Background: Patients with advanced prostate cancer eventually cease to respond to hormonal therapy and thus progress to hormone refractory prostate cancer (HRPC). Prednisone has been used in this setting; however, limited data is available for this monotherapy in the asymptomatic HRPC population.
Objective: To evaluate the PSA response rate to prednisone in asymptomatic patients with hormone refractory prostate cancer (HRPC). Secondary objectives were to determine toxicity, predictors of response, and to determine overall survival of this population.
Methods: Patients with asymptomatic HRPC that were treated with low dose prednisone from April 1998 to 2003 were identified from the British Columbia Cancer Agency patient and pharmacy registries. Inclusion criteria were an ECOG Performance Status of 2 at the time of prednisone initiation, prior medical or surgical orchidectomy, a rising PSA, and no symptoms from prostate cancer. Demographic data, lab values, serial PSAs, and survival data were collected. Univariate analyses were performed to evaluate potential predictors of response.
Results: Forty-nine patients met the inclusion criteria. There was a 22.4% response rate to prednisone as defined by a 50% PSA decline. An additional 16.3% of patients had a PSA decline of < 50%. Ninety percent of patients had no documented side effects. PSA responders were more likely to have bony metastases (9/11 versus 17/38, p = 0.03) and lived longer (24.7 versus 15.4 months median survival p = 0.02). The median duration of response in the PSA responders was 4.3 months (0.89-30). Of all PSA responders, 27% had a time to progression greater than 1 year and 45% did not require chemotherapy for the duration of the study.
Conclusion: Prednisone monotherapy is well tolerated and is associated with a clinically relevant response rate in patients with asymptomatic HRPC. Prolonged time to progression and thus avoidance of more toxic chemotherapy is possible in some patients.