Reciprocal translocations in patients with testicular seminoma before and after radiotherapy

Purpose: The evaluation of radiation-induced chromosomal translocations in Peripheral lymphocytes using fluorescent in situ hybridization is a promisi ng method for retrospective dosimetry after a radiation accident. We evalua ted the genomic frequency of chromosomal translocations in patients with te sticular seminoma who received adjuvant radiotherapy to the retroperitoneal lymph nodes, to evaluate the time-effect relationship of radiation-induced stable aberrations after partial body irradiation. Methods: In 13 patients, peripheral lymphocytes could be evaluated before r adiotherapy and at several time points after radiotherapy. In 17 additional patients, lymphocyte samples were obtained after radiotherapy. Thirteen he althy men served as age-matched controls for the aberration frequency befor e radiotherapy. Fluorescent in situ hybridization was performed using whole chromosome probes against chromosomes No. 4, No. 6, and No. 7. Results: Nearly all patients displayed an increased spontaneous rate of gen omic translocations (F-G) before radiotherapy compared to age-matched, heal thy men. The difference was significant in the paired ranks test (p < 0.000 1). After adjuvant radiotherapy, the F-G increased 2- to 8-fold in individu al patients. Within 20 months after radiotherapy, the F-G returned to preth erapeutic levels. Conclusions: The frequency of genomic translocations after partial body irr adiation is time dependent. A persistence of chromosomal aberrations, which is to be expected after total body irradiation, could not be observed. It is likely that the dose and the volume of the irradiated bone marrow are pl aying a role in the persistence of stable chromosomal aberrations. Patients with testicular seminoma displayed an increased frequency of spontaneous g enomic translocations before the initiation of radiotherapy. This chromosom al instability might be related to the known increased rate of secondary ca ncers in this patient group. (C) 2001 Elsevier Science Inc.