Background: Chemotherapy has emerged as a standard treatment in patients with castration-refractory prostate cancer (CRPC). Consensus criteria are available to define response in CRPC as at least a 50% decline in serum prostate-specific antigen (PSA) confirmed 4 weeks later. The objective of this work was to study early serum PSA changes in patients under chemotherapy and to correlate these changes with subsequent response assessment.
Patients and methods: Serum PSA levels were monitored every 3 weeks in 79 patients with CRPC treated with chemotherapy and a time course of serum PSA levels was obtained. Correlation with response was studied.
Results: According to consensus criteria, 21 (40%) and 20 (38%) patients achieved a PSA response and stabilization, respectively, after first-line chemotherapy. Among patients who achieved either a response or a stabilization, 8 of 41 (20%) had a serum PSA rise during the first 8 weeks of chemotherapy, followed by a subsequent decline in serum PSA. The same observation was made in patients receiving second-line chemotherapy: 6 of 20 patients achieving a response or stabilization had an initial serum PSA rise. The postchemotherapy increase in serum PSA could reach more than twice the baseline value. The duration of the PSA surge ranged from 1 to 8 weeks. When considering responders only, 6 of 30 (20%) had a postchemotherapy serum PSA surge, followed by a drop.
Conclusion: Postchemotherapy PSA surges occur not infrequently in patients with CRPC who respond to chemotherapy. Physicians should be aware of this effect to avoid inadequate early discontinuation of chemotherapy.