CHICAGO, Dec. 4 (UPI) -- A specially modified type of magnetic resonance imaging is as effective as biopsy for identifying aggressive prostate tumors with the additional advantage of being able to provide "a roadmap for treatment," researchers reported Wednesday.
In the past, cancer specialists had to rely on surgical biopsy to determine tumor grade, which is a key factor in predicting survival, but the new technology can establish a "metabolic signature for the tumor" that is as accurate as standard biopsy, said Dr. Hedvig Hricak, chair of the department of radiology at Memorial Sloan-Kettering Cancer Center in New York City.
The technology is called photon magnetic resonance spectroscopic imaging or MRSI and it is so new only two centers -- Memorial Sloan-Kettering and the University of California, San Francisco -- have it, Hricak said, adding she expects it be available in 10 more centers by late 2003.
She predicted the new technology will not "completely replace traditional biopsy, but will be used along with biopsy and PSA to better guide therapy." PSA -- for prostate specific antigen -- is the blood test used to screen for prostate cancer. PSA levels increase when the prostate is enlarged either because of benign growth or cancer.
MRSI works by imaging two substances found in the prostate: choline and citrate. As tumors become more aggressive, choline levels increase and citrate disappears, Hricak said. She and her colleagues discovered this correlation when they compared MRSI images taken before surgery in 127 patients.
The patients all had biopsy-confirmed prostate cancer and when the prostate glands were surgically removed, Hricak and her team were able to compare their existing MRSI images to the pathology reports on excised glands.
Pathologists grade tumors using a system called Gleason scores that related to the composition and growth potential of the tumor. The higher the Gleason grade -- 10 is the highest possible score -- the more aggressive the tumor. Hricak said MRSI was able to identify 72 percent of the most aggressive tumors accurately -- those with Gleason scores of 7.5 or higher.
"That may not sound like much but it is actually more accurate than biopsy," Hricak said. She added MRSI has a slight edge over biopsy because sometimes "the biopsy misses the tumor because the cancer is located in a different part of the gland." The scan images the entire prostate and highlights the tumor, so "missing" is not a problem.
Dr. Fergus Coakley, associate professor and chief of abdominal imaging at UCSF was not involved in the MSK study but said the work there confirms earlier MRSI studies at UCSF.
"Here the typical scenario is that the patient has an elevated PSA and positive biopsy but the treating physicians are unsure about treatment," Coakley said. "We use MRSI to stage the cancer and direct treatment."
