Ovarian cancer, detected early, is treatable - and a new blood test aims to do just that.
However, the United States' Food and Drug Administration (FDA) and some experts are not yet convinced by claims about the test, called OvaSure, reported The New York Times.
Developed at Yale, it has been offered since late June by LabCorp, one of America's largest clinical laboratory companies.
The need for such a test is immense. More than 90 per cent of women with ovarian cancer will live at least five years if it is detected at its earliest stage, when it is still confined to the ovaries, says the American Cancer Society.
Only about 20 per cent of cases are detected that early. When the cancer is detected after it has spread and is at its latest stages, only about 30 per cent of women survive five years.
Many experts do not seem elated about the new test, worrying it might do more harm by subjecting women to unnecessary surgery. The Society of Gynaecologic Oncologists said in its statement that it did not believe the test had been validated enough for routine use.
How OvaSure works
OvaSure measures the level of six proteins in blood, some produced by a tumour and some produced by the body in reaction to a tumour.
It then calculates the probability of a woman having ovarian cancer.
'OvaSure is very premature,' said DrAndrew Berchuck, director of gynaecologic oncology at Duke University and the society's immediate past president.
Others - noting that OvaSure did not go through an FDA review - urged greater regulation to assure the validity of a slew of sophisticated new diagnostic tests that are entering the market.
OvaSure costs about US$220 to US$240 (S$310 to S$340).
The FDA does not typically regulate tests developed and performed by a single laboratory, unlike test kits sold to laboratories, hospitals and doctors. All OvaSure blood samples are sent to LabCorp.
Now, the FDA has stepped in. It summoned LabCorp to discuss OvaSure, saying the data appear insufficient to back the company's claims about the test.
The agency's Aug 7 letter to LabCorp described the test as a 'high-risk' one 'that has not received adequate clinical validation and may harm the public health'.
A spokesman for LabCorp, which is short for Laboratory Corporation of America Holdings, said it looked forward to reviewing the data with the agency but would continue offering the test in the meantime.
Dr Myla Lai-Goldman, chief medical officer at LabCorp, said that OvaSure had been validated in several studies and that additional data were expected by the end of this year. Diagnostic tests typically are studied further after they have reached the market, she added.
Patients and advocacy groups are divided on the issue.
Ms Cara Tenenbaum, policy director for the Ovarian Cancer National Alliance, said there were people who 'are very excited about it' but the alliance wants to see more data first.
More than 21,000 new cases of ovarian cancer will be diagnosed in the US this year.
OvaSure measures the level of six proteins in blood, some produced by a tumour and some produced by the body in reaction to a tumour. It then calculates the probability of a woman having ovarian cancer.
In a study published in the journal Clinical Cancer Research in February, the test correctly classified 221 of 224 blood samples taken from women with ovarian cancer or from the control group. It identified 95 per cent of the cancers and its false positive rate - detecting a cancer that was not there - was 0.6 per cent.
However, Dr Beth Y. Karlan, director of the Women's Cancer Research Institute at Cedars-Sinai Medical Center in Los Angeles, said the samples tested were not representative of what might be encountered in routine screening.
There were very few blood samples from women with early stages of the most deadly type of ovarian cancer. 'That's really what we wanted to find,' she said.
The sceptics' biggest concern is not that the test will miss cancers but that it will say a cancer is there when it is not, thus subjecting women to needless surgery to have their ovaries removed.
The arithmetic is such, DrBerchuck of Duke said, that even if a screening test had a 1 per cent rate of false positives, it would mean that 30 out of 3,000 women tested might be subjected to unnecessary surgery for every one real case of cancer.
Ms Teresa Hills, 44, who had a visible mass on her left ovary, got a positive result from OvaSure. When the ovary was removed, the mass turned out to be benign.
Dr Lai-Goldman at LabCorp said that OvaSure should be restricted to women at high risk of ovarian cancer and that the test should be repeated if the result is positive. Those measures would limit the number of false positives.
LabCorp estimates that there are 10million women at high risk.
The ovarian cancer detection field has had disappointments before. Four years ago, the FDA intervened to stop the marketing of another complex ovarian cancer screening test developed by Correlogic Systems. The test, called OvaCheck, had also spurred great hope but never made it to market as experts questioned its validity.
With the number of genetic and other tests proliferating, the FDA has been under pressure to assure that the tests are accurate.
Dr Daniel Schultz, who oversees diagnostic tests for the FDA, said the agency has to balance demands for greater overview against concerns that regulation could impede development of needed diagnostic tests.
'We understand that concerns have been raised regarding the impact that FDA regulation would have on this whole field,' he said.
"Even if a screening test had a 1 per cent rate of false positives, it would mean 30 out of 3,000 women tested might be subjected to unnecessary surgery for every one real case of cancer."- Dr Berchuck
More than 90% of women with ovarian cancer will live at least five years if it is detected at its earliest stage
This story was first published in Mind Your Body, The Straits Times, on Sept 4, 2008.
