Brachytherapy (BT) and external beam radiotherapy (EBRT) apply different dose rates,
overall treatment times, energies and fractionation. However, the overall impact of
these variables on the biological dose of blood is neglected. As the size of the irradiated
volume influences the biological effect as well, we studied chromosome aberrations
(CAs) as biodosimetric parameters, and explored the relationship of isodose surface
volumes (ISVs: V1%, V1Gy, V10%, V10Gy, V100%, V150%) and CAs of both irradiation modalities.
We performed extended dicentrics assay of lymphocytes from 102 prostate radiotherapy
patients three-monthly for a year. Aberration frequency was the highest after EBRT
treatment. It increased after the therapy and did not decrease significantly during
the first follow-up year. We showed that various types of CAs 9 months after LDR BT,
3 months after HDR BT and in a long time-range (even up to 1 year) after EBRT positively
correlated with ISVs. Regression analysis confirmed these relationships in the case
of HDR BT and EBRT. The observed differences in the time points and aberration types
are discussed. The ISVs irradiated by EBRT showed stronger correlation and regression
relationships with CAs than the ISVs of brachytherapy.
