title: Mobilization of viable tumor cells into the circulation during radiation therapy.
abstract: OBJECTIVE
  To determine whether radiation therapy (RT) could mobilize viable tumor cells into the circulation of non-small cell lung cancer (NSCLC) patients.
  
  
  METHODS
  We enumerated circulating tumor cells (CTCs) by fluorescence microscopy of blood samples immunostained with conventional CTC markers. We measured their DNA damage levels using γ-H2AX, a biomarker for radiation-induced DNA double-strand breaks, either by fluorescence-activated cell sorting or by immunofluorescence microscopy.
  
  
  RESULTS
  Twenty-seven RT-treated NSCLC patients had blood samples analyzed by 1 or more methods. We identified increased CTC numbers after commencement of RT in 7 of 9 patients treated with palliative RT, and in 4 of 8 patients treated with curative-intent RT. Circulating tumor cells were also identified, singly and in clumps in large numbers, during RT by cytopathologic examination (in all 5 cases studied). Elevated γ-H2AX signal in post-RT blood samples signified the presence of CTCs derived from irradiated tumors. Blood taken after the commencement of RT contained tumor cells that proliferated extensively in vitro (in all 6 cases studied). Circulating tumor cells formed γ-H2AX foci in response to ex vivo irradiation, providing further evidence of their viability.
  
  
  CONCLUSIONS
  Our findings provide a rationale for the development of strategies to reduce the concentration of viable CTCs by modulating RT fractionation or by coadministering systemic therapies.
authors: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia; Molecular Radiation Biology Laboratory, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia; The Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, VIC, Australia.
authors: Olga A
authors: OA
authors: Martin
authors: The Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, VIC, Australia; Metastasis Research Laboratory, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia.
authors: Robin L
authors: RL
authors: Anderson
authors: Department of Anatomical Pathology, St. Vincent Hospital, Fitzroy, VIC, Australia.
authors: Prudence A
authors: PA
authors: Russell
authors: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia.
authors: R Ashley
authors: RA
authors: Cox
authors: Molecular Radiation Biology Laboratory, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia; Laboratory of DNA Repair and Genomics, Centre for Innate Immunity and Infectious Disease, Monash Institute for Medical Research, Monash University, Clayton, VIC, Australia.
authors: Alesia
authors: A
authors: Ivashkevich
authors: Metastasis Research Laboratory, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia.
authors: Agnieszka
authors: A
authors: Swierczak
authors: Metastasis Research Laboratory, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia.
authors: Judy P
authors: JP
authors: Doherty
authors: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia.
authors: Daphne H M
authors: DH
authors: Jacobs
authors: Molecular Radiation Biology Laboratory, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia.
authors: Jai
authors: J
authors: Smith
authors: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia.
authors: Shankar
authors: S
authors: Siva
authors: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia.
authors: Patricia E
authors: PE
authors: Daly
authors: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia; The Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, VIC, Australia.
authors: David L
authors: DL
authors: Ball
authors: Molecular Radiation Biology Laboratory, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia; The Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, VIC, Australia.
authors: Roger F
authors: RF
authors: Martin
authors: Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia; The Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, VIC, Australia. Electronic address: Michael.macmanus@petermac.org.
authors: Michael P
authors: MP
authors: MacManus
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis; D002289:Carcinoma, Non-Small-Cell Lung / Q000097:blood / Q000473:pathology / Q000532:radiotherapy*; D049109:Cell Proliferation / Q000528:radiation effects; D002470:Cell Survival; D053903:DNA Breaks, Double-Stranded; D006657:Histones / Q000032:analysis*; D006801:Humans; D008175:Lung Neoplasms / Q000097:blood / Q000473:pathology / Q000532:radiotherapy*; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D009360:Neoplastic Cells, Circulating / Q000473:pathology / Q000528:radiation effects*
chemical_list: D014408:Biomarkers, Tumor; C468783:H2AX protein, human; D006657:Histones