title: Complex aberrations in lymphocytes exposed to mixed beams of (241)Am alpha particles and X-rays.
abstract: Modern radiotherapy treatment modalities are associated with undesired out-of-field exposure to complex mixed beams of high and low energy transfer (LET) radiation that can give rise to secondary cancers. The biological effectiveness of mixed beams is not known. The aim of the investigation was the analysis of chromosomal damage in human peripheral blood lymphocytes (PBL) exposed to a mixed beam of X-rays and alpha particles. Using a dedicated exposure facility PBL were exposed to increasing doses of alpha particles (from (241)Am), X-rays and a mixture of both. Chromosomal aberrations were analysed in chromosomes 2, 8 and 14 using fluorescence in situ hybridisation. The found and expected frequencies of simple and complex aberrations were compared. Simple aberrations showed linear dose-response relationships with doses. A higher than expected frequency of simple aberrations was only observed after the highest mixed beam dose. A linear-quadratic dose response curve for complex aberrations was observed after mixed-beam exposure. Higher than expected frequencies of complex aberrations were observed for the two highest doses. Both the linear-quadratic dose-response relationship and the calculation of expected frequencies show that exposure of PBL to mixed beams of high and low LET radiation leads to a higher than expected frequency of complex-type aberrations. Because chromosomal changes are associated with cancer induction this result may imply that the cancer risk of exposure to mixed beams in radiation oncology may be higher than expected based on the additive action of the individual dose components.
authors.affiliation: Centre for Radiation Protection Research, MBW Department, Stockholm University, Sweden.
authors.forename: Elina
authors.initials: E
authors.lastname: Staaf
authors.forename: Marta
authors.initials: M
authors.lastname: Deperas-Kaminska
authors.forename: Karl
authors.initials: K
authors.lastname: Brehwens
authors.forename: Siamak
authors.initials: S
authors.lastname: Haghdoost
authors.forename: Joanna
authors.initials: J
authors.lastname: Czub
authors.forename: Andrzej
authors.initials: A
authors.lastname: Wojcik
mesh_terms: D000328:Adult; D000512:Alpha Particles; D000576:Americium; D002478:Cells, Cultured; D002842:Chromatids / Q000235:genetics / Q000528:radiation effects*; D002869:Chromosome Aberrations / Q000528:radiation effects*; D004249:DNA Damage / Q000235:genetics / Q000528:radiation effects; D004260:DNA Repair / Q000235:genetics / Q000528:radiation effects; D006801:Humans; D007091:Image Processing, Computer-Assisted; D017404:In Situ Hybridization, Fluorescence; D018499:Linear Energy Transfer; D008214:Lymphocytes / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D008297:Male; D014965:X-Rays
chemical_list: D000576:Americium
keywords: Aberrations; High LET; Low LET; Mixed beams; Radiotherapy