Fast neutrons irradiation as a way to overcome feline squamous cell carcinoma radioresistance: a pilot study

For the study 4 cats with unresectable oral squamous cell carcinoma were treated with combination of neutron and electron radiations. 3 cats had T2b and one had T3b stage. The first phase of treatment was performed with 14 MeV fast neutron beam, fraction dose varied from 1.0 to 1.3 Gy, 3 fractions a week, 3-5 fractions in total; in the second phase the animals were irradiated with 10 MeV electron beam, using same fractionation, fraction dose varied from 4 Gy, up to total dose of 8-36 Gy. In the course of treatment, most cats had partial or complete anorexia, the duration of which did not exceed two days, it was well controlled by antidepressants (mirtazapinum). Visual assessment and computed tomography performed from 13 to 30 days after treatment completion demonstrated showed the significant regression of tumor volume (30-67%) in all cases. 3 out of 4 animals were alive at the time of the study, average follow-up period was 84 days, maximum follow-up period was 160 days. Radiation damage was limited to local alopecia followed by leukotrichia.