Purpose: We identified variables associated with a positive prostate biopsy after salvage cryotherapy in patients in whom initial external beam radiotherapy for prostate cancer failed to improve our cryotherapy technique, optimize local control and improve our patient selection criteria for salvage cryotherapy.
Materials and methods: Between July 1992 and January 1995, 145 patients underwent salvage cryotherapy. Post-cryotherapy sextant prostate biopsies were performed in 107 cases. We evaluated certain variables on univariate and multivariate analysis as predictors of a positive biopsy after cryotherapy, including the type of previous therapy, tumor stage and grade at initial diagnosis, prostate volume, pre-cryotherapy prostate specific antigen (PSA), number of positive biopsy cores before cryotherapy, PSA nadir after cryotherapy, stage and grade of local recurrence, number of cryoprobes, number of freeze-thaw cycles and use of a urethral warming catheter during cryotherapy.
Results: Biopsies were positive in 23 cases (21%) after salvage cryotherapy. Variables associated with a positive biopsy on univariate analysis were initial stage, precryotherapy PSA, PSA nadir after cryotherapy, number of cryoprobes, number of freeze-thaw cycles and a history of chemotherapy (p = 0.005, 0.027, 0.001, 0.009, 0.018 and 0.008, respectively). Variables that remained associated with a positive biopsy on multivariate analysis were the number of probes used and post-cryotherapy PSA nadir (p = 0.013 and 0.019, respectively).
Conclusions: Patients with initial clinical stage T1-2N0M0 disease and PSA no more than 10 ng./ml. have a higher rate of negative biopsies after salvage cryotherapy. Therefore, they are better candidates for salvage cryotherapy for locally recurrent prostate adenocarcinoma after external beam radiotherapy. To optimize the potential for local control the technique of salvage cryotherapy should include 2 freeze-thaw cycles and a minimum of 5 cryoprobes. Detectable PSA after salvage cryotherapy is a strong predictor of local failure.