Analysis of 177Lu-DOTA-octreotate therapy-induced DNA damage in peripheral blood lymphocytes of patients with neuroendocrine tumors.
Ionizing radiation-induced DNA double-strand breaks (DSBs) can lead to cell death, genome instability, and carcinogenesis. Immunofluorescence detection of phosphorylated histone variant H2AX (γ-H2AX) is a reliable and sensitive technique to monitor external-beam ionizing radiation-induced DSBs in peripheral blood lymphocytes (PBLs). Here, we investigated whether γ-H2AX could be used as an in vivo marker to assess normal-tissue toxicity after extended internal irradiation with (177)Lu-DOTA-octreotate (LuTate) peptide receptor radionuclide therapy (PRRT) of neuroendocrine tumors.


METHODS
We analyzed the kinetics of γ-H2AX foci in PBLs of 11 patients undergoing PRRT. The number of γ-H2AX foci was determined before and up to 72 h after treatment. These values were compared with the estimated absorbed dose to blood, spleen, bone marrow, and tumor and with subsequent PBL reduction.


RESULTS
The decrease in (177)Lu activity in blood with time followed a biexponential kinetic pattern, with approximately 90% of circulating activity in blood cleared within 2 h. Absorbed dose to blood, but not to spleen or bone marrow, correlated with the administered (177)Lu activity. PRRT increased γ-H2AX foci in lymphocytes in all patients, relative to pretherapy values. The response varied significantly between patients, but the average number of foci indicated a general trend toward an increase at 0.5-4 h with a subsequent decrease by 24-72 h after treatment. The peak number of foci correlated with the absorbed dose to tumor and bone marrow and the extent of PBL reduction.


CONCLUSIONS
γ-H2AX can be exploited in the LuTate PRRT as a biomarker of PBL cytotoxicity. Long-term follow-up studies investigating whether elevated residual γ-H2AX values are associated with acute myelotoxicity and secondary blood malignancy may be worthwhile.
Molecular Imaging and Targeted Therapeutics, Translational Research Laboratory, Peter MacCallum Cancer Centre, Melbourne, Australia Centre for Cellular and Molecular Biology, Deakin University, Burwood, Australia olga.martin@petermac.org d.denoyer@deakin.edu.au.
Delphine
D
Denoyer
Molecular Radiation Biology Laboratory, Peter MacCallum Cancer Centre, Melbourne, Australia Sir Peter MacCallum Department of Oncology, University of Melbourne, Australia; and.
Pavel
P
Lobachevsky
Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Australia.
Price
P
Jackson
Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Australia.
Mick
M
Thompson
Molecular Radiation Biology Laboratory, Peter MacCallum Cancer Centre, Melbourne, Australia Sir Peter MacCallum Department of Oncology, University of Melbourne, Australia; and Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Australia. olga.martin@petermac.org d.denoyer@deakin.edu.au.
Olga A
OA
Martin
Molecular Imaging and Targeted Therapeutics, Translational Research Laboratory, Peter MacCallum Cancer Centre, Melbourne, Australia Sir Peter MacCallum Department of Oncology, University of Melbourne, Australia; and Division of Radiation Oncology and Cancer Imaging, Peter MacCallum Cancer Centre, Melbourne, Australia.
Rodney J
RJ
Hicks
D000328:Adult; D000368:Aged; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D005260:Female; D006657:Histones / Q000737:chemistry*; D006801:Humans; D007700:Kinetics; D008214:Lymphocytes / Q000528:radiation effects*; D008297:Male; D008856:Microscopy, Fluorescence; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000378:metabolism / Q000628:therapy*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000627:therapeutic use; D009942:Organometallic Compounds / Q000627:therapeutic use*; D010766:Phosphorylation; D011874:Radiometry; D018000:Receptors, Peptide / Q000378:metabolism; D013997:Time Factors
C554548:177Lu-octreotate; C468783:H2AX protein, human; D006657:Histones; D009942:Organometallic Compounds; D018000:Receptors, Peptide; C447941:lutetium Lu 177 dotatate; D015282:Octreotide
177Lu-octreotate; DNA damage; PRRT; normal tissue toxicity; γ-H2AX