WOMEN'S HEALTH TECH REPORT: Are Multi-Cancer Blood Tests Ready for Prime Time in ObGyn?
Not quite
Summary
Multi-cancer early detection (MCED) tests are blood tests that look for signs of cancer in the bloodstream. Right now, about 40 of these tests are either for sale or being developed.
They work by detecting tiny fragments of DNA that cancer cells shed into the blood. The Galleri test, made by a company called Grail, is one of the most studied. It just completed the largest randomized trial of any MCED test ever run, enrolling about 142,000 people through the UK’s National Health Service.
The trial tested whether annual Galleri screening could reduce the number of late-stage cancer diagnoses. It did not meet its main goal.
For gynecologic cancers specifically, existing tests already screen for cervical and breast cancer, but there is no good screening test for ovarian cancer, one of the deadliest cancers in women. MCED tests are being watched closely for this reason.
What It Means
For women’s health, the promise of MCED tests is most meaningful for cancers we currently cannot screen for well. Ovarian cancer is the clearest example. It is usually found late, when it is much harder to treat, because there is no reliable, widely recommended screening test. MCED tests could, in theory, change that. But the current data are sobering.
These tests correctly identify cancer in only 30 to 80 percent of people who actually have it. And in one Galleri study, nearly half of people who got a positive result did not actually have cancer. False positives in gynecologic cancer screening are not a minor inconvenience. They lead to imaging, surgery, and serious anxiety. For cervical cancer, where we already have a highly effective screening system, MCED tests are not more sensitive than existing tools and could give false reassurance if women skip their Pap smears. Whether catching cancer earlier with these tests actually saves lives has not been proven yet.
My Take
I understand why a Super Bowl ad showing a man relieved by a negative cancer test is appealing. Fear of cancer is real and universal. But the science is not there yet, and in gynecologic oncology, the stakes of getting this wrong are high. The Galleri trial just failed its primary endpoint. In the previous large Galleri study, 38 out of 92 positive tests were real cancers. That means 59 women out of every 92 with a positive result did not have cancer. In a gynecologic context, those women may have gone on to have unnecessary imaging, biopsies, or surgery. Ovarian cancer is the one area where MCED tests hold genuine promise because we have nothing better. But that promise requires rigorous trial data showing actual survival benefit, not just earlier detection. Early detection of a cancer that still kills the patient is not a win. I will be watching the full NHS-Galleri results closely. Until we see them, I would not recommend these tests outside a clinical trial.