Scientists in the Division of Urology and Urologic Oncology have found a potential new prostate cancer screening method, according to findings published in the December 2008 issue of Clinical Chemistry. The diagnostic test could one day dramatically reduce the number of unnecessary prostate biopsies.
The research shows the new noninvasive test, when added to modern standard screening tests, could improve the accuracy of diagnosis.
Physicians currently screen for prostate cancer by using a digital rectal examination to feel for tumors and by measuring levels of prostate specific antigen, or PSA, in a man’s blood. If these noninvasive tests hint at cancer’s presence, a physician then takes a biopsy to confirm the diagnosis.
|Steven Smith, left, discusses study data with Laura Crocitto. (Photo by Darrin S. Joy)|
In a prostate biopsy, doctors surgically remove a sample of prostate tissue from the area of a suspected tumor and examine it for cancer cells. Pathologists then examine the sampled cells and assign them a Gleason score.
Gleason scores are a measure of the aggressiveness of prostate tumors. The higher the score, the more aggressive the cancer.
Biopsies are needed to confirm cancer, but today, more than 60 percent of biopsies suggested by screenings ultimately turn up negative. This means about two-thirds of these screenings give false positive results, and the ensuing biopsies to confirm the diagnoses are unnecessary.
The new test provides a noninvasive means to predict the outcome of the biopsy before the biopsy results are available. City of Hope researchers believe their work will sharpen screening accuracy.
“Our combined test provides a considerable improvement over current noninvasive tests,” said Steven Smith, Ph.D., professor of molecular science and principal investigator on the National Cancer Institute-funded project. “The clinical value lies in the possibility that unnecessary and sometimes painful biopsies could be avoided.”
The new test involves massaging the prostate gland to push fluid from it, then testing the fluid for DNA biomarkers that point to the presence of cancer. DNA biomarkers are altered forms of DNA that appear in cancer but not in normal tissue.
For their study, the researchers collected prostatic fluid from about 75 patients who had already had noninvasive screenings followed up with biopsies. Without knowing biopsy results, they compared three different biomarkers in each patient’s prostatic fluid and tried to predict whether or not the biopsy would show that cancer was present.
They found that all three biomarkers could predict the outcome of the biopsy with some level of accuracy, but one test clearly stood out as the best: a biomarker called TMPRSS2:ERG, used in combination with the digital rectal exam and PSA results.
The results also suggested that this combination most accurately predicted the Gleason score for those patients who did have cancer.
|Timothy Wilson (Photo by Markie Ramirez)|
“By adding this third component to the current prostate cancer screening standards, we could potentially save the health-care system a great deal of money, not to mention the pain, inconvenience and worry the men go through,” said Timothy Wilson, M.D., Pauline and Martin Collins Family Chair in Urology and chief of the division.
Wilson and Smith, along with Laura Crocitto, M.D., assistant professor of surgery, Mark Kawachi, M.D., associate professor of surgery, Kevin Chan, M.D., clinical assistant professor of surgery, and Jeffrey Yoshida, M.D., former City of Hope clinical fellow, all collaborated on the project.
According to Wilson, the collaboration exemplifies what clinical researchers and laboratory scientists can achieve when working together closely. “The urology division has been building a strong reputation in patient care through our efforts in minimally invasive surgery. Our efforts in noninvasive diagnosis are strengthening our reputation in research,” he said.
The work is so promising that the American Urology Association invited the team to present its work at the podium session of the association’s annual meeting last spring. The City of Hope team is collaborating with researchers at Fred Hutchinson Cancer Research Center on the project.