DNA damage in blood leucocytes of prostate cancer patients during therapy with 177Lu-PSMA

Abstract

Purpose The aim of this study was to investigate the time- and dose-dependency of DNA double-strand break (DSB) induction and repair in peripheral blood leucocytes of prostate cancer patients during therapy with 177 Lu-PSMA. Methods Blood samples from 16 prostate cancer patients receiving their first 177 Lu-PSMA therapy were taken before and at seven time-points (between 1 h and 96 h) after radionuclide administration. Absorbed doses to the blood were calculated using integrated time–activity curves of the blood and the whole-body. For DSB quantification, leucocytes were isolated, fixed in ethanol and immunostained with γ-H2AX and 53BP1 antibodies. Colocalizing foci of both DSB markers were manually counted in a fluorescence microscope. Results The average number of radiation-induced foci (RIF) per cell increased within the first 4 h after administration, followed by a decrease indicating DNA repair. The number of RIF during the first 2.6 h correlated linearly with the absorbed dose to the blood ( R 2 = 0.58), in good agreement with previously published in-vitro data. At late time-points (48 h and 96 h after administration), the number of RIF correlated linearly with the absorbed dose rate ( R 2 = 0.56). In most patients, DNA DSBs were repaired effectively. However, in some patients RIF did not disappear completely even 96 h after administration. Conclusion The general pattern of the time- and dose-dependent induction and disappearance of RIF during 177 Lu-PSMA therapy is similar to that of other radionuclide therapies.

DNA Damage in Blood Leukocytes of Prostate Cancer Patients Undergoing PET/CT Examinations with [68Ga]Ga-PSMA I&T

“…The average number of RIF per cell in this very low-dose range was higher than expected according to a previously established ex vivo calibration curve for the internal irradiation of blood with the radionuclides 131 I and 177 Lu [10]. The slope of the latter ex vivo calibration curve was (0.0147 ± 0.0006) mGy −1 [10], similar to the slopes of in vivo calibration curves established in several patient studies investigating DSB induction during therapy with 131 I (slope of (0.0117 ± 0.0006) mGy −1 ) [8], [ 177 Lu]Lu-DOTATATE/DOTATOC (slope of (0.0127 ± 0.0009) mGy −1 ) [9] and [ 177 Lu]Lu-PSMA I&T (slope of (0.0122 ± 0.0015) mGy −1 ) [7]. However, all our previous studies [7][8][9][10] mainly covered the dose range between 6 mGy and 100 mGy.…”

“…The slope of the latter ex vivo calibration curve was (0.0147 ± 0.0006) mGy −1 [10], similar to the slopes of in vivo calibration curves established in several patient studies investigating DSB induction during therapy with 131 I (slope of (0.0117 ± 0.0006) mGy −1 ) [8], [ 177 Lu]Lu-DOTATATE/DOTATOC (slope of (0.0127 ± 0.0009) mGy −1 ) [9] and [ 177 Lu]Lu-PSMA I&T (slope of (0.0122 ± 0.0015) mGy −1 ) [7]. However, all our previous studies [7][8][9][10] mainly covered the dose range between 6 mGy and 100 mGy. Compared to these results, the slope in the present study of (0.130 ± 0.018) mGy −1 was approximately ten-fold higher, indicating that DSB induction might be increased in the very low-dose range <10 mGy, indicative of low-dose radio hypersensitivity.…”

“…The additional number of DSB foci induced by CT, however, was comparable to the one induced by 68 Ga. The significantly increased foci numbers after [ 68 Ga]Ga-PSMA administration may suggest a possible low-dose hypersensitivity.Cancers 2020, 12, 388 2 of 14 and 53BP1 DNA DSB damage markers [4][5][6] and the analysis of co-localized γ-H2AX+53BP1 foci in the cell nuclei of peripheral blood leukocytes of prostate cancer patients to assess DSB damage [7]. The time-dependency of the DSB induction is characterized by a linear increase of the number of DSB foci in the first few hours after administration of the radiopharmaceutical, followed by a phase of equilibrium between repair and induction of DSBs, and subsequently by predominant repair leading, in most patients, to a complete decline to baseline foci levels [7][8][9].…”

“…The significantly increased foci numbers after [ 68 Ga]Ga-PSMA administration may suggest a possible low-dose hypersensitivity.Cancers 2020, 12, 388 2 of 14 and 53BP1 DNA DSB damage markers [4][5][6] and the analysis of co-localized γ-H2AX+53BP1 foci in the cell nuclei of peripheral blood leukocytes of prostate cancer patients to assess DSB damage [7]. The time-dependency of the DSB induction is characterized by a linear increase of the number of DSB foci in the first few hours after administration of the radiopharmaceutical, followed by a phase of equilibrium between repair and induction of DSBs, and subsequently by predominant repair leading, in most patients, to a complete decline to baseline foci levels [7][8][9]. Our group applied this DSB damage assay successfully in a number of ex vivo and in vivo studies with different therapeutic radionuclides such as 131 I, 177 Lu and the radium isotopes 223 Ra and 224 Ra [7][8][9][10][11][12][13].Up to now, there are few studies on the formation of DNA DSB damage after the diagnostic application of radiopharmaceuticals.…”

“…The time-dependency of the DSB induction is characterized by a linear increase of the number of DSB foci in the first few hours after administration of the radiopharmaceutical, followed by a phase of equilibrium between repair and induction of DSBs, and subsequently by predominant repair leading, in most patients, to a complete decline to baseline foci levels [7][8][9]. Our group applied this DSB damage assay successfully in a number of ex vivo and in vivo studies with different therapeutic radionuclides such as 131 I, 177 Lu and the radium isotopes 223 Ra and 224 Ra [7][8][9][10][11][12][13].Up to now, there are few studies on the formation of DNA DSB damage after the diagnostic application of radiopharmaceuticals. However, the relationship between damage induction and the absorbed dose has not been investigated so far, making the results of these studies difficult to compare.…”