Debate 1: For Proton SBRT
Proton SBRT is ready to move past uncertainties and towards improved clinical outcomes
Charles B. Simone, II and Liyong Lin
Stereotactic body radiation therapy (SBRT) is adopted as an effective treatment option for most early stage and some locally advanced cancers [1-2], with treatment planning, delivery and quality assurance guidelines well established [3]. SBRT, as has historically been delivered with photon therapy, becomes increasingly difficult to deliver when tumor becomes more locally advanced in size (>5 cm) or centrally located near critical structures, especially for lung and liver tumors, as surrounding normal tissue toxicities can become prohibitive [4-5]. Toxicities from low dose (<5 Gy) irradiation during photon SBRT, including lymphopenia and loss of remaining liver or lung function, can often be completely eliminated with stereotactic body proton therapy (SBPT) [6-8] because of essentially zero exit dose for proton beams beyond a fixed depth, the practical range of maximum incoming proton energy. Limited proton range makes SBRT highly advantageous for some central lung and liver tumors when critical organs at risks (OARs) are located beyond proton range uncertainty. Such SBPT advantages make it the treatment of choice for reirradiation and for patients with significantly preexisting liver or lung dysfunction.
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