Chromosome aberrations in the peripheral lymphocytes induced by brachytherapy and external cobalt teletherapy.

In the present study, the induction efficiencies of chromosome aberrations were analyzed in patients receiving various modalities of interstitial radiotherapy with small radiation sources in the oral cavity area and compared with those in patients treated with external telecobalt irradiation in the thoracic region. Further, as a local nonstochastic effect, the acute mucosal reaction was investigated. The mucosal reaction in the area treated by brachytherapy reached a maximum at two to three weeks after the implantation. The frequencies of dicentrics plus rings of peripheral lymphocytes, on the other hand, revealed rapid increases and approached plateau levels as early as two days after the implantation. The whole-body effects, evaluated on the basis of the chromosome aberration frequencies of peripheral lymphocytes in the patients who underwent brachytherapy, were compared with the effects observed in those patients treated with external radiotherapy or bleomycin injection and discussed with regard to their effectiveness in control of the tumor and side effects. The radiation doses used in the patients who received brachytherapy or a single external irradiation were found to exert the same effects on the chromosome aberration induction. However, even in the case of brachytherapy in which whole-body side effects were believed to be trivial, the peripheral lymphocyte count was temporarily reduced to one half or less of the preirradiation level. An equivalent whole-body dose of 50 cGy was obtained from the frequencies of dicentrics and rings.