Proton radiotherapy for breast cancer

Proton therapy can be advantageous for select patients with breast cancer. Cases with “complex geometry,” including postmastectomy cases, implants, body habitus, or depth of targets, can lead to unacceptably high doses to normal tissues when photon/electron-based techniques are used. In these cases, protons can provide excellent conformality with clinically meaningful reductions in the nontarget dose. In early-stage breast cancer patients who are appropriate candidates for partial breast irradiation, the beam characteristics for protons can similarly reduce the dose to the nontarget breast and the conformality of a catheter-based solution without the disadvantages of placing and maintaining a catheter. Additional theoretical advantages to reduce dose to the shoulder girdle and back, as well as the heart and nontarget lymph nodes, are actively being studied. In all cases, setup and immobilization factors are critical.