Optimizing patient selection for prostate monotherapy

Abstract

Purpose: Patients at low risk for prostate-specific antigen (PSA) failure following definitive local therapy are those with PSA of 10 or less, biopsy Gleason Score of 6 or less, and 1992 American Joint Committee on Cancer (AJCC) clinical Stage T1c or T2a. However, low-risk patients managed with radical prostatectomy and found to have prostatectomy Gleason score ≥ 3+4 have a less favorable PSA outcome when compared to patients with prostatectomy Gleason score ≤ 3+3. This study was performed to determine whether the percentage of positive prostate biopsy cores could predict upgrading from a biopsy Gleason score of 6 or less to a prostatectomy Gleason score ≥ 3+4 in low-risk patients to optimize selection for prostate only radiation therapy. Methods and Materials: Concordance testing of the biopsy Gleason score and the primary and secondary prostatectomy Gleason grades was performed in 427 prostate cancer patients treated with radical prostatectomy and at low risk for PSA failure. Logistic regression multivariable analysis was performed to test the ability of the established prognostic factors and the percentage of positive prostate biopsies (<34%, 34–50%, >50%) to predict for upgrading from biopsy Gleason score of 6 or less prostatectomy Gleason score ≥ 3+4. PSA failure-free survival was reported using the actuarial method of Kaplan and Meier and comparisons were made using a log–rank test. Results: Twenty-nine percent of the 427 study patients were upgraded from a biopsy Gleason score of 6 or less to a prostatectomy Gleason score ≥ 3+4. The presence of greater than 50% positive biopsies was the only significant factor for predicting the upgrading from biopsy Gleason score of 6 or less to prostatectomy Gleason score ≥ 3+4 on logistic regression multivariable analysis with the variables treated as continuous and categorical. Specifically, upgrading occurred in 26% vs. 59% of patients with 50% or less vs. greater than 50% positive biopsies, respectively. This translated into a 5-year PSA failure-free survival which was significantly higher (92% vs. 62%, p = 0.00001) for men with 50% or less vs. greater than 50% positive prostate biopsies, respectively. Conclusion: The presence of greater than 50% positive biopsies was associated with higher rates of pathologic upgrading which translated into lower 5-year PSA failure-free survival following radical prostatectomy (RP). Therefore, the percentage of positive biopsies may be useful in optimizing the selection of low-risk patients for prostate only radiation therapy such as external beam radiation or implant monotherapy.