Abstract
Radiotherapy treatment is expected to be applied to intraoral melanoma in a dog, since the surgical treatment accompanies massive degradation of the QOL and mental distress of an owner by a change of the exterior.
Melanoma is resistant to X-ray, so it is expected to apply ion beams, which have Bragg peak and high biological effect, to the radiotherapy.
But, the report about the radiosensitivity of canine spontaneous melanoma is not enough.
We irradiated some of different radiation, carbon ion (LET=108 keV/ μm), proton (LET=2.7 keV/μm) and X-ray (LET=1.0 keV/μm) at TIARA for established cell line (CMM2) of canine spontaneous melanoma origin in this study.
We evaluated the lethal effect in low dose from high dose range by clonogenic assay. After irradiation, the cells were plated at a moderate density. 8 days later, the cells were fixed and stained. We made survival curves from the results.
While survival curves for the cell line after X-ray and proton irradiation had a shoulder in low dose, survival curve for the cell line after carbon ion irradiation didn't have a shoulder, and the surviving fraction in low dose was much lower than the extrapolated survival curve.
When we compared the lethal effect at D10 to estimate the difference between radiation, lethal effect of cell was high in order of carbon ion, proton, X-ray, and it was observed that RBE based on X-ray was increasing with LET.
This result indicates that the lethal effect of cell increase with LET, and it was thought that application of carbon ion to an intraoral melanoma was effective on the therapy.
