Dependence of Cell Survival on Iododeoxyuridine Concentration in 35-keV Photon-Activated Auger Electron Radiotherapy

Journal Article · Sat Jan 01 00:00:00 EST 2011 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2010.07.023· OSTI ID:21499709

Varnes, Marie E ^[1]; Sajo, Erno; Welch, Christopher E ^[1]; Ham, Kyungmin ^[2]; Hogstrom, Kenneth R ^[1]

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1. Department of Physics and Astronomy, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, LA (United States)
2. Center for Advanced Microstructures and Devices, Louisiana State University and Agricultural and Mechanical College, Baton Rouge, LA (United States)

Purpose: To measure and compare Chinese hamster ovary cell survival curves using monochromatic 35-keV photons and 4-MV x-rays as a function of concentration of the radiosensitizer iododeoxyuridine (IUdR). Methods and Materials: IUdR was incorporated into Chinese hamster ovary cell DNA at 16.6 {+-} 1.9%, 12.0 {+-} 1.4%, and 9.2 {+-} 1.3% thymidine replacement. Cells were irradiated from 1 to 8 Gy with 35-keV synchrotron-generated photons and conventional radiotherapy 4-MV x-rays. The effects of the radiation were measured via clonogenic survival assays. Surviving fraction was plotted vs. dose and fit to a linear quadratic model. Sensitization enhancement ratios (SER{sub 10}) were calculated as the ratio of doses required to achieve 10% surviving fraction for cells without and with DNA-incorporated IUdR. Results: At 4 MV, SER{sub 10} values were 2.6 {+-} 0.1, 2.2 {+-} 0.1, and 1.5 {+-} 0.1 for 16.6%, 12.0%, and 9.2% thymidine replacement, respectively. At 35 keV, SER{sub 10} values were 4.1 {+-} 0.2, 3.0 {+-} 0.1, and 2.0 {+-} 0.1, respectively, which yielded SER{sub 10} ratios (35 keV:4 MV) of 1.6 {+-} 0.1, 1.4 {+-} 0.1, and 1.3 {+-} 0.1, respectively. Conclusions: SER{sub 10} increases monotonically with percent thymidine replacement by IUdR for both modalities. As compared to 4-MV x-rays, 35-keV photons produce enhanced SER{sub 10} values whose ratios are linear with percent thymidine replacement and assumed to be due to Auger electrons contributing to enhanced dose to DNA. Although this Auger effectiveness factor is less than the radiosensitization factor of IUdR, both could be important for the clinical efficacy of IUdR radiotherapy.

• OSTI ID: 21499709
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Vol. 79, Issue 1; Other Information: DOI: 10.1016/j.ijrobp.2010.07.023; PII: S0360-3016(10)00954-5; Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BRACHYTHERAPY
CHO CELLS
IODODEOXYURIDINE
MONOCHROMATIC RADIATION
PHOTONS
SURVIVAL CURVES
SYNCHROTRONS
THYMIDINE
ACCELERATORS
ANIMAL CELLS
ANTIMETABOLITES
AZINES
BOSONS
CYCLIC ACCELERATORS
DRUGS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
IODOURACILS
MASSLESS PARTICLES
MEDICINE
NUCLEAR MEDICINE
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC IODINE COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRIMIDINES
RADIATIONS
RADIOLOGY
RADIOTHERAPY
RIBOSIDES
SOMATIC CELLS
THERAPY
URACILS