Fundamental Biophysical Aspects of High‐energy Radiations in Cancer Therapy*

The limitations of conventional therapy with x and γ radiations are reported, and high‐energy particulate radiations that exhibit physical and/or biological properties more suitable for cancer therapy are discussed. Specifically, future prospects for radiotherapy with beams of electrons, neutrons, negative pions, protons, α particles, and heavy ions are surveyed, and some of the results of clinical trials are analyzed. According to the American Cancer Society there are now over half a million new cancer patients in the United States each year. At the present cure rate, approximately half of these patients can be expected to eventually die of their disease, and almost one‐third of these deaths will be due to noncontrol of the localized primary tumor. It is with this group of roughly 100,000 patients per year that new approaches to radiotherapy will probably be most productive.