gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Dosimetric Advantages of Protons for Partial Breast Irradiation

Meeting Abstract

  • J. Andrews - Radiation Oncology, Indiana University, Indianapolis, USA
  • C. Wai Cheng - Radiation Oncology, Midwest Proton Institute, Bloomington, USA
  • K. Kagawa - Radiation Oncology, West Osaka Hospital, Nishinomiya, Japan
  • I. Das - Radiation Oncology, Indiana University, Indianapolis, USA
  • P. Johnstone - Radiation Oncology, Indiana University, Indianapolis, USA

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog010

doi: 10.3205/09ptcog010, urn:nbn:de:0183-09ptcog0103

Published: September 24, 2009

© 2009 Andrews et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Specific aims: Provide a superior alternative treatment method with minimum co-morbidity for accelerated partial breast irradiation (APBI) of early stage breast cancer with proton beam.

Background and significance: Approximately 50% of all local breast recurrences occur in or near the site of the original tumor, and half occur elsewhere in the breast. Over the last decade, APBI has become an accepted treatment modality, although data on long-term outcomes are not yet available. The main advantage of APBI is the significantly shortened treatment time. Another potential advantage is that smaller volumes of normal tissue would be impacted – in particular, the heart and lung volumes -- which may lead to fewer complications.

A variety of methods of delivery for partial breast irradiation include external beam radiotherapy using either 3D Conformal or Intensity modulated (IMRT) technique; soft x-rays device (XOFT); intraoperative therapy; and intracavitary brachytherapy (Mammosite and Contoura). These different approaches are all widely used; randomized trials are ongoing to determine the merit of each system. The dose distribution of protons as compared to other forms of radiation are far superior in depth dose ability to spare normal tissue. The spread out Bragg Peak (SOBP) can be tailored to each patient and provide enhanced dose distribution in APBI patients. Proton beams have unique physical characteristics that could be also be used for APBI which is presented here.

Methods: The dosimetry of 20 breast patients treated per the APBI RTOG protocol were evaluated. A CMS treatment planning system for dosimetric comparison was evaluated for target coverage and the dose to organs at risk (OAR) . Comparisons between photons, protons and electrons were established to assess the PTV dose, treated breast dose at 20Gy, lung and heart dose at 20Gy. Patients were separated based on their large or small breast volume (Figure 1 [Fig. 1]).

Results: Proton APBI has shown a decrease in the amount of normal tissue receiving 50% of the prescribed dose by 36%. The purpose of this dosimetric study is to establish the superiority for the clinical application of proton APBI compared to current methods of delivery. Table 1 [Tab. 1] shows the data for PTV and OAR for proton beam, indicating minimum to no dose to OAR.

Conclusion: The PTV dose did not differ significantly for the different treatment modalities (photon, electron and protons). Photons demonstrated a larger volume of breast receiving 20Gy in the large breasted group. Dose to the lung and heart at 20Gy were comparable for all three treatment modalities. This dosimetric comparison establishes that protons may be a superior option for partial breast irradiation.