LIMITATIONS IN THE USE OF SERUM PROSTATE SPECIFIC ANTIGEN LEVELS TO MONITOR PATIENTS AFTER TREATMENT FOR PROSTATE CANCER

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Abstract
We reviewed the literature to help clarify the benefits and/or hazards associated with monitoring serum prostate specific antigen (PSA) after treatment with surgery or radiation therapy (RT) for nonmetastatic prostate cancer. A search was performed for 1990 to 2004 using the MEDLINE database, CancerLit database and reference lists of relevant studies to obtain articles addressing the use of serum PSA to follow patients after treatment for prostate cancer. Studies were reviewed to determine 1) if serial PSA monitoring provides an early and accurate surrogate assessment of cancer cure or treatment failure, 2) if any pattern in the PSA profile after treatment provides conclusive evidence of early local vs systemic failure, 3) the magnitude of the lead time to clinical failure that serial PSA monitoring may provide and 4) if the early identification of biochemical failure (BF) with earlier intervention improves outcome. Although a lower PSA nadir after treatment with RT has been associated with cancer cure, 5% to 25% of patients ultimately have failure (beyond 5 years) even with the most optimal biochemical response. The most appropriate BF definitions to use after treatment for prostate cancer with RT remains controversial due to substantial differences in their accuracy, sensitivity, specificity and positive predictive value for clinical outcome. No pattern of PSA kinetics after treatment has conclusively been associated with a specific recurrence site. Biochemical failure definitions in patients treated with RT appear to provide a 6 to 18 month lead time to clinical failure but there are only limited published data to suggest that early intervention of any type (androgen deprivation, RT, surgery, etc) impacts survival. The overall benefit of monitoring serum PSA after treatment for prostate cancer remains controversial. Considering the potential dangers associated with incorrectly assuming the efficacy of new forms of treatment, the toxicity of administering salvage therapies of uncertain efficacy after BF has been identified and the anxiety associated with tracking posttreatment serum PSA, additional studies must be done to determine the appropriate use of this marker in properly treating patients after therapy.

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