Abstract
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.
Highlights
Brachytherapy (BT) and external beam radiotherapy (EBRT) apply different dose rates, overall treatment times, energies and fractionation
High dose rate (HDR) brachytherapy is most frequently used in a fractionated manner, in our centre, prostate high dose rate (HDR) BT is given in a single fraction
Hochberg correction of multiple testing we found that 9 months after Low dose rate (LDR) therapy the chromosome aberration values correlated positively and significantly with the largest isodose surface volumes (ISVs), namely V1%, V1Gy
Summary
Brachytherapy (BT) and external beam radiotherapy (EBRT) apply different dose rates, overall treatment times, energies and fractionation. 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. Biologically the BT and EBRT treatments differ substantially[2] They use different overall treatment times and dose rates. We investigated the total effect of the other characteristics of the modalities (photon energy, dose rate, overall treatment time and fractionation). Numerous studies showed that radiotherapy can modify the number, distribution and activity of the different immune cell populations[6]. We obtained data on the distribution of chromosome aberrations in the lymphocyte population, our data might be suitable for testing these models
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