That being the case, you'd think that a noninvasive, easy-to-administer screening test that can detect the presence of nearly all types of cancer months before conventional diagnostic techniques can would be a medical breakthrough that would be trumpeted from the rooftops.
So why isn't the name of Dr. Samuel Bogoch--who has created such a test--not splashed over every newspaper and TV screen in America?
Well, there's a hitch. While the test appears to be much more sensitive than any other cancer screening test available, it lacks specificity. The test can tell a doctor whether cancer might be present, but it can't tell the doctor where the cancer is in the body, and therein lies the problem.
Malignin is a polypeptide. It's found in most cancer cells. It is also what is called an "antigen." The AMAS test measures how much of a substance called an antibody is in the blood--which a cancer patient's immune system produces in response to this antigen.
The test has been studied in numerous clinical trials, and is licensed for commercial use by Oncolab, in Boston. In testing, the AMAS generally has an accuracy rate in the 90% range. Compared to many other cancer marker tests, that accuracy rate would put the AMAS far ahead of just about every other cancer screening test available. And yet, the test's limitation are obvious. It doesn't do an individual any good to know he or she may have cancer if doctors can't find out where the tumor is and treat it. Still, it represents a promising potential diagnostic tool if further testing bears out the accuracy rate. It also represents an avenue for immunological treatments for cancer, and Bogoch's lab--among others--is currently doing animal studies on the antimalignin antibody's ability to attack cancer cells.
Although the idea of using the body's own immune system to launch an attack on cancer cells is not new, it is only recently that widespread research efforts in immunological approaches to cancer have been undertaken. In fact, several vaccines against specific types of cancer are currently being tested in rigorous FDA drug trials. A vaccine against melanoma, an especially deadly form of skin cancer, is reported to be showing promise in current trials.
"In an ironic way, AIDS helped to change a lot of people minds about cancer vaccines," says Bogoch. "In many AIDS patients, we saw that there's an increased frequency of cancer of certain types. That increase was traced to a failure of the immune system and provided the first indirect evidence of human immune response to cancer."
Because Bogoch's cancer screen is such a test, the FDA says that it has not reviewed or approved it, but neither has it disapproved it. But a source inside the FDA told CBSHealthWatch by Medscape that some experts within the organization are skeptical of Bogoch's claims. Despite official fence-straddling from the FDA, some cancer experts have been taking closer looks at the test.
In a statement that emphasizes the point that the AMAS is sensitive but not specific, Dr. Avrum Bluming says, "Using this test as a general screening for cancer would be a nightmare because of the problem of not being able to find and biopsy the cancer." Bluming, a clinical professor of medicine at the University of Southern California who has used the AMAS test on more than 50 patients, in part to see whether it has merit, adds, "But despite that, I think there is some very suggestive evidence about the test.
"Dr. Bogoch has run a study of more than 8,000 patients with the test, and the results he's reported are much better than any other cancer marker test we've got. However, my own experience with the test is not quite as good as the reported results."
Bluming says he gets the best results from the test when he uses it to check for tumor malignancy in patients who have confirmed cases of cancer. Originally, he tried to use the test to help him decide whether "second look" operations on women with advanced ovarian cancer--after surgery and chemotherapy--were justified to check for and remove any residual cancer.
"But in cases of advanced cancer, the test is not as accurate, because the immune system has been overwhelmed and the readings become inaccurate," says Bluming. "In some cases the test would be negative, but we'd find more cancer on a second surgery. In other cases, the test would be positive, and we wouldn't see anything on a second look."
Despite his mixed results with the test, Bluming says the test has a real role in cancer therapy and that its role may grow if more testing bears out Bogoch's findings.
"For now, the test is most useful when you have a potential problem and you're not sure what to do with it," he says. "You have a questionable X-ray or CAT scan of the chest, that kind of situation. You know something is there, and you know where it is, and the test could be an additional measure to better gauge how aggressively to treat a cancer. But if widespread testing of this test conforms to Bogoch's findings, then this test could be of enormous significance."
What Doctors Who Use it Say"I'm shocked that this very innovative tool is not being used more widely," says Dr. Stephen B. Edelson, who frequently uses the AMAS in his clinical molecular medicine practice at the Edelson Center for Environmental and Preventative Medicine in Atlanta. "I've been using the test for 7 years, and I've been very pleased with it."
But there are downsides to the test, Edelson concedes. When the test gets a positive result for cancer, the test is repeated. If the AMAS level is still high on repeated tests, the patient may feel obligated to go through expensive rounds of conventional testing that may not be able to detect cancer at its very early stages.
"It can be like looking for a needle in a haystack," says Edelson, who prefers to use the test to monitor patients with high risk for cancer and to monitor the progress of patient's after cancer treatment, especially surgery. "I hear surgeons say to patients, 'We got all your cancer,' when you know damn well the surgeon has no way of knowing what's going on at the cellular level. But the AMAS test can tell you whether they really got it all, and the fact that more oncologists don't use this test just blows my mind."
Dr. Carol Ann Ryser, who uses the AMAS test in her preventive medicine practice at the Health Centers in Kansas City, Missouri, echoes Edelson's impression of the test.
"I always research a test before I use it in my practice," says Ryser. "When I started looking at AMAS about 4 years ago, I looked at all the clinical studies, many of which were from reputable university clinical trials."
Ryser uses the test to create a baseline profile of patients who have a family history of cancer and for patients who are recovering from cancer treatment. For her patients over 50, she recommends the test as part of routine screening every 12-16 months.
"The problem with the test is that it doesn't tell you exactly where the cancer is in the body," says Ryser. "With about 80% to 90% of my patients who are positive for cancer on repeated tests, I can use other tests to figure out where the problem is exactly. But you need to do a lot of detective work, and that testing can be expensive, and justifying that expense to a managed-care company can be a problem. Doctors get penalized for ordering too many tests."
© 2000 by Medscape Inc. All rights reserved.
John Casey is a staff member of CBSHealthWatch by Medscape.