Promising but preliminary studies of the ability of a blood test to detect the presence of ovarian cancer were heralded in a company press release and picked up in this Reuters story.
Although devoid of many evidentiary details, this text’s bigger problem is that it turns unpublished pilot studies into news. The blood test has a long way to go to surmount regulatory hurdles, and success is uncertain. Better to wait, we think, until more evidence is in hand.
Early and accurate diagnosis of ovarian cancer is a high priority, as many of these cancers are found too late to permit long-term survival. Existing blood tests for the early diagnosis of ovarian cancer have a relatively high sensitivity to detect the disease but are limited due to their false positive rate. A more sensitive and specific test would be a clear advancement.
While the intended audience may be investors, and not the general public, this story is easily discoverable and will likely be read by patients and loved ones. But sharing diagnostic news prematurely and incompletely is problematic, as stories such as this could send many women to their doctor’s offices looking for help that is simply not yet available.
Cost is not discussed here. Cost is always a consideration when discussing a new testing method. The existing blood tests (CA-125 and OVA-1) are relatively inexpensive ($60 and $650 respectively). Although this new method may be more sensitive and specific, its cost effectiveness is uncertain at the moment.
Existing tests have a relatively high ability to identify ovarian cancer (known as “sensitivity”) but are hampered by false positives (50% specificity). The story attempts to quantify the benefits of the test (“…correctly identified cancer in up to 95 percent of cases…” and “The test was nearly twice as successful in eliminating false-positives than current tests.”) but does not do so adequately. We would have liked to have seen a quantification of the specificity rate to meet this criterion–how many tests come up as positive for ovarian cancer, but are actually wrong (false positive)?
Although the rate of false positive diagnoses in the pilot studies described here were quite low, they still occurred. The story would benefit from directly addressing that and other possible debits of the test.
Sadly, this story appears to have jumped the evidentiary gun. The British company that funded the studies, Angle, generated a press release based on two relatively small (200 patients per study) proprietary pilot studies that have not yet been subjected to peer review. Even worse, those studies are only the first in an evidentiary chain of clinical studies needed to allow regulatory bodies to evaluate this blood test for commercial use.
Ovarian cancer diagnosis is a difficult challenge.
The story’s sole source is clearly identified as the chief executive of the company that appears to have funded the work. But the presence of only that source is a problem, as the text offers no independent viewpoints.
The story dances around a key issue, that of comparative effectiveness. Although the point of this story is that this new blood test does a better job of detecting ovarian cancer than do available diagnostic tests, the story offers no information about those alternatives.
The story indicates that further studies are needed to fulfill European and US regulatory requirements, implying that the test is not yet available. But the comments of the company spokesperson make the likelihood of approval seem like a foregone conclusion.
There are multiple efforts to utilize the detection of circulating tumor cells (CTC’s) as a method of early redirection of cancer. The technology has been under study for a number of years. So, while perhaps an improvement over existing methods, the test method is not novel. We have repeatedly taken issue with the use of “breakthrough” in stories and this one is no exception. If the results of this relatively small study are repeatable, the Angle test would be an improvement over existing methods.
Parts of this story (a direct quote, for example) are independent of the company’s news release.
Systematic, Criteria-Driven
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