Assessment of acute and late effects to high-LET radiation

We have begun to reassess late tissue effects available from the Charged Particle Cancer Radiotherapy program at Berkeley. Our quantitative approach is limited in the analysis of these Phase I/II studies by not having equivalent patient numbers for each of the particle beams studied, by not having completely comparable follow-up times, by variations in the sizes of the fields compared, by variations in the skin scoring photographic documentation available from the patient charts, and by variations in the fractionation sizes, numbers and schedules. Despite these limitations, preliminary evidence demonstrates acute skin reactions with a shift to increasing lower dose per fraction per field for the maximum skin reactions of helium, carbon and neon ions compared to electrons. Comparisons with skin reactions from low-energy neutrons indicate that Bragg peak carbon ions (initial energy 308 MeV/nucleon) are slightly less effective than 7.5 MeV neutrons. Bragg peak neon ions (initial energy 670 MeV/nucleon) corrected for differences in reference radiation are slightly more effective than 7.5 MeV neutrons. Bragg peak silicon (initial energy 670 MeV/nucleon) result in an enhanced acute skin reaction, and a premature appearance of late effects that may indicate a significantly different mechanism of damage and/or repair