Six months of neoadjuvant treatment with the targeted agent Zytiga® (abiraterone) plus hormonal therapy eliminated or nearly eliminated tumors in one-third of men with localized high-risk prostate cancer, according to the results of a study presented at the 2012 annual meeting of the American Society of Clinical Oncology (ASCO) in Chicago, Illinois.
Men with localized prostate cancer can often be cured with surgery or radiation alone; however, men with certain risk factors—such as a high Gleason score, very high PSA level, spread of cancer outside the prostate, and lymph node involvement—tend to have a high recurrence rate regardless of whether all detectable cancer is surgically removed and/or radiated. These men have what is referred to as localized high-risk prostate cancer (LHRPC). Men with LHRPC tend to have a poor prognosis—it is infrequently cured with radical prostatectomy (RP) and neoadjuvant hormonal therapy (androgen deprivation therapy, or ADT) has not been shown to improve outcomes.
Zytiga is an oral targeted agent that blocks the production of androgens (male hormones such as testosterone) not only by the testes, but also by the adrenal glands and the tumor itself. Zytiga is approved in combination with prednisone for the treatment of metastatic, hormone-refractory prostate cancer that has previously been treated with chemotherapy. The current study marks the first time that the drug has been investigated in earlier stages of prostate cancer and in the neoadjuvant (pre-surgical) setting.
The randomized phase II study included 56 men with LHRPC who were randomized to one of two groups. Group A included 27 men who received leuprolide hormonal therapy for 12 weeks followed by leuprolide plus Zytiga for another 12 weeks. Group B included 29 men who received Zytiga and leuprolide for the entire 24-week period. All men underwent prostate surgery after 24 weeks of therapy and the tissue was then examined for evidence of cancer.
Zytiga therapy was well tolerated by both groups. Among the men in group B (who received 24 weeks of Zytiga therapy), 34 percent experienced complete elimination of nearly complete elimination of their cancer prior to surgery. In group A, where the men received Zytiga therapy for half of the treatment period, 15 percent of men experienced complete or nearly complete elimination of their cancer.
These are significant results in a population of patients with a typically poor prognosis. The researchers concluded that the combination therapy could have the potential to improve outcomes for men with LHRPC. Further research is warranted to confirm these benefits.
Taplin ME, Montgomery RB, Logothetis C, et al. Effect of neoadjuvant abiraterone acetate (AA) plus leuprolide acetate (LHRHa) on PSA, pathological complete response (pCR), and near pCR in localized high-risk prostate cancer (LHRPC): Results of a randomized phase II study. Presented at the 2012 annual meeting of the American Society of Clinical Oncology, June 1-5, 2012, Chicago, IL. Abstract 4521.
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