Pions, Vancouver.

Clinical treatments at TRIUMF started in November, 1979. Ten patients with malignant subcutaneous nodules had 14 lesions treated with pions and 37 other nodules treated with 280 kV X rays. Three different fractionation regimens were used with X ray doses spanning the expected RBE range of pions. The RBE for pions for acute skin reaction for 10 fractions had a mean value about 1.5, while for 3 fractions it was 1.3 maximum. No dissociation of acute and late skin effects was seen with follow-up to 27 months after treatment. Phase 1-2 studies of Pion-Boost Therapy for patients with glioblastoma multiforme will begin in May, 1982. These will be followed in August with treatments of advanced pelvic malignancies using pions only. The existing beam line at TRIUMF will be upgraded and commitments have been given to go to higher beam currents. As a result, the dose rate should increase by a factor of at least two, allowing treatment of clinically relevant volumes in acceptable times by 1983-1984.