The bone-targeting radioisotope radium-223 has delivered promising results in a randomised trial to test its efficacy in treatment of hormone-refractory prostate cancer (HRPC).
The findings are reported early Online - timed to coincide with presentation of the paper at the American Society of Clinical Oncology meeting in Chicago – and in an upcoming edition of The Lancet Oncology.
Patients who have HRPC often have involvement of bone marrow, leading to symptoms such bone pain, spinal-cord compression and pathological fracture. Existing bone-targeted treatments, such as use of the beta-emitting radioisotope strontium-89 have been shown to reduce bone pain.
Dr Christopher Parker, Institute of Cancer Research and Royal Marsden Hospital, Sutton, UK and colleagues did a study of 64 patients with HRPC. Radium 223 was chosen because it emits alpha radiation – which has higher energy and travels less distance than the beta radiation. Thus Parker and colleagues believe that alpha radiation will have a more pronounced localised effect on tumours.
The patients were randomly assigned to two groups. In the first, 33 received external-beam radiotherapy and up to four injections of radium-223. The other group received the same radiotherapy and placebo.
Levels of bone alkaline phosphatase (bone-ALP) – considered a marker for progression of HRPC – decreased by 66% in the group receiving radium-223. The length of time for patients’ HRPC to progress - as assessed by each prostate-specific-antigen concentration – was much longer for those receiving radium 223 (26 weeks) compared to placebo (eight weeks). The median survival time for radium-223 patients was 41% longer than those receiving placebo (65.3 weeks vs 46.4 weeks respectively); and no Radium-223 patients stopped treatment due to treatment toxicity