A researcher works near a blood test machine recently developed that is so sensitive it can spot a single cancer cell lurking among a billion healthy ones, Jan. 3, 2011.
A researcher works near a blood test machine recently developed that is so sensitive it can spot a single cancer cell lurking among a billion healthy ones, Jan. 3, 2011.
Researchers are exploring a new strategy that would allow a blood test, long used to detect ovarian cancer in women suspected of having the disease, to function as a screening tool for the lethal illness in healthy women.

Ovarian cancer is responsible for nearly two percent of all cancers diagnosed globally each year, according to the World Cancer Research Fund International. The disease is highly lethal because it often causes no specific symptoms in its early stages, and by the time a woman goes to the doctor complaining of abdominal bloating and pain, it's often too late for effective treatment.

Karen Lu, chair of the Department of Gynecologic Oncology at the University of Texas M.D. Anderson Cancer Center in Houston, said, “We know that over 75 percent of women with ovarian cancer present at late stages when our chances for a sustained cure can be quite low. And we know that if we catch it very early we know that our chances for cure, for long-term cure, can be as high as 90 percent.”

The chance to catch the cancer early could come from new thinking about a 20-year-old blood test. Doctors use the test, which checks for levels of a protein called CA-125, to confirm a diagnosis of ovarian cancer or to monitor the progress of women who are being treated.

Lu and her colleagues investigated the possibility of using CA-125 levels to screen older, post-menopausal women for the cancer.  

They were involved in an 11-year study of about 4,000 healthy women across the United States. The participants, ages 50 to 74 with no family history of breast or ovarian cancer, received a CA-125 blood test at the beginning of the study and were divided into three risk groups. The women were re-tested on a regular schedule for more than a decade.

Lu says those whose CA-125 scores were low and remained low came back annually to be re-tested. Women with an intermediate score on the biomarker test at any point were brought back three months later for a follow-up test. Women whose CA-125 levels were high on repeat testing were sent to a cancer specialist for an ultrasound exam. Eighty-five women were referred to an oncologist based on that exam. Surgery was recommended for 10 of the women, four of whom had early-stage invasive ovarian cancer. Among the remaining women, one had endometrial cancer, three had benign tumors and two had suspicious cellular changes.

The method or algorithm for placing women in the three risk groups, according to Lu, turned out to be almost 100 percent effective in detecting invasive ovarian cancer with the CA-125 test.

“When we see a rise, when we see a doubling from a low value of eight to 16, the algorithm in our case triggered the ultrasound which ultimately picked up the early stage cancer,” said Lu.

British researchers have completed a study of 200,000 healthy women to see whether their risk of death from ovarian cancer was reduced by yearly screenings.

Depending upon the results, Lu said the test also could be recommended for healthy women.

The results of the study by Karen Lu and colleagues are published in the journal Cancer.