THE first major indication that all was not well with Cathie Shearer, a Glasgow teacher of children with special needs, came when she woke up one January morning with a terrible pain in her side. ''I thought I had food poisoning or something,'' she says. ''I can stand quite a wee bit of pain, but it was really dreadful.''

Cathie was 44 and only two weeks previously her mother had died following a stroke. Cathie had been unwell for several weeks but after her mother's death, she felt so exhausted that one night she could hardly eat.

Doctors suggested various possibilities, including stress of bereavement and irritable bowel syndrome.

But during a trip to Canada several months later, a different possibility presented itself. As Cathie was getting off the plane in Calgary, she was hit by another wave of pain. After consulting a local GP, she was sent to hospital where she was examined by a young doctor. ''I went in at about 6pm,'' she recalls. ''There wasn't a bit of me he didn't test. I was there till 10pm and he said to me I would need to see a gynaecologist when I got home. He pointed me in the right direction and I'll always be grateful to him for that.''

Back in Glasgow, she went to the Samaritan hospital on Victoria Road, which has since closed. Sure enough, after examining her, doctors told her she needed a hysterectomy. When she came round from the operation, she was told the surgeons had found a ''huge lump'' in her ovaries and uterus. She had to have six weeks of radiotherapy before being given a cautious all-clear

Twenty-one years later, Cathie, now 65, retired and full of enthusiastic good humour, says that somehow, she never thought the disease would be life threatening. She had the support of many friends and the solace of her faith. It was the realisation she would never have children that hit her the hardest.

Next week, the effects of ovarian cancer are portrayed on screen by the Oscar-winning actress, Emma Thompson, in Wit, an American made-for-TV film based on the Pulitzer prize-winning play by

Margaret Edson.

Thompson plays Dr Vivian Bearing, a 50-year-old professor of English who has spent her life teaching the works of the seventeenth-century metaphysical poet, John Donne. When she is diagnosed with advanced ovarian cancer, the fiercely independent academic approaches it with characteristic wit and aggressive inquiry. But as time passes, she must let go of her assumptions about life and accept help.

Ovarian cancer support groups have welcomed the film for raising awareness about the disease that is the fourth most common cancer in women after lung, bowel, and breast cancers. It affects around 500

women a year in Scotland and around seven out of 10 sufferers die within five years.

Ovarian cancer attacks the ovaries, the organs that produce eggs and sex hormones. The most common form, 90% of cases, is epithelial ovarian cancer, affecting the surface layer of the ovary.

Early detection is difficult. There are often no symptoms and, even when there are, they could be due to many other conditions.

The causes are not well understood either. ''We will never find a definite cause, but we will improve our understanding of the abnormality of genes that cause it,'' says Nadeem Siddiqui, a gynaecological oncologist at Stobhill Hospital in Glasgow and one of Scotland's leading authorities on ovarian cancer.

''Most of it is a sporadic condition that occurs out of the blue for no known reason,'' he says. ''However, if you look at that sporadic group and look for common themes in those cases, one is that the women often have small family size and, in particular, no children. Having no children seems to add to the risk in some way.''

Repeated ovulation may damage the surface of the ovary. Inhibiting ovulation - by taking the pill, for instance - can therefore be a preventive measure. However, a lot of cases occur in women with no children, so it is by no means clear-cut.

Screening of women who have a strong family history of ovarian cancer is possible, but screening is not available generally, because, as Dr Siddiqui says: ''There is no evidence that screening for sporadic ovarian cancer is of any value at all.''

He advises any woman worried she could be at risk to take the combined pill. Sudden onset of new symptoms should be investigated.

In a small number of cases,

5%-10%, there may be a genetic link. Lesley Gower, 44, from Basildon, was diagnosed with ovarian cancer at 41 and discovered afterwards that there was a history of ovarian cancer in her family. Her three younger sisters have since been screened for cancer-causing genes. She now gives support to other sufferers through the support group, Ovacome.

The treatment of ovarian cancer, then, can be very effective and Dr Siddiqui, who is involved in producing a Scottish guideline for treatment, believes it is getting better. Suggestions that the mortality rate may be slightly higher in Scotland than in some other countries may well be due to nothing more than better collection of data here.

Dr Siddiqui has enthusiastically welcomed the establishment of a network allowing gynaecologists from district hospitals to consult their specialist colleagues on the best treatment for specific cases.

Cathie Shearer, now a member of the support group Tak Tent, believes that maintaining a positive state of mind is important. She recalls the words of Fiona Castle, the wife of the broadcaster Roy Castle who died of lung cancer in 1994: cancer is a word, not a sentence.

Wit, BBC2, 9pm, Tuesday.

Ovacome can be contacted on 0207 600 5141 or at

www.ovacome.org.uk

l What are the symptoms?

Ovarian cancer does not generally cause symptoms in the early stages. Later, tumour growth in the pelvis can cause a range of symptoms including pain, a swollen abdomen, frequent urination, constipation, loss of appetite and shortness of breath. However, these are all more likely to be caused by much more common conditions than ovarian cancer.

Doctors advise that the sudden onset of such symptoms should be investigated.

l What causes it?

The cause is unknown but certain factors appear to influence risk. Most cases happen in women who have been through the menopause. More than half of cases occur in the over-65s. Family history is the most important factor but even so, fewer than 10% of cases have family history of the disease. Where a family member has had it, that is not proof there is a cancer-causing gene in the family - the patient could have developed the disease by chance. The frequency of ovulation also appears to influence risk. Women who have small families and, in particular, no children at all, are slightly more susceptible.

l Can it be prevented?

In the small group, 5%-10%, who have several close relatives who have had the disease, it may be possible to screen for genes that can mutate to cause ovarian cancer. It may also be possible to remove the ovaries to prevent the onset of the disease. This is called a prophylactic oophorectomy which makes a younger woman menopausal. In the meantime, taking the combined pill, which inhibits ovulation, has been shown in epidemiological studies to reduce the risk.

l What is the treatment?

The first line of treatment is surgery to remove as much of the cancer as possible. The ovaries, fallopian tubes and womb are usually removed. Chemotherapy often follows. Radiotherapy is rarely used in the treatment of early-stage ovarian cancer.