Biological effects of hepatoma cells irradiated by 25MeV/u(40)Ar(14+).

Abstract

Radiotherapy was initiated when Grubbe treated tumor with X-rays in 1896[1]. Afterwards, radioisotopes such as Ra and Rn, were used for clinical diagnosis and treatment. Basic researches on the biological effects of X-rays, γ-rays, fast neutron, and so on discovered that damages to mammalian cells induced by high-LET irradiation were more serious than that by low-LET[2]. Because of their low oxygen enhancement ratio (OER) and high relative biological effectiveness (RBE), heavy ions can kill carcinoma cells efficiently[3], among which about 5%-20% was hypoxia. There was a Bragg peak along the energy deposition of heavy ions, so that more dose could reach to the tumor while less to the normal tissues[4]. Therefore, heavy ion beam is believed to play an important role in the future in the radiotherapy for tumors. The treatment with heavy ion beam has been studied and put into clinical practice since the 1970s in America and since 1994 in Japan. But in our country, this research is still in its initial stage. This is our preliminary report on the dose--response and fractionated irradiation with 25MeV/u 40Ar14+ in human hepatoma SMMC-7721 cells.