Fractionation, Radiation
  • Female
  • Heart / radiation effects
  • Humans
  • Lung / radiation effects
  • Mastectomy, Segmental
  • Movement
  • Organs at Risk / radiation effects*
  • Patient Positioning / methods*
  • Prone Position
  • Prospective Studies
  • Radiotherapy, Adjuvant / methods
  • Radiotherapy, Conformal / methods*
  • Respiration
  • Thyroid Gland / radiation effects
  • Tumor Burden