Image caption Ovarian cancer is hard to spot early on

A chemical in the blood could one day help doctors spot early signs of ovarian cancer, research suggests.

A US team found a marker antibody in the blood of women with ovarian cancer, but not in healthy ones.

Ovarian cancer is hard to detect at an early stage, which means it can remain hidden until it is advanced and very difficult to treat.

A cancer charity said the early findings were intriguing but required further study.

The work was carried out by a team at Rush University Medical Center in Chicago.

They tested women for antibodies to mesothelin, a substance found on the surface of ovarian cancer cells.

Some of the women had fertility problems (109), ovarian cancer (28), or non-cancerous ovarian growths (24), while the rest (152) were healthy.

Facts on ovarian cancer More than 6,500 women in the UK are diagnosed with ovarian cancer each year

The symptoms of ovarian cancer can be very vague, particularly when the disease is in its early stages

Early symptoms include:

Pain in the lower abdomen or side

Bloated, full feeling in the abdomen

Source: Cancer Research UK

The antibodies were found in the bloodstream of most of the women with ovarian cancer, as well as women with infertility due to problems with the ovary, the researchers said.

They were not present in healthy women or the women with non-cancerous ovarian tumours.

Lead researcher Dr Judith Luborsky said: "The finding is extremely important because at present medical tests are unable to detect ovarian cancer in its early stages, which is why death rates from this disease are so high."

Laura McCallum, Cancer Research UK's science information officer, said: "These early findings are intriguing, but further studies will need to be carried out in more women to confirm if this molecule could be useful in diagnosing cancer.

"Diagnosing ovarian cancer early is one of the most promising ways to prevent deaths from the disease and scientists, including our own, are continuing to look for new and improved ways of detecting it early so we can help more women survive."

The research is published in the journal Cancer Epidemiology, Biomarkers & Prevention, published by the American Society for Cancer Research.