"A noninvasive scan might someday help doctors track the progress of prostate cancer and help guide treatment researchers report.  The imaging tool known as a prostate cancerspecific radiotracer has so far only been tested successfully in mice. But a team from Memorial SloanKettering Cancer Center in New York City said the technology could help identify cases where prostate cancer has spread to the bone.  Radiotracers work by injecting a small amount of a compound tagged with a radionuclide into patients. Using positron emission tomography  also known as a PET scan  doctors are then able to better visualize tumors and tumor spread.  In studies involving mice with prostate cancer the researchers had the radiotracer hone in on prostatespecific antigen PSA the same prostate cancer marker used in the PSA test. They found that the PSA gravitated to tissues containing prostate cancer that had already grown resistant to standard hormonebased therapies.  The study also revealed the radiotracer could help identify cases where prostate cancer had spread to the bone. The researchers pointed out traditional bone scans are unable to differentiate between malignant and nonmalignant lesions.  The findings were to be presented Saturday at the American Association for Cancer Research annual meeting in Chicago and are also being published in Cancer Discovery.  If used on people the researchers claimed that the radiotracer might someday help doctors personalize treatment strategies for prostate cancer and better manage the disease.  The ultimate goal is to be able to predict the response of patients to new and existing therapies at an early stage thereby personalizing their treatment and improving outcomes Michael J. Evans research fellow in the Human Oncology and Pathogenesis Program at Memorial SloanKettering Cancer Center explained in meeting news release.  Encouraged by their findings the studys authors said they hope to begin a human trial next year.  Two prostate cancer experts said the tool if borne out in patients could prove very useful.  Dr. Michael Schwartz is director of laparoscopy and minimally invasive surgery at North ShoreLIJ Health System in Lake Success N.Y. He noted that as of now doctors typically rely on results of the PSA blood test andor standard diagnostic scans to help guide treatment decisions.  Both methods have their limits and while this study is very preliminary if this radiotracer technology can prove to detect very early recurrence or metastasis in human patients it could become extremely useful in either the pre or posttreatment setting in selecting a treatment algorithm Schwartz said. It also may help reduce the need for biopsy of possible metastatic lesions.  Dr. Erik Goluboff an attending urologist at Beth Israel Medical Center New York City agreed that this is an exciting study using a novel radiotracer to detect PSAexpressing tissues throughout the body.  He believes that the new tools greatest strength would be in monitoring changes in PSA expression in tissues as a result of various treatments. If a treatment showed a marked change it could continue to be used in that patient hence personalized medicine. If a specific change did not occur that treatment could be abandoned and another tried instead. Since these changes could not be detected based on a PSA blood test alone this new test would be very helpful in determining early on which therapy to choose in a given patient.  However Goluboff also noted that research from animalbased studies does not always pan out in humans and further larger studies are of course required to confirm these findings.  More information  The U.S. National Cancer Institute provides more information on prostate cancer.  SOURCE Michael J. Schwartz M.D. director laparoscopy and minimally invasive surgery Arthur Smith Institute for Urology North ShoreLIJ Health System Lake Success N.Y. Erik T. Goluboff M.D. attending urologist Urologic Oncology Beth Israel Medical Center New York City The American Association for Cancer Research news release March"