Deoxyribonucleic acid flow cytometry in predicting response to radical radiotherapy of bladder cancer

Using flow cytometry tumors can be classified according to their deoxyribonucleic acid content as diploid or aneuploid with 1 or several cell lines and to the ploidy level of the aneuploid cell lines, as well as to the proportion of proliferating cells. We used this technique in 73 patients with invasive transitional cell carcinoma of the bladder who received radical radiation therapy with followup of surviving patients for at least 5 years. The effects of therapy were related to the deoxyribonucleic acid patterns before irradiation. All diploid tumors disappeared, while aneuploid tumors with 1 cell line disappeared in 55% and those with several cell lines in 30% of the patients. Aneuploid tumors with cell lines exceeding 4c appeared to be more radiosensitive than those in the triploid region. Thus, tumors unresponsive to therapy as well as those that recurred after irradiation were mostly triploid. Since most of the tumors had high proliferation rates the proportion of S-phase cells was of only limited value for further classification of the various tumors. In the choice between radical radiotherapy, in which bladder function is maintained, and cystectomy an analysis of tumor ploidy provides at least some basis on which radiation response can be predicted. In the choice of therapy we must also consider the fact that almost 20% of the patients who failed to respond to therapy revealed aneuploidy only in bladder washings after irradiation, indicating existence of concomitant carcinoma in situ.