Deoxyribonucleic acid ploidy in the irradiated prostate

Abstract

A retrospective study was performed to determine whether the ploidy of localized prostate cancer was correlated with the response to radiation therapy. Prostate tissue was obtained from 69 patients prior to and at least 22 months following definitive radiation therapy. A positive postradiation biopsy of a hypoechoic lesion obtained under transrectal ultrasound guidance was taken as evidence of a failure to respond to therapy. Only 20% of these patients had negative posttherapy biopsies. This poor response rate was similar, regardless of whether the pretreatment tumor was diploid or aneuploid. Treatment failure was correlated with an increased incidence of aneuploid histograms after therapy. Prior to therapy, 80% of the tumors were diploid; after therapy, only 56% were diploid, whereas nontetraploid-aneuploid tumors had increased 3-fold. Among 44 patients who had diploid tumors prior to therapy, the residual prostate cancer was tetraploid in five cases and nontetraploid-aneuploid in ten cases.