This review summarizes the past and present status of
proton beam therapy (PBT) for
lung cancer. PBT has a unique characteristic called the Bragg peak that enables a reduction in the dose of normal tissue around the
tumor, but is sensitive to the uncertainties of density changes. The heterogeneity in electron density for thoracic lesions, such as those in the lung and mediastinum, and
tumor movement according to respiration necessitates respiratory management for PBT to be applied in
lung cancer patients. There are two types of PBT - a passively scattered approach and a scanning approach. Typically, a passively scattered approach is more robust for respiratory movement and a scanning approach could result in a more conformal dose distribution even when the
tumor shape is complex. Large
tumors of centrally located
lung cancer may be more suitably irradiated than with
intensity-modulated radiotherapy (IMRT) or stereotactic body radiotherapy (SBRT). For a locally advanced
lung cancer, PBT can spare the lung and heart more than photon IMRT. However, no randomized controlled trial has reported differences between PBT and IMRT or SBRT for early-stage and locally advanced
lung cancers. Therefore, a well-designed controlled trial is warranted.