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

A three-colour chromosome in situ suppression (CISS) hydridization techniqu e (chromosome painting) was used to analyse X-ray-induced chromosome aberra tions in peripheral lymphocytes of 83 cancer patients who were assigned to (N = 34) or had just undergone radiation therapy (N = 49). The imperical in tercellular distribution of chromosomal aberrations was compared with Poiss on distribution and geometric distribution. The impact of complex aberratio ns on this distributions allowed to discern patients with a high radiation sensitivity from those with an average clinical reaction to therapeutic irr adiation. In the group of non-exposed patients, the low mean level of aberr ations 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 lymph ocytes both groups showed a great interindividual variation between the pat ients concerning the means and the fit to the distributions, despite simila r mean values. The distribution of break points generating the observed spe ctrum of aberrations, except their variants with low level of mean, did eve n 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 fr om the non-exposed, as well as average-reacting patients from radiosensitiv e patients. The data presented have also documented the high power of the c hromosome painting technique in detecting and analysing long-term clastogen ic effects as well as complex rearrangements. Examination of these patterns by use of goodness-of-fit tests is expected to offer additional informatio n for discriminating radiosensitive cancer patients.