IS CHROMOSOME IN-SITU SUPPRESSION (CISS) HYBRIDIZATION SUITED AS A PREDICTIVE TEST FOR INTRINSIC RADIOSENSITIVITY IN CANCER-PATIENTS

Chromosome painting (chromosome in situ suppression hybridization, CIS S) analyses were used to control in vitro radiosensitivity of peripher al blood lymphocytes of 70 cancer patients who were assigned to or had just undergone radiation therapy. This technique using three-colour d etection of genomic DNA libraries of chromosomes 1, 2, and 4 was shown to uncover reliably radiation-induced chromosome damage in human peri pheral blood lymphocytes. The lymphocytes of five out of the 70 cancer patients could be defined as to react hypersensitively to in vitro ir radiation. This was particularly underlined not only by the mere incre ase of aberration rate but also by the quality of the induced abnormal ities (e.g. incidence of complex chromosome rearrangements). The same patients were also characterized by extreme radiation reaction in clin ical terms. In spite of some confounding factors, based on the present ed observations, the CISS-technique can be proposed as a predictive te chnique for selecting radiosensitive patients and protecting them from undesired side effects of radiotherapy. A simplification of the scree ning procedure is proposed on the basis of the presented data.