Ovarian cancer kills two-thirds of the women who get it, largely because it can develop undetected for too long.
Nine in 10 women who have ovarian cancer that has not spread survive at least five years. But most cases are diagnosed in advanced stages, making diagnostic screenings especially important.
“At the moment all our attempts are to try and pick up the disease earlier,” said Usha Menon, Ph.D., the lead investigator in the University College of London study.
A study just published in the Journal of Clinical Oncology raises hope that a simple blood test could catch cancers early enough to spare some women’s lives. The screening method uses an existing test but introduces a different way to interpret results.
The best current test for ovarian cancer is a blood test that measures cancer antigen 125 (CA-125). Women with higher levels of CA-125 are referred for further screening. But the test catches just 40 percent of cancers. It also has high false-positive rates. Due to its limitations, it is not recommended for most women.
The new study proposes a sharper way to read the CA-125 numbers based on a woman’s age and how much the antigen’s levels increase over time. Rather than flag only women whose levels exceed the standard threshold of 35, it would flag women whose levels suddenly increase.
“What this is doing is looking at each woman’s individual level. Mine might be 8, so if it goes to 15, it’s still not over the cutoff, but our algorithm would pick it up because it’s not usual for me,” Menon said.
The blood test was used to classify women’s risk of ovarian cancer as normal, intermediate, or elevated. Women who were at elevated risk received an ultrasound scan to look for cancer. If the scan was negative, they underwent a second blood test in six weeks.
Women who were at intermediate risk returned for a follow-up blood test in three months. Women who were found at normal risk were told to come back in a year.
Over 10 years, this approach turned up twice as many cancers as the current way of reading CA-125 screens. The study detected cancer in 86 percent of women with invasive epithelial ovarian cancer. The conventional method would have identified fewer than half of these cases.
Will the New Approach Save Lives?
It remains to be seen whether the earlier detection will translate into better survival rates. A 2011 American study showed that using CA-125 cutoff testing did not change mortality rates.
New cancer drugs, including bevacizumab (Avastin), that have proven effective against other forms of cancer have also failed to extend average survival times for women with ovarian cancer.
“The question is whether by picking up these women early we were able to save their lives,” Menon said.
The CA-125 algorithm approach will also need to show that its rates of false positives are worth the risk.
More than 600 women underwent surgery in the 10-year program after they were categorized as high-risk and had irregular ultrasound scans. But only 1 in 5 actually had cancer.
“The question is, ‘Does this translate immediately into having an ovarian cancer screening program?’ The truth is no because this is a step toward a final answer,” Menon said.