Current developments in proton therapy: a review.

The use of high-energy protons in radiotherapy was first proposed in 1946. In the last decade there has been a significant growth in the number of centres using protons in the treatment of malignant and non-malignant disease. To date (January 1993) a total of more than 11,500 patients have been treated world-wide. Encouraging clinical results have been reported in the literature. The purpose of this article is to outline the advantages of proton beams and to review current developments in physics and engineering applied to the field of proton therapy with particular emphasis on proton accelerator technology and the development of proton therapy facilities. The production of clinically useful beams is discussed and the relative merits of different treatment systems compared. Reference is also made to the factors affecting the absorbed dose in a patient and to proton radiobiology together with the results of studies of comparisons of treatment planning with protons with that using conventional photon therapy. The dosimetry of proton beams is also reviewed.