We are witnessing a new era in proton therapy research, with an unprecedented number of clinical studies under way. For three decades, research has focused heavily on pediatric tumors and tumors of the brain, spine and prostate, establishing that proton therapy is efficacious, enables precise targeting of tumors permitting higher doses of radiation with few short- and long-term side effects, and maintains a high quality of life for patients.[1-9] The treatment also has been shown to reduce the likelihood of treatment-related malignancies.[10] Researchers now are exploring the clinically meaningful benefit of proton therapy in diseases of high incidence, particularly lung and breast cancer, where the precision and limited side effects can provide effective treatment with significant long-term benefit to the patient. Initial results prove hopeful, especially for lung cancer, which remains the No. 1 cancer killer of both men and women.[11]