Thousands of women with advanced ovarian cancer could benefit from an expensive drug, says a government watchdog.

The National Institute for Clinical Excellence (NICE), which assesses new drugs for their cost-effectiveness, says that topotecan may be suitable for women who have failed to respond to ordinary chemotherapy.

In theory, as many as 1,800 women could receive the drug each year, at an annual cost of �7m to the NHS.

Only approximately 30% of women are alive five years after a diagnosis of ovarian cancer.

This is because symptoms often only appear once the disease has spread, making it much harder to treat.

Most women who develop the cancer are given a combination of drugs, including Taxol, which was also approved by NICE in the past year.

Totally bedridden

Topotecan should only be given, say experts, if this combination has failed to eradicate the cancer, and then only to those patients whose illness has left them completely bedridden and unable to care for themselves.

Professor Peter Littlejohns, NICE's clinical director said: "Ovarian cancer is a common cancer, affecting 6,000 women in England and Wales each year.

"For some of these women the cancer will return after their initial chemotherapy and at this stage of their disease the women and their doctors will consider the benefits of further treatment.

"Today's guidance is clear that topotecan should be one of the technologies they consider."

Just as Taxol, and other drugs like it, are derived from the bark of the yew tree, Topotecan, is made from the oriental tree Camptotheca acuminata.

It works by stopping the DNA in cancer cells replicating, thus slowing down their spread.

Approximately 360 women in England and Wales are already getting the drug, marketed as Hycamtin - but another 1,500 are likely to get it following this guidance.