Predictive assays for the therapy of rectum carcinoma.

Cytofluorometric DNA measurements showed that about 55% of rectum carcinoma (129 patients) had tumours with an abnormal DNA content (DNA aneuploidy). For patients with such a tumour the prognosis was worse than for patients with DNA diploid tumours. From the DNA histograms the number of S-phase cells was calculated. In tumours with the stage pT3, which disseminated to lymph nodes or metastasized, a higher number of S-phase cells was found than in tumours with the staging pT3N0M0. In all untreated tumours cells with micronuclei were found. This demonstrated cell loss. In most tumours this effect was considerable. The ratio:number of S-phase cells/number of cells with micronuclei may allow a rough estimate for cell turnover. In patients with a bad prognosis and in those patients who had a local recurrence after resection of the tumour this ratio was high. In 34 patients the parameters were measured before and after preoperative radiotherapy. In some tumours a rapid increase of S-phase cells occurred after irradiation, this effect might express repopulation. In these patients a local recurrence was frequently found. From the data obtained so far a prediction for local recurrences might be possible from the determination of nuclear protein bound SH-groups. The determination of micronuclei indicated that it can be used as a measure for radiation response in tumours. All parameters show a high variability between individual tumours. A further study is useful whether the measured parameters are suitable as predictors.