Intercellular distribution of cytogenetic changes detected by chromosome painting in irradiated blood lymphocytes of cancer patients

A three-colour chromosome in situ suppression (CISS) hybridization technique (chromosome painting) was used to analyse X-ray-induced chromosome aberrations in peripheral lymphocytes of 83 cancer patients who were assigned to (N = 34) or had just undergone radiation therapy (N = 49). The imperical intercellular distribution of chromosomal aberrations was compared with Poisson distribution and geometric distribution. The impact of complex aberrations on this disributions allowed to discern patients with a high radiation sensitivity from those with an average clinical reaction to therapeutic irradiation. In the group of non-exposed patients, the low mean level of aberrations fitted both distributions in the majority of cases. In contrast, in the group of previously irradiated patients, the geometric distribution in most cases fitted more variants. After an in vitro irradiation of the lymphocytes both groups showed a great interindividual variation between the patients concerning the means and the fit to the distributions, despite similar mean values. The distribution of break points generating the observed spectrum of aberrations, except their variants with low level of mean, did even less fit either of the examined distributions. The use of parameters not only concerning the average number of aberrations or breaks but also their intercellular patterns improved the separation of the previously exposed from the non-exposed, as well as average-reacting patients from radiosensitive patients. The data presented have also documented the high power of the chromosome painting technique in detecting and analysing long-term clastogenic effects as well as complex rearrangements. Examination of these patterns by use of goodnessof-fit tests is expected to offer additional information for discriminating radiosensitive cancer patients.