‘Marker’ Study May Advance Detection of Cancer
Do you have cancer?
Some day, doctors may be able to use a simple, relatively painless blood test to find out.
And that day could come much sooner if researchers investigating such a test can find enough Orange County cancer patients willing to participate in their study.
According to preliminary findings from a coded, blind study, the test can detect cancer of various types with better than 95% accuracy by looking for the presence of a tumor marker known as the ring-shaped particle. The test also correctly identified patients without cancer better than 85% of the time, and as high as 91.3% of cases when patients with a specific non-cancerous disease, systemic lupus erythematosus, were excluded. In further testing on perfectly normal subjects, the tests were correctly negative in more than 97% of cases.
Dr. Glen Justice of Pacific Coast Hematology/Oncology Medical Group at the Fountain Valley Regional Hospital and Medical Center and the Pacific Coast Comprehensive Cancer Center in Tustin, who presented those findings last month to a meeting of the American Society of Clinical Oncology in Houston, says more tests are necessary to confirm accuracy and practical applications.
Although the statistical chance that the original research was inaccurate is somewhere around one in a million, the doctors must confirm their findings on a larger sampling before the test can be used in actual medical practice. “We need rock-hard large numbers that are irrefutable,” Justice says.
The doctors are looking for 300 volunteers, all of whom either currently have or previously had breast cancer. They are also testing women without cancer for comparison. Each test subject will have a small sample of blood drawn for the study, and there is no charge. The researchers hope to find enough participants to complete their study by the end of June.
The original study tested the blood of 135 patients, 73 of whom were known to have cancer, 22 different types in all. Samples were coded so that those performing the actual test did not know which were from cancer patients and which were not. The test correctly identified 71 of the 73 cancer patients, and came back negative for 53 of the 62 non-cancer patients. Two of those thought to be false positives were later found to be accurate. Most of the other false positives were patients with systemic lupus erythematosus, an autoimmune disorder.
The ring-shaped particle, a macromolecular complex made of protein, ribonucleic and deoxyribonucleic acids (genetic material better known as RNA and DNA), was detected by researchers in cultures of malignant cells as early as 1973, and subsequent studies have shown that its presence often correlated with the presence of cancer. But until now, there has been no easy way of testing for it.
Then a Mission Viejo Company, AMDL, developed a detection probe for identifying the ring-shaped particle.
Justice, who has done research with several universities and with AMDL on early cancer markers, admits he was somewhat skeptical when the company asked him to experiment with the test, but now the results have him excited.
Researchers have been aware of the presence of biological markers for various types of cancer for several decades, but except in very specific types of tumors, those markers haven’t been very consistent or useful. For example, a marker known as CA-125 has been associated with ovarian cancer, but at best it has been found in only about 60% to 70% of cases.
Unlike other markers, the ring-shaped particle appears to be a universal marker for cancer, Justice says.
“We used to think that cancer was really more than 300 different diseases,” he says. “But now we’re moving away from that. Current research is showing that certain genes, which are known as oncogenes, seem to play a major role, and the combined presence of these cancer-causing genes and another factor, such as radiation or a virus, allows cancer to develop.”
The ring-shaped particle also seems to increase as tumors develop, and it disappears when the cancer is removed or destroyed.
In fact, two former cancer patients whose blood was tested for the preliminary study were originally thought to be false positives, because the ring-shaped particle was found in their blood even though they were free of disease. But both subsequently had recurrences, one with adrenal cell cancer and another with colon cancer. After surgery to remove the tumors, their blood tests reverted to normal.
Both patients had been in for regular checkups, but normal procedures had not detected their new tumors.
Justice and the other researchers are concentrating specifically on breast cancer for this study, and he says a blood test could be particularly useful for those patients.
“Breast cancer is epidemic in this country right now,” he says. “We’re diagnosing 180,000 women a year, and we’re losing 75,000 women a year to the disease. A woman now has a 1 in 9 chance of being diagnosed sometime during her life.”
After their tumors are removed either through mastectomy or lumpectomy, some breast cancer patients will suffer recurrences of the disease. Justice hopes that a tumor marker test could help doctors determine which patients need further treatment, such as chemotherapy, and which do not, as well as judging the quality of the patient’s response to therapy.
Eventually, a test such as this one could also be used to help doctors locate tiny tumors that aren’t big enough to be detected by other methods, such as CAT or magnetic resonance scans. Since tumor markers are secreted by the tumor itself, ultimately it may be possible to attach a dye to antibodies for the marker that could show up on certain kinds of scans, Justice speculates.
“Having a simple means of detecting cancer is something doctors have always dreamed of,” Justice says. “It can make a tremendous difference both in early detection, which makes the disease much easier to treat and the chances of cure and survival greater. It hopefully will also be very effective in detecting early relapse. We always hope that we’ve killed every last tumor cell, but we’ve never had any way of knowing for sure.”
To participate in the study, call Pacific Coast Hematology/Oncology at 751-2600.
