Young breast cancer sufferers who have a family history of cancer are at higher risk of the ovarian form of the disease, and should be closely monitored, researchers say.

Each year, there are over 38,000 new cases in the UK. Around 20% of breast cancers occur in women under 40.

It is already known that women who carry the breast cancer genes BRCA1 and BRCA2 are at an increased risk of ovarian cancer.

But researchers from the Karolinska Institute in Stockholm, Sweden, say this does not account for all famillial breast or ovarian cancers.

Each woman has to be assessed individually

Professor John Smyth, Edinburgh University

They set out to examine how great this increased risk was.

They say young breast cancer sufferers with a family history of breast or ovarian cancers should be monitored closely by doctors.

Removing their ovaries (prophylactic oophorectomy), should even be considered in some cases to eliminate the risk of developing ovarian cancer, they suggest.

Reducing risk

Researchers looked at data for 30,000 women in Sweden, aged under 70, who had been diagnosed with breast cancer.

They also looked at data for 146,000 of the women's parents siblings and children to look at incidence of breast and ovarian cancer.

Researchers followed the women up six years later.

Of the 30,000, only 122 developed ovarian cancer. The researchers say the numbers are small, but they do raise issues about assessing and reducing women's risk of developing cancer.

Those under 40 who had a family history of ovarian cancer had a 17-fold increased risk of developing the disease themselves.

But this prediction was based on just three women in the study who fell into this group.

Based on five women who were diagnosed with breast cancer under 40 and had a family history of breast cancer, researchers found they had a five to six-fold increased risk of ovarian cancer compared to women in the general population.

Cancer incidence

Dr Kjell Bergfeldt of the department of medical epidemiology at the Karolinska Institute, who led the research, said: "The clinical implications of our findings are not obvious, especially because there is no effective screening strategy for ovarian cancer.

"However, provided that our results are confirmed by other investigators, they seem to allow identification, based on easily obtained clinical information, of a small subgroup of women with breast cancer who are at particularly high risk of ovarian cancer.

"In this subgroup, counselling, and perhaps even prophylactic oophorectomy, might be considered."

But he said he was not recommending ovary removal for all, but it was an option doctors and patients should consider."

He told BBC News Online this group of women needed to be closely monitored: "If by any means, women are at higher risk of developing ovarian cancer, then they should be in some kind of surveillance by doctors."

John Smythe, professor of medical oncology at the University of Edinburgh, said: "For women who have breast cancer at an early age, there's a high incidence of other cancers, including cancer of the ovaries."

"There is no doubt that there is that increased risk, but actually how big that risk is something that needs to be confirmed, and it's an evolving situation."

And he said ovary removal was not necessarily the solution for young women deemed to be at increased risk, particularly for those who had not yet had a family.

He added: "Each woman has to be assessed individually.

Professor Smyth said the research was important for the quantity of data it gave researchers, but stressed women should not be overly worried.

"A 17-fold increased risk on three women is not a reason for panicking."

The research is published on the website of The Lancet.