Effects of the alpha-particle emitter At-211 and low-dose-rate gamma-radiation on the human cell line Colo-205 as studied with a growth assay

• BACKGROUND: The aim of this study was to investigate the biological effect of the alpha-particle-emitting isotope astatine-211 on the human cell line Colo-205 and to compare it with that of low-dose-rate gamma-radiation. MATERIALS AND METHODS: Plastic (PMMA) rotating phantoms were constructed, allowing precise dosimetry on a cellular level for both types of radiation. Growth assays using 96-well plates were used to estimate apparent cell survival for the two types of radiation. From this, the relative biological effect (RBE) could be estimated. RESULTS: Irradiation of the cells with 211At resulted in an RBE of 25.1 +/- 6.7 at 37% survival, and 17.3 +/- 2.5 at 10% survival, when compared with low-dose-rate gamma-irradiation. The absorbed dose at 37% survival, 0.12 Gy, corresponds to 2.2 traversals of alpha-particles through the cell nuclei. For cells irradiated with gamma-radiation (1 and 2 Gy), an apparent cell survival above unity was observed up to 50 hours post-irradiation, indicating a possible radiation hormesis effect. CONCLUSIONS: The RBE of 211At found in this growth-assay study was significantly higher than previously presented values. The difference might be due to the use of low-dose-rate gamma-radiation as reference. The RBE presented here could prove valuable when evaluating 211At-labelled compounds for radiotherapy.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Cancer och onkologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Cancer and Oncology (hsv//eng)

Nyckelord

*Alpha Particles

*Astatine

Cell Division/*radiation effects

Cell Survival/*radiation effects

Colonic Neoplasms

Gamma Rays

Humans

Phantoms

Imaging

Polymethyl Methacrylate

Time Factors

Tumor Cells

Cultured

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