Neoplastic transformation induced by carbon ions.
OBJECTIVE
The objective of this experiment was to compare the oncogenic potential of carbon ion beams and conventional photon beams for use in radiotherapy.


METHODS
The HeLa X human skin fibroblast cell line CGL1 was irradiated with carbon ions of three different energies (270, 100, and 11.4 MeV/u). Inactivation and transformation data were compared with those for 15 MeV photons.


RESULTS
Inactivation and transformation frequencies for the 270 MeV/u carbon ions were similar to those for 15-MeV photons. The maximal relative biologic effectiveness (RBE(alpha)) values for 100MeV/u and 11.4 MeV/u carbon ions, respectively, were as follows: inactivation, 1.6 +/- 0.2 and 6.7 +/- 0.7; and transformation per surviving cell, 2.5 +/- 0.6 and 12 +/- 3. The curve for dose-transformation per cell at risk exhibited a maximum that was shifted toward lower doses at lower energies.


CONCLUSIONS
Transformation induction per cell at risk for carbon ions in the entrance channel was comparable to that for photons, whereas for the lower energies, 100 MeV/u and 11 MeV/u, which are representative of the energies delivered to the tumor margins and volume, respectively, the probability of transformation in a single cell was greater than it was for photons. In addition, at isoeffective doses with respect to cell killing, the 11.4-MeV/u beam was more oncogenic than were photons.
Bettega
Daniela
D
Dipartimento di Fisica, Università di Milano and Istituto Nazionale di Fisica Nucleare, Milano, Italy. Bettega@mi.infn.it
Calzolari
Paola
P
Hessel
Petra
P
Stucchi
Claudio G
CG
Weyrather
Wilma K
WK
D002244:Carbon / Q000009:adverse effects; D002250:Carbon Radioisotopes / Q000009:adverse effects*; D002467:Cell Nucleus / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D004249:DNA Damage; D005347:Fibroblasts / Q000473:pathology / Q000528:radiation effects; D006367:HeLa Cells / Q000473:pathology / Q000528:radiation effects; D006801:Humans; D006822:Hybrid Cells / Q000473:pathology / Q000528:radiation effects; D018499:Linear Energy Transfer; D017785:Photons; D016012:Poisson Distribution; D012062:Relative Biological Effectiveness
D002250:Carbon Radioisotopes; D002244:Carbon