Sensitivity of immunohistochemistry and polymerase chain reaction in detecting prostate cancer cells in bone marrow

Occult micrometastases detected by immunohistochemistry have prognostic significance in patients with localized breast cancer. To determine the usefulness of this technique and of polymerase chain reaction in detecting occult prostate cancer, we evaluated the sensitivity and specificity of immunohistochemistry and polymerase chain reaction amplification of mRNA to detect prostate cancer cells in bone marrow samples. We used cells from an established prostate cancer cell line (LNCAP) mixed with lymphocytes at various dilutions from 10(5) cancer cells in 10(6) lymphocytes to 1:10(6). Both techniques had a 100% specificity and identified cancer cells at all dilutions. Polymerase chain reaction was more sensitive than immunohistochemistry at the lowest dilutions (10(-5) and 10(-6), p = 0.033). We have evaluated seven patients with prostate cancer for micrometastases. Both of the patients with known metastatic prostate cancer and one of the five patients with clinically localized tumors had micrometastases. Detection of micrometastases may be useful in the staging of prostate cancer.