Early PSA Response as a Prognostic Factor in Metastatic Prostate Cancer
Prognostic models for overall survival (OS) for patients with metastatic castration-resistant prostate cancer (mCRPC) are dated and do not reflect significant advances in treatment options available for these patients (Halabi S, et al. J Clin Oncol. 2014;32:671-677). Thus, Fuerea and colleagues reported on a study to determine the clinical significance of an early prostate-specific antigen (PSA) response during the first 4 weeks of therapy with next-generation androgen pathway inhibitors (enzalutamide, abiraterone acetate, or TAK-700) for men with mCRPC (Fuerea A, et al. ESMO 2014: Abstract 796P).
In this retrospective analysis, early PSA response (defined as a reduction in PSA of ?30% from baseline) was assessed in 118 patients with mCRPC who were treated with enzalutamide in the AFFIRM and the PREVAIL trials, abiraterone acetate in the COU-AA-301 and COU-AA-302 studies, and TAK-700 in the C21004 and C21005 trials. The PSA values were obtained at baseline and 28 days (±7 days) after the initiation of therapy. The effects of patient, tumor, and treatment characteristics on progression-free survival (PFS) and OS were determined.
The median PFS times were 13.9 months and 5.6 months for patients with and without an early PSA response, respectively (P <.001). The median OS was 32 months in patients with an early PSA response compared with 16 months in patients without an early PSA response (P <.01), and this difference remained significant in multivariate analyses that included pretherapeutic factors for mCRPC (ie, ECOG score; visceral metastases or pain; serum albumin, alkaline phosphatase, hemoglobin, and lactic dehydrogenase levels).
Fuerea and colleagues concluded that early PSA response within 28 days of the initiation of therapy is an independent prognostic factor in patients with mCRPC who were treated with next-generation androgen pathway inhibitors, and may be useful in providing personalized therapy to these patients.