Men with prostate cancer that has spread to the bones may live longer if given a combination of chemotherapy and a bone-targeted radiation drug, according to research reported in the February 3, 2001, issue of the Lancet. While most men survive five years or more with early prostate cancer, those diagnosed at later stages don't live nearly as long. In fact, in cases where prostate cancer has spread to the bones and is resistant to standard hormonal therapy, the average life expectancy is nine months.
The phase II clinical trial, reported in the Lancet, was designed to test the effectiveness of the combination treatment for patients with advanced disease that was no longer responding to hormone treatments. The study showed gains in survival time and pain relief in men who received chemotherapy treatment plus a drug called strontium-89 (Sr-89). Sr-89 is a radioactive substance used to relieve bone pain caused by metastatic prostate cancer. When injected by vein, Sr-89 moves into bones and works by delivering radiation directly to cancer that has spread there.
The study, led by Shi-Ming Tu, M.D., and colleagues from the University of Texas' M.D.Anderson Cancer Center, involved 103 patients who had advanced prostate cancer that was no longer responsive to hormone therapy. In the first part of the study, all patients received an eight-week course of induction chemotherapy (therapy aimed at shrinking the cancer and determining responsiveness to treatment) using the drugs ketoconazole, doxorubicin, estramustine and vinblastine. After completion of induction chemotherapy, those patients whose prostate cancer was responding (72 patients), went on to enter the second part of the study in which they received consolidation chemotherapy consisting of doxorubicin for six weeks. (Consolidation therapy is treatment given after induction therapy to reduce the number of cancer cells even further.) At this point, patients were also randomly assigned to receive a single dose of Sr-89 or a placebo in addition to the doxorubicin.
On average, the group of 36 patients that received the Sr-89 lived almost a year longer than the group that did not receive it. Of the 103 initial patients in this study, 67 have died. The average survival time for all 103 patients was 18 months. Of the 36 patients who went on to receive consolidation therapy and Sr-89, 22 are still alive and the average survival is 28 months. Of those 36 patients who received consolidation therapy without Sr-89, 27 have died and the average survival time is 17 months.
The study's authors noted that although the results require confirmation, they do strongly support the hypothesis that a bone-targeted consolidation therapy containing Sr-89 improves the clinical outcome of patients with advanced prostate cancer. In previous studies, Sr-89 had not been shown to change the course or prognosis of advanced prostate cancer. In an editorial in the same issue of the Lancet, Alexandre Zlotta of the University Clinics of Brussels, Belgium, wrote that the study does not provide definite answers about the beneficial effect of doxorubicin and strontium, but does give researchers strong justification to study more bone-targeted therapies in advanced cases of prostate cancer. While the improvement in survival with Sr-89 was statistically significant, further studies with larger patient populations will be required to compare this promising combination against the hormonal treatment now commonly used for distant metastatic prostate cancer.