PREDICTIVE VALUE OF PROSTATE SPECIFIC ANTIGEN NADIR AFTER SALVAGE CRYOTHERAPY

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Abstract
We determined nadir prostate specific antigen (PSA) after salvage cyrotherapy to distinguish patients who are potentially cured from those at risk for subsequent biochemical and biopsy proved failure. A total of 146 patients who underwent salvage cyrotherapy were followed a median of 21 months (range 3 to 47) with regular serum PSA analysis and digital rectal examination. Sextant biopsies were performed at 6 months or earlier when PSA increased greater than 2 ng./ml. from the nadir value (biochemical failure) or there was a palpable local recurrence. We compared the incidence of biochemical failure and biopsy specimens positive for cancer to pretreatment PSA and posttreatment nadir PSA. In 59 of the 146 patients (40%) PSA decreased to an undetectable level within a median of 3 months. In 85 of the 109 patients (78%) who underwent biopsy the specimens were negative for cancer. Low serum PSA nadir values were associated with low pretreatment PSA and a low incidence of biochemical failure. In 6 of 60 patients (10%) in whom PSA nadir was 0.5 ng./ml. or less and in 18 of 49 (37%) with a higher PSA nadir biopsy was positive for cancer. A PSA nadir of 0.5 ng./ml. or less should be achieved after salvage cryotherapy. Higher nadirs are more likely to be associated with increasing posttreatment PSA and positive biopsies. PSA nadir is a better prognostic indicator of biochemical and biopsy proved failure after salvage cryotherapy than pretreatment PSA.