Targeted Radioisotope Therapy Extends Life for Prostate Cancer Patients
Prostate cancer patients with advanced tumors that have spread to bone have a poor prognosis; men with castrate-resistant prostate cancer generally live three to five years after diagnosis. According to the National Cancer Institute, an estimated 238,500 men will be diagnosed with prostate cancer in 2013, and 29,700 will die from the disease.
In the past 25 years, many bone-targeted drugs have been developed to treat advanced prostate cancer, but they have more of a palliative effect, treating pain, but not necessarily prolonging survival. Radium-223 dichloride, a new targeted radioisotope therapy anticipated for U.S. Food and Drug Administration (FDA) approval this spring, has shown promising results reducing pain from bone metastases and increasing the survival of these patients.
Radium-223 concentrates in bone metastases and releases alpha particles that are deadly to tumors. The alpha particles have a short range of penetration, sparing nearby healthy tissues and essential bone marrow. The European phase III ALSYMPCA (ALpharadin in SYMptomatic Prostate CAncer) trial utilized a double-blind and randomized design and showed an extended overall survival benefit of 44 percent, with patients living about 14 months longer in the treated group versus 11 months in the placebo group.
In addition to prolonged survival, those treated with Radium-223 also experienced delayed onset of complications due to bone metastases. Therapy monitoring is made possible with scintigraphy and PET, which provide information about biological processes, including those involved in cancerous tumors.
Radium-223 has been shown to be well tolerated. Serious side effects are infrequent, and the risk of bone marrow suppression is low even in patients who have been heavily pretreated with chemotherapy. Due to its improved outcomes in preplanned interim analysis, the ALSYMPCA trial was terminated early. In February, Radium-223 was granted priority review by the FDA.
Several education sessions will be offered on the topic of Radium-223 at the Society of Nuclear Medicine and Molecular Imaging’s (SNMMI) 2013 annual meeting. The Henry N. Wagner, Jr. Lectureship, entitled “Moving Molecular Radiotherapy into the Mainstream: Have We Reached the Tipping Point?” presented at the June 9 plenary session, will be given by Val Lewington, MD, of King’s College London. An SNMMI technologist section course on “Therapy/Oncology” and several scientific sessions and posters on the topic also will be presented at the meeting.
This is an exciting time for nuclear medicine as alpha radiation is not routinely used as a treatment. Preliminary results are encouraging and many patient and referring physician organizations have expressed interest in the new therapy. While Radium-223 offers a better standard of care for patients with advanced prostate cancer, in the future we may also see its potential to help patients with other forms of cancer.
About the author: Iagaru is assistant professor of radiology - nuclear medicine, Stanford University Medical Center, and SNMMI outreach committee co-chair and targeted radioisotope therapy outreach working group co-chair.