Outcomes and predictive factors for biochemical relapse following primary androgen deprivation therapy in men with bone scan negative prostate cancer

Abstract

Primary androgen deprivation therapy (PADT) is an important treatment modality for men with localized or locally advanced prostate cancer and without bone metastasis. There is, however, a lack of data on the biochemical relapse (BR) outcomes in these patients. Here, we studied the outcome of a contemporary series of men treated by PADT and investigated predictive risk factors for BR. One hundred and fifty-five patients treated by PADT formed the initial study cohort, and BR outcomes in this group were reviewed. The outcomes of men with bone scan negative disease were specifically analysed. The predictive value of a panel of clinical risk factors for BR was evaluated using univariate and multivariate analysis. The results were further validated in a separate cohort of patients without bone metastasis from a second institution (n = 84). Median follow-up was 70 months. In the first study cohort, 109/155 men (70%) had bone scan negative disease. In these patients, only 45% developed BR during the follow-up period with only 28% relapsing within 5 years of initiating PADT. Key-independent factors predicting BR were a high PSA nadir (p = 0.001) and a shorter time to nadir (p < 0.001). A nadir of ≤0.1 ng/ml and time to nadir of >24 months specifically identified men with a very good outcome from PADT. In a second-independent cohort, very similar overall and 5-year BR rates were observed in men without bone metastasis (39 and 35%, respectively). PSA nadir thresholds identified in the first cohort were again able to define a good prognostic group in this re-test cohort (p = 0.005 and p = 0.01, respectively). Men treated by PADT and without bone metastasis can have very durable responses to PADT with the majority remaining BR free at 5 years. PSA nadir and time to nadir are key predictors of a good outcome in this group.