Detection of circulating prostate specific antigen expressing prostatic cells in the bone marrow of radical prostatectomy patients by sensitive reverse transcriptase polymerase chain reaction

Purpose: The reverse transcriptase polymerase chain reaction (RT-PCR) assay for prostate specific antigen (PSA) expressing cells in the blood circulat ion has been under intense investigation since 1992. Although it has been s uggested that this technology could be used as molecular staging for occult prostatic hematogenous metastases, we have been unable to confirm RT-PCR P SA positivity of peripheral blood to predict stage or recurrence in radical prostatectomy cases. We performed bone marrow RT-PCR PSA assay on a large cohort of radical prostatectomy cases and evaluate the use of this assay in improving prostate cancer staging and detecting early recurrence. Materials and Methods: Unilateral anterior iliac crest bone marrow aspirate s were performed on 116 patients immediately before radical prostatectomy b etween February 1995 and September 1997. Radical prostatectomy specimens we re processed as whole mounts. A sensitive nested RT-PCR assay with specific primers derived from the PSA sequence was used, which enabled us to detect PSA expressing LNCaP prostate cancer cells at the sensitivity of 1 cancer cell per 10 million lymphocytes (1/10(7)). A minimum of 3 RT-PCR PSA reacti ons were performed on all patients and at least 2 positive tests were requi red to define positivity. Patients were followed for PSA recurrence (mean f ollowup 14.7 months). Results: PSA expressing cells were detected in bone marrow of 51 of 116 pat ients (44.0%) when at least 2 of 3 RT-PCR PSA assays per patient were posit ive. A much higher rate of RT-PCR PSA positivity was noted (77/116 patients , 66.3%) when any RT-PCR PSA positivity was considered. In 10 randomly sele cted cases the RT-PCR product was confirmed as PSA by deoxyribonucleic acid sequencing. Of 51 bone marrow RT-PCR positive cases 25 (49%) had organ con fined disease and 26 (51%) had nonorgan confined disease. Similarly, bone m arrow RT-PCR PSA was not associated with age, race, grade, pretreatment PSA or prostatic acid phosphatase value, clinical stage or margin status. Howe ver, the 2-year disease-free survival was 96.6% in RT-PCR negative patients versus 77.5% in RT-PCR positive patients (p = 0.054), and bone marrow RT-P CR PSA was an independent prognostic factor in multivariate analysis includ ing PSA, Gleason grade and pathological stage. Conclusions: Bone marrow RT-PCR PSA positivity in this study did not predic t pathological stage, grade or margin positivity as determined from whole m ount prostate cancer specimens. Furthermore, no relationship with age, grad e or serum markers and bone marrow RT-PCR PSA positivity was noted. However , bone marrow RT-PCR PSA was associated with early disease recurrence. Furt her studies and longer followup are warranted to define the metastatic pote ntial of the PSA expressing cells in the bone marrow of prostate cancer pat ients.