A new study published in the international journal The Lancet suggests researchers are able to detect deadly ovarian cancer with a simple blood test. The test offers hope of catching the disease when it is most curable.
By the time most women with ovarian cancer have symptoms - including abdominal bloating and vague stomach and back pains - cancer cells have usually spread from the almond-shaped ovaries to other nearby, vital organs, and the disease is at an advanced stage.
Ovarian cancer is also difficult to diagnose in the laboratory. A protein called CA-125 is sometimes elevated in women with ovarian cancer. But a blood test to detect CA-125 levels fails to do so in half of all early stage cancers.
Emanuel Petricoin is a senior investigator at the U.S. Food and Drug Administration. Because efforts to identify specific cancer markers such as CA-125 have been disappointing, Dr. Petricoin says researchers decided to try an entirely different approach involving protein patterns in the blood.
"This concept of patterns is new, and we needed to prove that hypothesis and we decided to use it in a disease that really needs a lot of work, and that is detecting ovarian cancer. ... Because simply having a bio-marker that detects ovarian cancer early makes a huge impact on that disease because if you catch it early enough, it's almost curable," said Dr. Petricoin.
The FDA joined forces with the National Cancer Institute to create the screening test for ovarian cancer. NCI head pathologist Vance Liotta explained the test looks at the pattern of proteins in the fluid portion of blood and their relationship to one another.
"The hypothesis that Dr. Petricoin and I had was that changes in the patterns in the proteins in the fluid of the blood would reflect underlying disease going on in internal body organs, because the blood circulates through all the organs and around and around many times a minute. And so if there are proteins that are shed into the blood from the diseased tissue, we might be able to pick it up," he explained.
But literally millions of proteins are shed into the blood of different lengths and widths. So researchers needed a mass spectroscopy computer program to help them sort out the cancerous fluid samples from the non-cancerous ones.
Scientists had the computer assess 50 samples taken from women with known ovarian cancer. And it assessed the protein patterns in blood samples from women who were at high risk for ovarian cancer, but cancer-free.
Once investigators had the information for comparison purposes, they did their experiment, which involved 166 participants, some of who had ovarian cancer. But the FDA's Emanuel Petricoin sayid researchers were kept in the dark about which participants had cancer and which didn't until the end of the study.
"And then we unblinded the set, and we asked 'How well did we do?' And it was able to, in the 50 patients that we had that had cancer, it was able to distinguish all of them correctly, including all 18 Early Stage I cancers ... and we had 66 women who were healthy or had benign gynecologic malignancies or just inflammatory diseases," said Dr. Petricoin.
Among this last group, the protein test incorrectly diagnosed three healthy women with ovarian cancer.
Scientists are likely to speed up research on the protein test, which they think could be used to detect other cancers.