SALT LAKE CITY, UTAH--The largest known biomarker study for prostate cancer patients treated with radiation therapy shows that the presence Ki-67 may be a significant predictor of patient outcome for men with prostate cancer treated with both radiation and hormones. The study was sponsored by the Radiation Therapy Oncology Group and was presented today by Alan Pollack, M.D., Ph.D., chairman of radiation oncology at Fox Chase Cancer Center, at the 45th annual meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO) in Salt Lake City, Utah.
The Ki-67 biomarker is a proliferation antigen that is detected by a process called immunohistochemical staining. When a tumor cell tests positive for Ki-67, the tumor is actively growing.
Prostate cancers typically have very low percentages of growing cells and they grow slowly. Pollack and others have previously shown in smaller studies that the greater the proportion of prostate tumor cells with Ki-67, the more aggressive the cancer. Prior studies involved small patient numbers and did not definitively establish the usefulness of the Ki-67 biomarker.
"Our study conclusively shows that Ki-67 was the most significant determinant of distant metastasis and death in prostate cancer patients," explained Pollack. "The relationship of Ki-67 to patient outcome is a continuous function, wherein the higher the percent of Ki-67, the greater the risk of an adverse result. In addition, Ki-67, along with PSA, Gleason score and stage, appears to be valuable in determining whether high-risk patients may be spared long-term androgen deprivation."
Pollack says that a consistent threshold for the application of Ki-67 on a routine basis has not been previously established. In this study, when greater than 7.1% of the tumor cells stained for Ki-67, there was a significantly increased risk of distant metastasis and death due to prostate cancer.
Furthermore, Pollack adds, Ki-67 should be very usefPage: 1 2 Related biology news :1
Contact: Karen Carter Mallet
Fox Chase Cancer Center
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