Characterization of residual tumor cells following radical radiation therapy for prostatic adenocarcinoma; immunohistochemical expression of prostate-specific antigen, prostatic acid phosphatase, and cytokeratin 8

Abstract

Background: Our knowledge about the nature and biological activity of tumor cells residing in the prostate gland after radical radiotherapy (RRT) is limited.

Methods: In the present study, residual tumor in core biopsies taken from 37 patients after an average of 6.8 years follow-up after radiation, were investigated with immunohistochemistry for the biochemical markers prostate-specific antigen (PSA), prostatic acid phosphatase (PAP), and the epithelial marker, cytokeratin 8 (CK8).

Results: Tumor cells were cytokeratin-positive in 33 of 34 evaluable specimens (97%). PSA and PAP were expressed in the tumor cells in 94% (34/36) and 81% (30/37) of cases, respectively. No significant correlation was observed between PSA/PAP expression and tumor grade after treatment. Endocrine treatment administered in addition to RRT in 12 of the 37 patients did not affect the expression of PSA or PAP. The expression of both biochemical markers was reduced after radiotherapy in 10 of the 12 cases for which pre- and post-treatment specimens were available.

Conclusions: Tumor cells retain their epithelial characteristics immunohistochemically after radiation, though their morphology sometimes suggests an altered phenotype after treatment. PSA and PAP reactivity was demonstrated in tumor cells nearly 7 years after radiotherapy, which indicates that these cells maintain their biochemical integrity and protein synthesis to a certain extent. Furthermore, endocrine treatment did not abolish PSA or PAP expression in the tumor cells. Whether PSA and PAP immunoexpression provides independent prognostic information needs to be further investigated.