Minimal Residual Disease in Prostate Cancer

Detection of minimal residual disease (MRD) in prostate cancer over several decades has greatly informed our understanding of dissemination and recurrence, but has not yet been routinely used in clinical care. Investigators have detected MRD by identification of prostate cancer cells in the bone marrow; termed disseminated tumor cells (DTCs) and blood; termed circulating tumor cells (CTCs). Various techniques including PSA-RT PCR, PSA immunocytochemistry, cytokeratin immunocytochemistry, and immune-magnetic depletion of hematopoietic cells followed by EPCAM based positive selection, have been used. Importantly, detection of DTCs correlates with recurrence. Research into prostate cancer CTCs has intensified recently, but their use in MRD evaluation has been more limited. Investigators are using semi-automated platforms to detect and begin to study prostate cancer CTCs in patients with no evidence of disease. PSA immunocytochemistry also detects CTCs and correlates with recurrence. Emerging technologies have the potential to greatly aid research in this exciting field.