A novel agent, ABT-627, appears to delay the progression of cancer in patients with hormone-refractory prostate cancer with few side effects, according to recent reports presented at the 37th Annual Meeting of the American Society of Clinical Oncology.
The prostate is a male sex gland located between the scrotum and rectum. Standard therapy for prostate cancer may consist of watchful waiting, radiation therapy, chemotherapy, surgery, cryotherapy, and/or hormonal therapy alone or in combination. Once prostate cancer reaches an advanced stage, it often spreads to the patient’s bones, which causes debilitating pain and bone fractures. Typically, radiation therapy is used to treat the bone cancer, but is associated with significant side effects. When patients have reached this stage of disease, they have often exhausted most of their treatment options and are left with few choices.
ABT-627 is a novel agent still in clinical trials that appears to delay the progression of spread of prostate cancer. ABT-627 works by blocking endothelin, a protein known for its vasoconstrictive properties. Endothelin is produced in excess amounts by prostate cancer cells and is speculated to act as a cellular growth enhancer and promoter of cancer spread to the bone. However, the exact mechanism by which endothelin contributes to the progression of prostate cancer is unknown.
One clinical trial evaluating ABT-627 involved 244 patients with hormone-refractory prostate cancer whose disease was progressing. One group of patients received ABT-627 and the other group received a placebo (inactive substitute). Those taking ABT-627 had the progression of their disease delayed by nearly 70 days compared to those taking a placebo. In addition, the group of patients who received ABT-627 took twice as long for a rise in their prostate specific antigen (PSA) levels (a protein secreted by prostate cancer cells used as an indicator for cancer progression). Few patients experienced mild side effects.
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A second clinical trial evaluated ABT-627 and its effects on cancer progression, specifically to the bone in hormone-refractory prostate cancer patients. During this trial, patients who received ABT-627 maintained stable levels of blood “markers”, which are used as an indicator of cancer spread to the bones. Conversely, patients receiving a placebo demonstrated a continued elevation in these markers, indicating a continual progression of cancer spread to the bones.
A third study involving ABT-627 evaluated the effects of this agent on a patient’s quality of life. Patients receiving ABT-627 reported a 30% improvement in quality of life issues over patients who received a placebo.
The results from these combined studies indicate that ABT-627 may help delay the progression of prostate cancer and improve quality of life for patients with hormone-refractory disease. Researchers report that ABT-627 may be used for patients who have no treatment options left or for patients who choose to receive less toxic therapies before resorting to chemotherapy or radiation and their associated side effects. Patients with prostate cancer may wish to speak with their physician about the risks and benefits of participating in a clinical trial further evaluating ABT-627 or other promising therapies. Two sources of information regarding ongoing clinical trials include comprehensive, easy-to-use listing services provided by the National Cancer Institute (cancer.gov) and eCancerTrials.com. eCancerTrials.com also provides personalized clinical trial searches on behalf of patients. (Proceedings from the 37thAnnual Meeting of the American Society of Clinical Oncologists, abstract #12, 694, 1567, San Francisco, CA, May, 2001)
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