Fast neutron therapy clinical trials in the United States.

The National Cancer Institute (NCI) began supporting clinical fast neutron clinical studies in the United States beginning in the early 1970s using physics-based cyclotrons and linear accelerators at a number of locations and facilities. The early work pointed out the handicaps imposed by the limitations of horizontal beams and low energy neutrons. This, combined with some encouraging, clinical results using neutrons and photons in a mixed mode of therapy, prompted the NCI in 1979 to initiate a 10-year contract program to design, develop, and build hospital-based neutron therapy machines and to conduct phase III clinical trials. As we approach the end of the 10-year effort, three hospital-based neutron facilities are currently operational-at the University of Washington, Seattle; University of California at Los Angeles: and M. D. Anderson Hospital at University of Texas System Cancer Center, Houston. Phase III trials are in progress in four sites: head and neck, prostate, and lung tumors, and cancers of radioresistant histologies, such as melanoma, renal cell carcinoma, and sarcomas of the soft tissue and bone. The contractors will continue to receive limited NCI support to complete the clinical studies.