[DNA ploidy and proliferating cell nuclear antigen positivity rate as predictive indication of effectiveness of preoperative radiation].

We compared histological effects following radiotherapy in relation to the DNA ploidy pattern and the proliferating cell nuclear antigen (PCNA) positivity rate in 37 patients with rectal cancer who underwent preoperative radiation therapy. Twelve of 23 cases in which the PCNA positivity rate before irradiation was more than 25% showed the effectiveness of radiotherapy (52.2%), against 2 of 6 cases with a rate of less than 25%. Cases in which the rate was more than 25% tended to show more effectiveness. Seventeen of 23 cases in which the PCNA positivity rate was more than 25% showed a decrease in PCNA positivity rate (73.9%). The rate in 6 cases showed no change, and no cases had an increase. In particular, in 12 cases in which the PCNA positivity rate was more than 55%, half showed effectiveness, and the PCNA rate decreased 20% on average. The PCNA positivity rate tended to decrease as a result of irradiation, and especially in diploid cases there were significant differences in the rate before and after irradiation. We suggest that cases in which the PCNA positivity rate is more than 55% with diploid DNA pattern would show most effect. The effects of irradiation could be predicted with biopsy materials and by measuring the DNA ploidy pattern and the PCNA positivity rate.