Results of heavy ion radiotherapy.

The potential of heavy ion therapy for clinical use in cancer therapy stems from the biological parameters of heavy charged particles and their precise dose localization. Biologically, carbon, neon, and other heavy ion beams (up to about silicon) are clinically useful in overcoming the radioresistance of hypoxic tumors, thus increasing the biological effectiveness relative to low linear energy transfer x-ray or electron beams. Cells irradiated by heavy ions show less variation in cell-cycle-related radiosensitivity and decreased repair of radiation injury. The physical parameters of these heavy charged particles allow precise delivery of high doses to tumors while minimizing irradiation of normal tissues. Clinical use requires a close interaction between radiation oncologists, medical physicists, accelerator physicists, engineers, computer scientists, and radiation biologists.