Correlation of Decline in Platelet Count and Radiation Induced Foci of Blood Lymphocytes for Patients Undergoing Lu-177 Radioligand Therapy

Ziel/Aim DNA double-strand breaks in blood lymphocytes of Lu-177-treated patients can be quantified by immunofluorescence microscopy, using phosphorylation of histone variant H2AX (γ-H2AX) to mark radiation-induced foci (RIF). RIF are presumed to positively correlate with increased DNA damage, potential DNA disrepair, and functionally impaired cells. Furthermore, ionizing radiation is a well-known cause of dose-dependent deteriorations in all hematopoietic cell lines. The time course after exposure depends on cell type. Thrombocytes/platelets decline within days after exposure.

The aim of this study was to determine if suspected correlation between the number of RIF and decline in platelet count exists. This potentially could be used for controlling hematopoietic system normal tissue complication probability (NTCP) of Lu-177 therapy.

Methodik/Methods Venous blood samples were obtained from 48 patients subjected to Lu-177-labeled radioligand therapy (DOTATOC, 26; PSMA, 22) to quantify blood lymphocyte RIF at various time points, including baseline (prior to injection) and post injection (PI) readings (5 min, 30 min, 4 h, 24 h, 48 h, and 72 h). Platelet levels in routine blood tests were monitored for 3 days PI to assess responses.

Ergebnisse/Results Change in thrombocyte count (%), significantly correlated with average RIF count per cell at 72 h PI for all 48 patients (Pearson’s r=-0.34; p < 0.05).

The corresponding linear fit yielded an R² of 0.11 and resulted in the following equation:

% Change in thrombocyte count = (-4.3 ± 2.7) - (9.9 ± 4.9) · RIF

Schlussfolgerungen/Conclusions The results suggest that radiation-induced damage to the DNA parallels damages to cellular systems such as hematopoiesis. Our data suggest that determining RIF may help estimating NTCP.

Publication History

Article published online:
08 April 2021