Peter A. S. Johnstone, MD

The role of radiation therapy (RT) in lung cancer is long established; some of the earliest Radiation Therapy Oncology Group reports dealt with non-small cell lung cancer (NSCLC).[1,2] More recently, the advent of stereotactic body RT (SBRT) techniques has provided significant local control rates after focused treatment of selected small metastases and inoperable early stage lesions.[3,4] Our center has been in the forefront of examining SBRT and its role in central [5] or bilateral [6] lesions, its effect on PET imaging [7] and pulmonary function testing,[8] and subsequent frequency of brachial plexopathy,[9] chest wall toxicity,[10] or pneumonitis.[11] Still, even this highly conformal technique comes with potentially significant dose to adjacent normal tissue. This is in the context of an emerging appreciation for the pulmonary consequences of elevated mean lung dose,[12] or V5 after pneumonectomy.[13] For each lung cancer patient requiring RT, an effective mechanism to deliver dose to the tumor while minimizing dose to uninvolved lung is called for. Enter protons.