December 2008
Blood test for ovarian cancer marketed for use in diagnostic setting
A blood test for ovarian cancer, known as OvPlex™, is being marketed to general practitioners for use in the diagnostic setting.
Background
There is currently no screening test for ovarian cancer. Over 70 per cent of cases of ovarian cancer are detected at an advanced stage where the cancer has spread and is difficult to treat successfully.
A combination of tests is currently used to diagnose ovarian cancer including physical examination, an ultrasound or CT scan and a CA125 test.
CA125 is a protein found in the blood. It is known as a tumour or cancer marker as increased levels may indicate ovarian cancer is present. However, CA125 is not appropriate to use as a stand-alone test for ovarian cancer as there are a number of other causes for raised CA125 levels including ovulation, menstruation, endometriosis, fibroids or benign ovarian cysts. Additionally, about 50 per cent of women with early-stage ovarian cancer will have normal CA125 levels.
About OvPlex™
OvPlex™ uses five protein biomarkers, including CA125 and is being marketed as a diagnostic test for ovarian cancer. On 28 October 2008, OvPlex™ was released in Australia, marketed as a diagnostic test for women suspected of having ovarian cancer. The test is initially available through general practitioners in Melbourne at a cost of $200 to the patient with plans to roll the availability of the test out across the country. OvPlex™ is not being marketed for use as a population screening test.
Recent media coverage (West Australian, 9 December 2008) has reported two more biomarkers have been added to create a second generation test, OvPlex™ 2G. The West Australian reports that the company plans to conduct a trial of this second generation test on 350 cancer samples.
National Breast and Ovarian Cancer Centre comment
No data on OvPlex™ have been reported from prospective controlled clinical trials. The only data available come from the test developer and as yet remains unpublished in peer-reviewed literature. This unpublished research reports that a phase II biomarker trial involving 150 ovarian cancer samples and 212 controls found OvPlex™ to have an overall *sensitivity of 94.1%, a specificity of 91.3% and an accuracy of 92.7% across all disease stages. For the detection of ovarian cancer in its early stages (stage I/II), OvPlex™ was reported to have a sensitivity of 91.9%, a specificity of 91.3% and an overall accuracy of 91.6%.
There are currently a number of tests in development worldwide which aim to detect ovarian cancer in its early stages through the presence of protein biomarkers in the blood. OvPlex™ is one of these tests, being marketed for use in the diagnostic setting rather than the population screening setting. However, it is important to note there is currently no evidence that OvPlex™ is able to detect a greater proportion of early stage cancers than CA125 and thus have any impact on ovarian cancer mortality.
Given the high mortality from ovarian cancer, new research into ways of increasing the early detection of the disease is important. These tests may have a role to play in the future in improving the detection of ovarian cancer. However, further validation in large clinical trials is required before they could be recommended for routine use either in the diagnostic or screening setting. At this time, general practitioners should continue to follow NBOCC’s guide to the Assessment of symptoms that may be ovarian cancer, which recommends the use of ultrasound and CA125 if findings upon clinical examination are suspicious.
* Sensitivity refers to the test’s accuracy in being ‘positive’ if the woman does have ovarian cancer. Specificity refers to the test’s accuracy in being ‘negative’ if the woman does not have ovarian cancer.
