Ki-67 Biomarker Is a Strong Predictor of Outcome For Prostate Cancer Patients Treated with Androgen Deprivation plus Radiotherapy
SALT LAKE CITY, UTAH (October 21, 2003) — 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, MD, PhD, 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 useful in stratifying patients in future clinical trials.
Other authors in the study include Michelle DeSilvio, American College Of Radiology, Philadelphia, Pa.; Li-Yan Khor, Fox Chase Cancer Center, Philadelphia, Pa.; Rile Li, Baylor School of Medicine, Houston, Tex.; Tahseen Al-Saleem, Fox Chase Cancer Center; M. Elizabeth Hammond, University of Utah School of Medicine, Salt Lake City; Varagur Venkatesan, Medical College of Wisconsin, Milwaukee; Roger Byhardt, University of California San Francisco, Calif.; Gerald E. Hanks, retired from Fox Chase Cancer Center; Mack Roach, University of Western Ontario, London, Ontario; William Shipley, Massachusetts General Hospital, Boston; and Howard Sandler, University of Michigan Medical Center, Ann Arbor.
Fox Chase Cancer Center, part of Temple University Health System, is one of the leading cancer research and treatment centers in the United States. Founded in 1904 in Philadelphia as one of the nation’s first cancer hospitals, Fox Chase also was among the first institutions to receive the National Cancer Institute’s prestigious comprehensive cancer center designation in 1974. Fox Chase researchers have won the highest awards in their fields, including two Nobel Prizes. Fox Chase physicians are routinely recognized in national rankings, and the Center’s nursing program has achieved Magnet status for excellence three consecutive times. Fox Chase conducts a broad array of nationally competitive basic, translational, and clinical research and oversees programs in cancer prevention, detection, survivorship, and community outreach. For more information, call 1-888-FOX-CHASE (1-888-369-2427).