One significant finding… was that only neutron beams produced by protons or deuterons with energies greater than about 50 MeV could produce tumor control with side effects no worse than low LET radiation.

Sir James Chadwick discovered neutrons in 1932. Just six years later, Dr. Robert Stone began clinical trials treating cancer with neutrons produced by E.O. Lawrence's cyclotron in Berkeley, California. These trials were terminated because the cyclotron was needed for the war effort during World War II. Clinical research began again in 1965 when Dr. Mary Catterall at Hammersmith Hospital in London began irradiating patients with neutron beams. By 1969, it was clear that for certain tumors, better local control could be achieved using neutron irradiation. Encouraged by these results, the M.D. Anderson Hospital and Tumor Institute in Houston, the Naval Research Laboratory in Washington, D.C., and the University of Washington in Seattle began neutron therapy research. They started treating patients in the early 1970s.

During the mid-1970s Chicago-area radiation oncologists, Lionel Cohen, M.D. and Frank Hendrickson, M.D., worked with Dr. Robert R. Wilson (Fermilab Director from 1968 until July 1978) to build the Neutron Therapy Facility (NTF) at Fermilab. Measurements of neutron beam characteristics and dose distributions were completed in 1976; patient treatments were begun September 7, 1976. The National Cancer Institute funded the operation of the facility from June 30, 1975, until October 1, 1985. During that period NTF conducted clinical trials to determine the appropriateness of using neutrons to treat various types of cancers. Initial research included using different doses in order to determine the optimum, safe theraputic dose with minimum treatment-related late side effects. Some of the trials involved randomly assigning eligible patients to receive either the best conventional treatment for their cancer, or neutrons, which at the time were considered to be experimental. This was done only with the patient's permission. Fermilab's treatment results using a high energy neutron beam were combined and analyzed with the results from other facilities.

One significant finding which came out of these multi-institutional trials was that only neutron beams produced by protons or deuterons with energies greater than about 50 MeV could produce tumor control with side effects no worse than low LET radiation. For this reason facilities which had performed clinical trials using relatively low energy beams either stopped treating patients or upgraded their accelerators to a higher energy.