Changes in alkaline phosphatase (ALP) dynamics and overall survival (OS) in metastatic castration-resistant prostate cancer (mCRPC) patients treated with radium-223 in an international early access program (EAP)

Background

Identifying a reliable marker of efficacy for radium-223 dichloride (Ra-223) would aid in the clinical management of mCRPC patients (pts). In exploratory analyses of mCRPC pts with symptomatic bone metastases treated with Ra-223 in the ALSYMPCA trial, OS was significantly longer in pts with a confirmed decline in ALP levels from baseline at week 12, compared with pts without a confirmed ALP decline. Here, we present data on ALP dynamics and OS and time to first symptomatic skeletal event (SSE) in pts treated with Ra-223 in an international EAP.

Methods

This was a prospective single-arm phase IIIb study of CRPC pts with symptomatic or asymptomatic bone metastases (no visceral disease) recruited from 14 countries. Pts received Ra-223 50 kBq/kg (55 kBq/kg after NIST update) iv, every 4 weeks for up to 6 cycles. Co-primary endpoints were safety and OS. Exploratory analyses investigated whether a confirmed decline (any magnitude) in ALP levels was associated with OS and time to first SSE.

Results

696 pts received at least one Ra-223 cycle. Of those, 398 (57%) pts had a confirmed decline in ALP and 298 (43%) had no confirmed ALP decline. Key baseline characteristics are shown (Table). More pts with a confirmed ALP decline (374, 94%) received 5–6 Ra-223 injections than those with no ALP decline (99, 33%). Hazard ratios (HR) for confirmed ALP decline at week 12 vs no decline suggest a strong association of ALP decline with both longer OS (HR 0.299, 95% CI 0.227–0.395) and longer time to first SSE (HR 0.474, 95% CI 0.340–0.662) (Table).

NR/A, not reached/available. ^aMeasured from the brief pain inventory short form.^bCalculated from Cox proportional hazards model.

Conclusions

In this EAP, which is relevant for pts currently treated in clinical practice, decline in ALP was associated with longer OS and time to first SSE.

Clinical trial identification

ClinicalTrials.gov NCT01618370

Legal entity responsible for the study

Pharmaceutical Division of Bayer

Funding

Pharmaceutical Division of Bayer

Disclosure

D. Heinrich: Grant from Bayer, during the conduct of the study; personal fees from Bayer, Amgen, Astellas, Sanofi, and Johnson & Johnson, outside the submitted work.

S. Gillessen: Advisory Boards (compensated): Astellas, Bayer, Curevac, Dendreon, Janssen Cilag, Janssen Diagnostics, Millennium, Novartis, Orion Pharma, Pfizer, Sanofi Aventis. Speakers Bureau (without honorarium): Bayer. Pending patent application: WO 2009138392 A1.

A. Heidenreich: Grants and personal fees from Bayer during the conduct of the study; grants and personal fees from Astellas and Sanofi Aventis, personal fees from Amgen, Dendreon, Ferring, Hexal, IPSEN, Janssen-Cilag, Pfizer, and Takeda; outside the submitted work.

J.M. O'Sullivan: Advisory boards for: Bayer, Astellas, Sanofi.

J. Carles: Scientific advisory board membership/consultancy: Johnson & Johnson, Astellas, Bayer, Amgen, Pfizer, BMS; Speakers Bureau: Bayer, Johnson & Johnson.

M. Wirth: Personal fees from Apogepha, Astellas, Bayer, Janssen-Cilag, Merck, Roche, and Sanofi-Aventis outside the submitted work.

K. Miller: Advisory board membership: Bayer.

J. Gratt: Personal fees from Bayer Healthcare during the conduct of the study.

M. Serger-van Tol: Employment: Bayer.

S. Nilsson: Participated in Bayer Healthcare advisory boards and as speaker in scientific meetings.

F. Saad: Grants, personal fees and non-financial support from Bayer, Amgen, Janssen, and Astellas, during the conduct of the study.

All other authors have declared no conflicts of interest.