Genotoxic effects of radiotherapy and chemotherapy on the circulating lymphocytes of breast cancer patients. I. Chromosome aberrations induced in vivo.

Unstable chromosome aberrations were scored in peripheral blood lymphocytes (PBL) serially collected from 21 breast cancer patients before and after radiotherapy (RT), chemotherapy (CT) and combined treatments. Local radiotherapy as treatment for mammary cancer induced unstable chromosome aberrations in peripheral blood lymphocytes. Only a fraction of these lymphocytes were exposed to irradiation during treatment and the chromosomal damage observed in PBL was equivalent to that induced by irradiation in vitro with 2 Gy at high dose rate, i.e., about 4% of the total dose delivered locally. Chemotherapy alone did not induce such anomalies. Apart from the observed interindividual variations in either the level or the fate of dicentrics with time, different features of chromosome damage were found when chemotherapy was given before or after local cobaltotherapy: secondary chemotherapy did not alter the frequency and the overdispersed distribution of dicentrics observed after first-line radiotherapy; in contrast, when CT was given before radiotherapy, a lower dicentric frequency was scored, the distribution of dicentrics was not always found to be overdispersed and there was a time-dependent decrease in dicentrics after in vivo exposure.