Researchers in California have identified a molecular signal in the blood that can reveal ovarian cancer at its earliest precancerous stage, long before a tumour forms or symptoms appear. The signal, an RNA molecule called Tu-Stroma, detected the precancerous condition known as serous tubal intraepithelial carcinoma, or STIC, in 92.3 per cent of the women who had it in a validation group, while correctly identifying 98.2 per cent of healthy women, according to a study published on 10 November 2026 in the journal Nature Medicine.
The work, led by researchers at the Hoag Family Cancer Institute in Newport Beach, offers the first realistic prospect of a blood-based early warning system for high-grade serous ovarian cancer, the most common and most lethal form of the disease. Ovarian cancer is usually diagnosed only after it has already spread, because it produces few symptoms in its early stages and there is no reliable screening test — which is why a blood test that could catch it years earlier would be transformative.
The discovery comes from an eight-year, international, multi-institutional study led by Dr Rajan Gogna, director of translational research at Hoag, and Dr Esha Madan, principal investigator of the cell competition in the tumour microenvironment laboratory at Hoag. The team focused on high-grade serous ovarian cancer, a subtype that often begins not in the ovary itself but in the fallopian tube, as STIC — a group of microscopic abnormal cells that cannot be seen on imaging scans or picked up by conventional cancer blood tests.
Tu-Stroma is an RNA molecule associated with one of cancer's most fundamental biological processes: the way a developing tumour weakens neighbouring healthy cells to make room for its own growth. The researchers found elevated blood levels of Tu-Stroma in women with both STIC and early-stage high-grade serous ovarian cancer, suggesting that the signal appears at the very start of the disease process, before a tumour has formed.
In the validation group, the test detected STIC in 92.3 per cent of the women who had it and correctly identified 98.2 per cent of healthy women. When the researchers modelled how the test might perform in a high-risk population, they found that about 72 per cent of positive results would be accurate — meaning roughly three in ten positives would be false alarms needing follow-up — while a negative result would be correct nearly 100 per cent of the time.
The researchers are careful to stress what the study does not yet prove. The analysis used previously collected blood samples from women with confirmed diagnoses, so it does not yet show that the test can predict, in real time, which women will go on to develop cancer. Tu-Stroma is a research discovery, not a clinical test: no patient can ask a doctor for it today, and further studies following women over time are needed before anyone knows whether it works well enough for routine care.
Hoag researchers are now planning prospective clinical studies involving women from Hoag and the broader community, including those with and without an elevated genetic risk of ovarian cancer. The long-term goal is to translate the discovery into a clinically validated blood test that could transform ovarian cancer surveillance and prevention, particularly for women with BRCA gene mutations and other risk factors, who currently face the stark choice of intensive surveillance or preventive surgery.
Ovarian cancer kills tens of thousands of women every year, largely because it is found too late. If a blood test could reliably flag the disease at its precancerous stage, doctors could intervene years earlier, when treatment is far more likely to succeed. The Tu-Stroma finding does not deliver that test yet, but it is the first time science has found a signal in the blood that points to the very beginning of the disease — and that, the researchers say, is where the hope lies.
