Role of time to PSA progression as prognostic factor for overall survival in new therapeutic agents for treatment of patients with metastatic hormone-refractory prostate cancer

Giandomenico Roviello

Medical Oncology Unit, University of Siena, Policlinico Le Scotte, Viale Bracci 11, 53100 Siena, Italy.

E-mail: giandomenicoroviello@hotmail.it; Fax: +390577586139

Accepted 09 October, 2013

Abstract

Metastatic castration-refractory prostate cancer (mCRPC) is a heterogenous disease, with wide variation in clinical response to hormone manipulation and chemotherapy. More recently, several therapies (Cabazitaxel (Cbz), Abiraterone Acetate (AA) and Enzalutamide (E) have been approved for the management of the mCRCP after Docetaxel failure. Although, Prostate-specific antigen (PSA) has been the most studied biomarker in prostate cancer, little studies described its trend during the administration of one of these new therapies. In order to verify the role of PSA as prognostic marker for patients exposed to Cbz, AA, E, we analyzed the data of repsonse of PSA (PSA response rate (PSA RR) and time to PSA progression (TTPP) reported in the phase III TROPIC, AFFIRM and COU-AA-301 trail. We also established Δ OS (overall survival) by subtracting the value of each OS from the respective value of time to PSA progression. All trails did not fail their primary end point. In regard of Δ OS, we noted a mayor value in the Cbz and E trail (8.7 and 10.1 months), in contrast we observed a minor value in the AA trail (5.6 months). These findings could suggest that an increase of PSA during AA therapy might predict a poor prognosis only for AA.  In conclusion, although, our results can not be conclusive, a revision of PSA as prognostic marker is required for the novel agents (Cbz, E, and AA). Meanwhile, we deem that a close monitor of PSA seems particularly important for patients treated with AA and less important during E-based therapy.

Keywords: Cabazitaxel, Abiraterone Acetate, Enzalutamide, Prostate-specific antigen (PSA)