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WEDNESDAY, June 18, 2003 (HealthDayNews) -- A new method for determining whether prostate cancer has spread to the lymph nodes is being hailed as a breakthrough by many experts in the field.
The technique, which uses a high-contrast agent with high-resolution magnetic resonance imaging (MRI), appears able to detect even tiny metastases in the lymph glands of men who have already been diagnosed with the cancer.
The study, reported in the June 19 issue of the New England Journal of Medicine, used an iron oxide-containing contrast agent that is not yet approved by the U.S. Food and Drug Administration (FDA), but is currently being evaluated.
"This technology provides potentially a revolutionary, very exciting approach toward the detection of metastatic cancer. I imagine this technology is going to be applicable to a number of different kinds of cancer," says Dr. W. Marston Linehan, chief of urologic surgery at the National Cancer Institute.
"Anything that improves diagnosis and minimizes invasive procedures for established diagnoses in cancer or any other disease process is obviously a step forward," echoes Dr. Gilbert J. Wise, director of urology at Maimonides Medical Center in New York City.
Right now, finding out if cancer has spread to the lymph nodes is an imprecise endeavor. "It's very hard for us, even with our best imaging, to determine whether the nodes are affected or not," Linehan says. Technological advances have made the job easier, but it's still not foolproof. "It's a probability," Wise says. "It's looking at race horses."
And whether or not a cancer has spread to the lymph nodes is crucial information because it determines how treatment will proceed.
"There are three main ways that patients can be treated with prostate cancer. The patient can either go for surgery, radiation or hormonal therapy," explains study author Dr. Mukesh Harisinghani, a radiologist in the abdominal imaging division at Massachusetts General Hospital in Boston.
"When the disease is confined to the prostate gland, surgery is an option because you want to take the primary cancer out and prevent it from spreading. If the tumor has spread to the lymph nodes, that precludes going to surgery because it is assumed the cancer has already spread," he adds.
Despite many advances, more than 30,000 men died of prostate cancer every year. "We continue to see an alarmingly high mortality rate," confirms Dr. Daniel Shasha, co-director of genito-urinary oncology for Continuum Health Partners in New York City. "Why are all these patients failing while so few are presenting with radiographic metastases? One of the reasons is the nondiagnosis of microscopic metastatic cancer, and that's where this study becomes very, very important."
Harisinghani and his colleagues used the new MRI method to assess 334 lymph nodes that had been taken from 80 patients with prostate cancer. The first group of 40 patients was treated at Massachusetts General between 1999 and 2002; the second group of 40 patients was treated at the University Medical Center in Nijmegen, the Netherlands, between 1999 and 2001.
All the patients had a preliminary high-resolution abdominal MRI. They then received intravenous infusions of the high-contrast agent and, 24 hours later, another set of MRI studies.
Afterwards, the lymph nodes were also removed to compare the MRI results with a regular dissection. The new MRI technique correctly identified all patients with positive lymph nodes and had a much higher sensitivity on a patient-by-patient basis than conventional MRI (100 percent versus 45.4 percent).
In all, 272 of the nodes were benign. Metastases (cancer that had spread) was found in 63 modes (18.9 percent) from 33 patients (41 percent). Of these, 63 positive nodes, 45 (71.4 percent) were so small they would not have been picked up by current imaging techniques.
Traditional imaging techniques are primarily anatomic and look at different parts of the body, Harisinghani explains, adding, "This is one step beyond. You are trying to assess one attribute of lymph nodes and, based on that, make an assessment." That attribute is how the lymph nodes take up the high-contrast agent.
Theoretically, the procedure appears to be more effective, easier on the patient and even cheaper. "If anything, it's going to be a cost savings because now we will be able to accurately stage without having to undergo multiple steps," Harisinghani says.
However, there are practical problems with implementation. For one thing, it is not yet FDA-approved. But if and when that happens, there are not nearly enough MRI scanners to go around.
"In major hospitals there is always a struggle to meet the present demand of patients with MRI scans," Shasha says. "If this test is to be applied in a widespread fashion, the implications for the need for further MRI scanners being built are enormous."
Also, convincing insurance companies that there will be a cost savings will present another hurdle, Shasha points out. And larger studies are still needed to back up these findings.
Regardless, the new MRI technique appears to be "the right tool for the right job," Shasha says.
And there may be other applications. "It seems to me the same technology could be phenomenally valuable in evaluating responses to therapy," Linehan says. 'If you can have this precise look at the tumor with this noninvasive imaging, that would give you a much sharper tool for not only knowing which patients have a cancer which has spread outside the prostate, but which patients are responding to therapy."
"It's like a fighter pilot trying to land a plane: the more information you have the better off you are," Linehan says.