Women are dying unnecessarily of ovarian cancer because GPs fail to spot warning signs, according to experts.

Large numbers of family doctors cannot correctly identify the cancer's symptoms, according to a major study published today. It found that 37% of women visit their GP several times before their cancer is detected, and 65% are not referred for a test right away.

The charity Target Ovarian Cancer's study, in which leading doctors played a key role, found widespread ignorance among GPs about the symptoms and that some mistook it for other, less serious illnesses such as irritable bowel syndrome.

The study found that 44% of women had to wait more than six months for a correct diagnosis and 37% had to visit their GP between three and five times before they were referred to a cancer specialist. Some 65% said they were not immediately referred for a blood test or internal scan.

"Some GPs miss ovarian cancer. That's a real problem as the delay could cost the woman her life, and at a minimum causes her a lot of anxiety. The sad fact is some women are dying from late diagnosis of ovarian cancer," said Dr Willie Hamilton, senior research fellow at Bristol University and study advisory panel member.

Ovarian cancer claims 4,300 lives a year in the UK. It is hard to detect because it lacks one telltale symptom, unlike a breast lump in breast cancer or bleeding for bowel cancer. Some 96% of the 400 GPs interviewed in May for the study said they believed ovarian cancer is a "silent killer".

Prompt diagnosis is crucial because while 80%-90% of women whose cancer is detected early survive for at least five years, that figure falls to just 25% when the disease is spotted late, once it has spread. Diagnosis in the UK typically takes until a year after symptoms have appeared.

Diagnostic delays of as little as a week may impact on some chances of treatment helping prolong life, said Hamilton.

"Anything that can expedite diagnosis may cut the death toll," added Hamilton. GPs who may not usually consider ovarian cancer as a possible diagnosis because of its vague symptoms should be more willing to do an internal examination or refer women for ultrasound scanning or to a gynaecologist, he said.

"There is considerable scope for earlier diagnosis in this disease," said Professor Bob Haward, associate director of the National Cancer Research Network and chairman of the study's group of advisers.

"A lot of women at present are diagnosed with advanced disease that is associated with poor survival rates. But for some earlier diagnosis may have been possible." Earlier detection could result in better prospects, he added.

Ovarian cancer is the deadliest gynaecological cancer Some 6,800 women are diagnosed with it each year, mainly the over-50s. The UK has one of the worst survival rates for it in Europe, partly due to late diagnosis.

Previous similar studies have also identified a trend of later diagnosis in the UK compared to other countries as a key factor in breast cancer survival, said Professor Michel Coleman, an expert in cancer diagnosis at the London School of Hygiene and Tropical Medicine.A survey of 1,000 women revealed very low knowledge levels about both ovarian cancer's symptoms, such as a distended stomach and abdominal pain, and its risk factors, which include childlessness.

Annwen Jones, Target Ovarian Cancer's chief executive, said the Department of Health should mount an urgent, high-profile campaign to increase women's and GPs' understanding of the disease. "We're worried that women are losing their lives who might otherwise have survived. Delays in diagnosis can never be good news," she said.

Professor Steve Field, chairman of the Royal College of General Practitioners, said the disease was "notoriously difficult to diagnose" but agreed that family doctors needed to detect it more consistently. "GPs should be more aware of the possibility of ovarian cancer and if there are any doubts should refer for a specialist opinion," said Field. "There's no doubt that the later presentation of symptoms, and on occasion delayed referral, will contribute to the death of women, and anything we can do to improve that situation, we should." Health minister, Ann Keen, said the study "identifies the challenges and opportunities of improving survival and quality of life for women with ovarian cancer. As a nurse, I understand how important early detection is in helping to fight this deadly disease. The Department of Health is working to improve survival rates, "especially in the area of symptom awareness amongst women and GP," she added.