Biodosimetric assessment of micronuclei in lymphocytes of patients with pelvic radiotherapy

Abstract

To further verify the applicability of the micronuclei (MN) assay for clinical biodosimetry, we measured the MN yield in cytokinesis-blocked (CB) peripheral blood lymphocytes (PBL) of 12 patients with primary cancers of either prostate (n=9) or testis (n=3). These patients had no previous chemotherapy or radiotherapy (xRT). They were treated with standardized schemes of fractionated pelvic xRT. Before xRT, and at 1-3 random time-point during the course of xRT, blood samples were collected from each patient for the following purposes: (1) to assess the impact of pelvic xRT on the MN yield; and (2) to verify the relationship between the MN yield and the estimated equivalent (EQ) total-body absorbed dose. The number of xRT fractions,cumulative tumor doses, and EQ total-body absorbed doses of these patients represented in a wide range. We found that (1) before xRT, the mean(SD) yield of MN baseline level was 13.6 (6.9) per 1000 binucleated PBL. However, during the course of xRT (3-37 fractions), it increased to 84.3 (59.3). The ratio of relative increment of MN yield ranged from 0.9-17.0 folds above that of the respective baseline levels in each patient; and (2) MN yield (Y) increased with the estimated EQ dose (D) as Y=7.8+13.6D (r=0.8, p=0.0001). The distributions of MN yield were overdispersed in 11 patients, relative to dispersion expected under a Poisson model. Our findings indicate that the MN yield in CB PBL of cancer patients offers a reliable biodosimeter for EQ total-body absorbed radiation dose estimation.