Flow cytometry as a predictive modality in prostate cancer.

Clinical staging and histologic grading do not have sufficient predictive value to determine the response to therapy of any given prostate cancer. A review of the findings from the largest prospective study of patients with localized and locally advanced prostate cancer and from retrospective flow cytometric studies of specific disease stages suggests that DNA flow cytometry offers additional prognostic information for this disease. However, for the individual patient, this added information may have limited value, since approximately 15% of those with diploid disease will experience disease progression within 5 years as compared with half of those with nondiploid disease. We have found that ploidy does not predict length of survival once prostate cancer becomes disseminated, nor does it predict those who will benefit from receiving definitive radiation therapy for localized prostate cancer. On the other hand, for those who have persistent tumor, we have frequently found increased ploidy abnormalities in the tumor sampled after radiation therapy and are currently correlating this finding with clinical outcome. We have also found that DNA flow cytometry can be used to predict tumor volume. For larger, grade-matched diploid tumors, there are significant increases in the proliferation of both the tumor and the adjacent benign tissue, which we take to be evidence of "field effects" in this disease. An even more obvious manifestation of the same phenomenon is seen in the occurrence of aneuploidy in benign tissue near high-grade, large-volume prostate cancer. It is concluded that DNA flow cytometry has much to tell us about the natural history and biologic behavior of prostate cancer.