Late reactions and complications in patients treated with high energy neutrons p (66MeV) Be(49MeV)

Abstract

Eight of 22 patients who were followed for a year or more after neutron doses in excess of 20 Gy slowed significant late reactions. Late reactions were also observed in 6 of 20 patients who were treated with a neutron boost of 7.5 Gy following 50 Gy of photons for intraoral cancer, and in 5 of 9 ‘mixed beam’ patients who received 9 to 11 neutron Gy with 45 to 50 photon Gy concurrently over a seven week treatment period. Nine of 20 patients who were treated with curative doses of neutrons following recurrence after radical photon therapy had excessively severe late effects. In the neutron only group, a tentative isoeffect line (dose versus fractions) for cutaneous fibrosis could be drawn with an origin at 20 Gy and a slope of 0.04. A time-dose factors analysis of the whole series suggested that a TDF of 120 (±10) defined the threshold for severe stromal fibrosis and associated complications.