Mouse skin reactions following fractionated irradiation with carbon ions.

PURPOSE

Skin reactions in the mouse leg following various daily doses given with 290 MeV/u carbon ions were investigated.

MATERIALS AND METHODS

Seven different LET (linear energy transfer) values ranging from 14 to 100keV/microm were selected. The fractionation schedules were 1-, 2-, 4- and 8-daily fractions. The isoeffect doses to produce moist desquamation on the dose-response curves were calculated with 95% confidence limits.

RESULTS

The isoeffect doses for carbon ions of 14 and 20 keV/microm increased with an increase in the number of fractions up to 4 fractions, but became constant when the number of fractions further increased to 8 fractions. This leveling off in isoeffect dose was more prominent for 40 keV/microm. Recovered dose per fraction was largest for 2 fractions of the 14keV/microm carbon beam. The isoeffect doses for 50, 60, 80 and 100keV/microm consistently increased with an increase in the number of fractions and did not show saturation up to 8 fractions. RBE (relative biological effectiveness) increased linearly with LET for all fractionation schedules.

CONCLUSIONS

These results suggest that daily fractionation with carbon ions could spare radiation damage in patients, and that changes the fractionation schedule affect clinical outcome.