More recently, radiation sensitizing agents that have an effect similar to oxygen have been developed. Other compounds now being investigated are "radioprotectors" that may decrease damage to normal tissues.
High Linear Energy Transfer (LET) Radiation Radiation with accelerators that use heavy particles or subatomic particles rather than electrons, x-rays or gamma rays is now being studied in many centers. Several types of heavy particles are under investigation, including protons, helium ions and neutrons. Two features seem to make this type of radiation—called High Linear Energy Transfer (LET) heavy particle radiation—more effective. First, it can kill poorly oxygenated cells better than standard radiation can. Second, tumor cells are less able to repair sublethal damage from high LET radiation.
Several tumors have been identified that may benefit from high LET particle radiation—including sarcomas of bone and soft tissue, salivary gland tumors, some head and neck tumors and melanomas of the eye—and the search is on to find others. In the past few years, high LET radiation has been used with patients with advanced malignant disease. But it is still an investigational treatment and is available only in a few facilities in the
United States.
Hyperfractionation In recent years there has been considerable interest in hyperfraction, in which patients are given radiation treatment twice daily rather than the conventional once daily. By using multiple smaller doses of radiation, a higher overall dose can be delivered. The treatments are usually given at least 6 hours apart to allow
