Chemotherapy following radium-223 dichloride treatment in ALSYMPCA

Abstract

Background: Radium-223 prolongs overall survival in patients with castration-resistant prostate cancer (CRPC) and symptomatic bone metastases, regardless of prior docetaxel. Whether or not chemotherapy can be safely administered following radium-223 treatment is of clinical importance. An exploratory analysis of prospectively collected data, from the ALSYMPCA (ALpharadin in SYMptomatic Prostate CAncer) patient subgroup who received chemotherapy after radium-223 or placebo treatment, was conducted to evaluate the safety and efficacy of chemotherapy following radium-223.

Methods: In ALSYMPCA, CRPC patients with symptomatic bone metastases and no visceral metastases were randomized 2:1 to receive six injections of radium-223 (50 kBq/kg IV) or placebo plus best standard of care, stratified by prior docetaxel, baseline alkaline phosphatase, and current bisphosphonate use. In this exploratory analysis, chemotherapy agents administered following study treatment were identified; timing and duration were calculated. Hematologic safety was reviewed, and overall survival analyzed.

Results: Overall, 142 radium-223 and 64 placebo patients received subsequent chemotherapy; most common were docetaxel (70% radium-223, 72% placebo) and mitoxantrone (16% radium-223, 20% placebo). The majority of patients (61% radium-223, 58% placebo) had received prior docetaxel. Radium-223 patients started subsequent chemotherapy later than placebo patients; chemotherapy duration was similar between groups. In radium-223 and placebo patients receiving subsequent chemotherapy, median hematologic values (hemoglobin, neutrophils, and platelets) remained nearly constant up to 18 months following start of chemotherapy, regardless of prior docetaxel treatment. A low percentage of patients in both groups had grades 3-4 hematologic values (<10%). Platelet count decline, from last measurement before chemotherapy, was numerically greater in radium-223 versus placebo patients. Median overall survivals from start of chemotherapy were 16.0 and 15.8 months following radium-223 and placebo, respectively.

Conclusions: Chemotherapy following radium-223, regardless of prior docetaxel, is feasible and appears to be well tolerated in patients with CRPC and symptomatic bone metastases. Prostate 76:905-916, 2016. © 2016 The Authors. The Prostate published by Wiley Periodicals, Inc.

Keywords: alpha emitter; bone; chemotherapy; prostate; radium-223; safety.

Figure 1

Consort diagram. *Safety population includes patients who received at least one injection of study drug. One patient in the placebo group received one injection of radium‐223 (week 0) and is included in the radium‐223 safety analysis. †Baseline refers to time of last visit prior to start of first post‐study chemotherapy. Duration of time in study after start of post‐study chemotherapy is defined as time from start of chemotherapy to last registered visit. ‡Percentage of the chemotherapy post‐study drug subgroup (142 radium‐223, 64 placebo).

Figure 2

Maximum percentage decrease from baseline values for hemoglobin (A), neutrophils (B), platelets (C), and platelets by prior docetaxel treatment (D).