Radiation therapy planning with photons and protons for early and advanced breast cancer: an overview

Abstract

Postoperative radiation therapy substantially decreases local relapse and moderately reduces breast cancer mortality, but can be associated with increased late mortality due to cardiovascular morbidity and secondary malignancies. Sophistication of breast irradiation techniques, including conformal radiotherapy and intensity modulated radiation therapy, has been shown to markedly reduce cardiac and lung irradiation. The delivery of more conformal treatment can also be achieved with particle beam therapy using protons. Protons have superior dose distributional qualities compared to photons, as dose deposition occurs in a modulated narrow zone, called the Bragg peak. As a result, further dose optimization in breast cancer treatment can be reasonably expected with protons. In this review, we outline the potential indications and benefits of breast cancer radiotherapy with protons. Comparative planning studies and preliminary clinical data are detailed and future developments are considered.

Figure 1

Cumulative dose-volume histograms for the conventional photon (Conventional), the intensity modulated treatment (IMRT 1–2) and the proton (Protons) plans for the breast and the breast and regional lymph nodes [33].

Figure 2a

Cumulative dose-volume histograms for the conventional photon (Conventional), the intensity modulated treatment (IMRT 1–2) and theproton (Protons) plans for the heart [33]. (B) Cumulative dose-volume histograms for the conventional photon (Conventional), the intensity modulated treatment (IMRT 1–2) and the proton (Protons) plans for the ipsilateral lung [33].

Figure 3

Dose distribution (protons) in an axial CT slice through the center of the breast for an early breast cancer patient treated with partial breast irradiation. The isodose contours are represented by different colors (corresponding values are displayed on the upper-right border of the figure).