Biological characteristics of carbon-ion therapy.
OBJECTIVE
Radiotherapy using charged and/or high-linear energy transfer (LET) particles has a long history, starting with proton beams up to now carbon-ions. Radiation quality of particle beams is different from conventional photons, and therefore the biological effects of high-LET irradiation have attracted scientific interests of many scientists in basic and clinical fields. A brief history of particle radiotherapy in the past half-century is followed by the reviewed biological effectiveness of high-LET charged particles.


RESULTS
The latter includes 54 papers presenting 506 RBE (relative biological effectiveness) values for carbon ions and a total of 290 RBE values for other ions identified from 48 papers. By setting a selection window of LET up to 100 keV/microm, we fitted a linear regression line to an LET-RBE relation. The resulting slope of the regression line had a dimension of microm/keV, and showed different steepness for different cells/tissues and endpoints as well. The steepest regression was found for chromosome aberration of human malignant melanoma while the shallowest was for apoptosis of rodent cells/tissue. Both tumour and normal tissue showed relatively shallower slopes than colony formation.


CONCLUSIONS
In general, there is a large variation of slope values, but the majority (25 out of 29 values) of data was smaller than 0.05 microm/keV.
Ando
Koichi
K
Medicine and Biology Division, Gunma University Heavy Ion Medical Center, Showa-machi 3-39-22, Maebashi-shi, Gunma, Japan. kando3@showa.gunma-u.ac.jp
Kase
Yuki
Y
D000818:Animals; D002244:Carbon / Q000737:chemistry* / Q000627:therapeutic use*; D006801:Humans; D018499:Linear Energy Transfer; D011878:Radiotherapy / Q000379:methods*; D012062:Relative Biological Effectiveness
D002244:Carbon