Detection of prostate specific transcripts in the peripheral blood during brachytherapy predicts postoperative PSA kinetics

BACKGROUND. We evaluated whether detection of prostate-specific antigen (PSA) and human kallikrein 2 (hK2) transcripts in the peripheral blood during brachytherapy could predict biochemical outcome. METHODS. Eighty-one patients who underwent ¹²⁵Iodine-based brachytherapy for localized prostate cancer (Gleason score <8, PSA <20 ng/ml, stage <T3), participated in the study. Brachytherapy was given to 35 patients as monotherapy, to 36 in combination with androgen deprivation therapy (ADT), and to 10 in combination with external beam radiation and ADT. Blood samples from 80 patients were available for analysis. Nested RT-PCR means was used to detect mRNA expression of PSA and hK2 in the peripheral blood. Their expression was analyzed before, during and 1 month after brachytherapy. Patients' biochemical outcome (blood PSA levels) during 3 years of follow-up was correlated with the PCR results. RESULTS. The incidence of PSA and hK2 mRNA expression in the peripheral blood was significantly higher during than before or after the procedure. Patients with concurrent positive PSA and hK2 PCR results during brachytherapy had higher postoperative blood PSA values and a slower decline rate of PSA compared with patients with negative PSA and hK2 PCR results. No correlations were found between pre- and postbrachytherapy PCR results and biochemical outcome. ADT was the only significant factor that affected PSA and hK2 mRNA expression during brachytherapy. CONCLUSIONS. Our short-term results suggest that detection of PSA and hK2 transcripts in the peripheral blood of prostate cancer patients during brachytherapy could serve as a predictor of biochemical outcome.