Relation between chromosomal aberrations and radiation dose during the process of TBI

The purposes of this study were (1) to consider the dose-response relationship in-vivo at high dose range by using the Colcemid method, which begins with predicting the risk of future late complication caused by a fixed dose of chromosomal aberration of peripheral lymphocytes after radiation emission and (2) to compare in-vivo and in-vitro dose-responses for chromosomal aberrations in lymphocytes of cancer patients undergoing total body irradiation (TBI).

Eight patients diagnosed with hematological malignancies entered this study. TBI planning with a 6 MV linear accelerator consisted of 4 Gy/2 fractions/day, and the total treatment dose was 12 Gy.

At the observable dose range of up to 10 Gy, the unstable chromosomal aberrations of both dicentrics and fragments increased with the increment of irradiated dose, regardless of in-vivo or in-vitro irradiated samples. However, the average number of dicentrics and fragments obtained from in-vitro samples was found to be higher than that for in-vivo samples.

This result strongly suggests that in-vivo dose-response curves are necessary to estimate the absorbed dose in-vivo. In-vivo dose-response curves obtained from cancer patients would be very important for standard curves for biodosimetry.