Enhanced Neoplastic Transformation by Mammography X Rays Relative to 200 kVp X Rays: Indication for a Strong Dependence on Photon Energy of the RBE_Mfor Various End Points

Abstract

The fundamental assumption implicit in the use of the atomic bomb survivor data to derive risk estimates is that the gamma rays of Hiroshima and Nagasaki are considered to have biological efficiencies equal to those of other low-LET radiations up to 10 keV/microm, including mammography X rays. Microdosimetric and radiobiological data contradict this assumption. It is therefore of scientific and public interest to evaluate the efficiency of mammography X rays (25-30 kVp) to induce cancer. In this study, the efficiency of mammography X rays relative to 200 kVp X rays to induce neoplastic cell transformation was evaluated using cells of a human hybrid cell line (CGL1). For both radiations, a linear-quadratic dose-effect relationship was observed for neoplastic transformation of CGL1 cells; there was a strong linear component for the 29 kVp X rays. The RBE(M) of mammography X rays relative to 200 kVp X rays was determined to be about 4 for doses < or = 0.5 Gy. A comparison of the electron fluences for both X rays provides strong evidence that electrons with energies of < or = 15 keV can induce neoplastic transformation of CGL1 cells. Both the data available in the literature and the results of the present study strongly suggest an increase of RBE(M) for carcinogenesis in animals, neoplastic cell transformation, and clastogenic effects with decreasing photon energy or increasing LET to an RBE(M) approximately 8 for mammography X rays relative to 60Co gamma rays.

p53 Ser15 phosphorylation and histone modifications contribute to IR-induced miR-34a transcription in mammary epithelial cells

“…Having seen oncotransformation potential than the 200 kVp X-rays, suggesting that the low-energy X-rays used in mammography are considerably more biologically active than previously thought. [9][10][11] This finding is consistent with data on chromosome aberration induction by low-energy X-rays. 12 Furthermore, it is now well-accepted that even low doses of IR can cause oxidatively generated clustered DNA lesions.…”

A randomised trial of Supine versus Prone breast radiotherapy (SuPr study): Comparing set-up errors and respiratory motion

“…Another means by which prone treatment could become a viable standard treatment option is to optimize verification. CBCT as used here and in NYUH is one possibility but, given the potential long-term risks of exposure to low-dose ionizing radiation (20,21), may not be justifiable in the context of patients with low-risk disease, especially given that the basis for pursuing prone treatment is reduction of long-term side-effects. Other technologies that can be used to localize soft tissue targets include implanted transponder systems, implantable dosimeters, and opto-electronic surface imaging (22)(23)(24).…”

Induction of micronuclei in human fibroblasts and keratinocytes by 25 kV x-rays

“…During recent years there have been several reports about an enhanced risk from exposure to soft x-rays (up to -50 kV) compared to conventional x-rays or ?-rays [ 1,2]. It has been shown that soft x-rays can be more effective in cell killing [3,4,5,6], induction of chromosome aberrations [7,8,9] and neoplastic transformations [6]. Virsik et al [7] found higher yields of dicentric chromosomes in human lymphocytes for 30 kV x-rays compared to 150 kV x-rays resulting in RBE values of 1.25 up to 3 for high and low doses, respectively.…”