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Short CAG Repeat in Androgen Receptor Respond Better to Androgen Ablation
NA
volume 3 | issue 11
november 2004Pages: 1040-1041
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Physician-scientists at the University of Miami Sylvester Comprehensive Cancer Center have identified a way to predict which prostate cancer patients may benefit most from continued androgen ablation therapy to block hormones. The research was presented at the 46th annual meeting of the American Society for Therapeutic Radiology and Oncology in Atlanta, Georgia, October 3 -7.
"We found a subgroup of patients that benefited from androgen ablation therapy, regardless of other known prognostic factors in prostate cancer," said May Abdel-Wahab, M.D., associate professor of Clinical Radiation Oncology at the UM School of Medicine and a member of the Genitourinary Cancer Site Disease Group at UM/Sylvester.
The subgroup of patients in the study have what are called short CAG repeats. CAG stands for cytosine, adenosine and guanosine, three nucleotides which are the building blocks of DNA. These three nucleotides appear repeatedly on androgen receptor genes, with longer repeats in some people. CAG repeats number anywhere from 14 to 32 in the androgen receptors of healthy people. "Patients with lower CAG repeats who received hormone ablation and radiation on the study had improved local disease control over those treated with radiation alone, regardless of their Gleason score, stage or age," said Abdel-Wahab, the principal investigator of the study.
UM researchers worked with the Radiation Therapy Oncology Group, a top national cancer research collaborative, to acquire prostate tumor samples from patients who had been treated on the RTOG 86-10 study. They isolated androgen receptor lengths using polymerase chain reaction (PCR), a quick way to analyze DNA, and measured the percentage of positive androgen receptors by flow cytometry (analyzing the content of samples with a laser).
"We found that people with short CAG repeats (fewer than 19) that were treated with hormone ablation and radiation actually did better in terms of local tumor growth control," said Abdel-Wahab. "However it didn't affect overall survival in these patients." In this study, the hormone blocking therapy was temporary and was given for only 4 months. "If you prevent androgens for a long time you might be able to slow down the progression of disease in these patients, or maintain a longer remission."
"If these patients had gotten long-term androgen ablation the favorable results may have been preserved because they're the ones who are far more likely to have their cancer stimulated by the presence of androgens," said Abdel-Wahab. "You could possibly choose the people who might benefit from long-term hormonal therapy, and that's why it's exciting."
Prostate cancer is the most common malignancy in the United States, with about 230,000 new cases diagnosed every year. Nearly 30,000 men will die from prostate cancer this year. In Florida alone, more than 17,000 new cases will be diagnosed and more than 2,200 people will die.
If you want to learn more about this study, please call (305) 243-1000.
UM/Sylvester was founded in 1992 to provide comprehensive cancer services and today serves as the hub for cancer-related research, diagnosis, and treatment at the University of Miami School of Medicine. UM/Sylvester handles more than 1,100 inpatient admissions annually, performs 2,800 surgical procedures, and treats 2,900 new cancer patients. All UM/Sylvester physicians are on the faculty of the University of Miami School of Medicine, South Florida's only academic medical center. In addition, UM/Sylvester physicians and scientists are engaged in more than 150 clinical trials and receive more than $30 million annually in research grants. UM/Sylvester at Deerfield Beach recently opened to better meet the needs of residents of Broward and Palm Beach Counties. This 10,000 square-foot facility at I-95 and S.W. 10th Street offers appointments with physicians from six cancer specialties, complementary therapies from the Courtelis Center, and education and outreach events. http://www.sylvester.org.
We now provide open access to journal articles published online for one year or more. This article may be downloaded at the following link:
Download PDFIf the document does not open, please right-click on the link (control-click on a Macintosh) and select the option to save the file to disk.