The histology of radiation therapy effect on prostate adenocarcinoma as assessed by needle biopsy after brachytherapy boost. Correlation with biochemical failure.

Abstract

Brachytherapy boost with external radiation therapy (RT) allows safer delivery to the prostate than conventional techniques. We measured the degree of radiation effect of adenocarcinoma cells in post-RT biopsy specimens and the association with biochemical failure. Forty-six patients with T2b-3c adenocarcinomas underwent 18-month post-RT biopsies, of whom 22 had adenocarcinoma. All biopsy specimens without obvious adenocarcinoma were stained with antibodies to prostate-specific antigen and keratins AE1/AE3 and 34 beta E12. The RT effect to adenocarcinoma cells was scored by adding the scores of the nuclear and cytoplasmic changes. Each adenocarcinoma was assigned 2 scores; the most-common and the least-amount RT effect. Treatment for 7 of the 46 patients failed; 6 of these had residual adenocarcinoma on the post-RT biopsy specimen. Sixteen of 22 patients with adenocarcinoma on the post-RT biopsy specimen did not experience biochemical failure. The presence of adenocarcinoma on the post-RT biopsy specimen was significantly associated with failure. The mean most-common RT-effect score for the 16 patients without failure was 5.2 compared with 4.2 for the 6 patients with failure. The mean least-amount RT-effect score in patients without failure was 4.4 compared with 2.8 (range, 2-4; SD, 0.75) in the failure group. These relatively radiation-resistant foci may be the source of failure. Scoring the RT-effect of adenocarcinoma in post-RT biopsy specimens may be clinically useful in predicting subsequent biochemical failure.