The edinburgh experience of fast neutron therapy

Abstract

The Edinburgh experience is based on a d(15 + Be neutron beam generated by a compact CS 30 Cyclotron. The facility has an iso-center treatment head providing 240° of rotation. The most important limitation of the beam is its poor penetrating quality. We have compared neutron therapy alone given in 20 daily fractions over four weeks with photon therapy given in the same fractionation schedule. Since clinical studies began in March, 1977, over 500 patients have been treated by fast neutrons. Almost all patients are now admitted to randomly controlled trials. In the head and neck trial conducted in collaboration with colleagues in Amsterdam and Essen,192 patients are available for analysis. Most patients had T3 lesions and about 50% had involved nodes. The cumulative regression rate at six months is similar after neutrons and photons (75%). Later recurrence rates (36%) are also similar. The early radiation morbidity is similar in both groups, but the late reactions are greater after neutrons (15%) than photons (6%). Overall survival is better after photon therapy. A trial of patients with glioblastoma has also shown a better survival after photon therapy. Neutron therapy was associated with demelinization in three of 18 patients. Patients with transitional cell cancer of the bladder have also been the subject of study. Local tumor control was similar (53%) after neutrons and photons. Late radiation morbidity was much greater after neutrons (20%), compared with photons (2%). In a trial of advanced carcinoma of the rectum, the local tumor control was also similar after neutrons and photons (30%), but morbidity was greater after neutrons. Soft tissue sarcomas have shown response rates (37%) that may be expected after photon therapy. Salivary gland tumors have shown a similar experience, although slow growing tumors such as adenoid cystic carcinoma may respond better to neutrons. The response of malignant melanoma also requires further evaluation. No qualitative advantage of neutrons in relation to tumor responses has been determined, while increased late radiation morbidity has been demonstrated following the dose-time schedules used.