Antitumor Effect of Helium Ions with Energy of 320 MeV/Ion during Irradiation of Ehrlich Ascites Carcinoma Cells Ex Vivo.

The regularities of tumor induction and growth were studied in mice after a single ex vivo irradiation with a helium ion beam of Ehrlich adenocarcinoma ascites cells (EAC) at doses of 10 and 20 Gy in two positions of the Bragg curve (before the peak and at the peak) in comparison with X-ray radiation at the same doses. It was shown that the frequency of induction and delay in tumor appearance depend on the dose of helium ion irradiation. The following parameters were determined: the time of a fivefold increase in the EAC volume, tumor growth inhibition, tumor growth index (TGI), and lifetime increase (LTI) in mice. A decrease in the TGI values and an increase in the LTI values occurred with increasing dose for all types of radiation. The relative biological effectiveness (RBE) value for helium ions determined by the area under the EAC growth dynamics curves reached a maximum value of 1.8 upon irradiation at the Bragg peak at a dose of 20 Gy.