Liver tumours do not respond well to radiation

And latest figures showed that in 1998, 864 people died from intrahepatic cholangiocarcinoma.

Experts are unsure why death rates from this particular form of liver cancer have increased so dramatically, but say it could be related to environmental toxins.

Researchers from Imperial College School of Medicine in London published their findings in the journal Gut.

The reasons for the increase are not immediately obvious, said report author Dr Simon Taylor-Robinson.

Better diagnosis

Better diagnosis may be one possibility, or it could be that previous statistics did not reflect the true picture because liver cancer is so difficult to identify.

Thorotrast, a now banned substance that used to be used in radiology, smoking and alcohol, and an increase in environmental oestrogen have all been linked to this type of tumour.

But, say the authors, an increase in other environmental toxins may also have a role in the development of bile duct tumours.

Dr Taylor-Robinson said: "Something has to have changed and we wanted to find out what.

"In the 21st century we are exposed to hundreds of chemicals in our food and some of these get concentrated in the bile ducts.

"There are a few chemical compounds which have oestrogenic activity and some of these may cause bile duct cancers."

Rare cancer

Dr Taylor-Robinson stressed that this type of liver cancer is very rare compared to breast and colon cancer.

Bile duct tumours are not very responsive to drug treatment or radiotherapy and people usually die within three to six months of diagnosis.

Dr Taylor-Robinson said: "Further research has to be carried out to find out who is at risk and how we deal with it.

"This is important for the medical profession because they can screen people at higher risk."

The research team is also collaborating with the World Health Organisation (WHO) to identify patterns of this type of liver cancer.

Early indications are that it is more prevalent in industrialised countries.

But scientists are also exploring the theory that it could be linked to diet because Japan does not appear to see as many cases as the West.

Genetic factors are also being checked and tissue samples are being taken from patients with tumours to build up a tissue database for further research.

While interested in the results of the study, the Cancer Research Campaign (CRC) says it is too early to draw any conclusions.

A CRC spokeswoman said: "Little is known about the specific risk factors for this particular type of liver cancer, which is why epidemiological studies are so important.

"It is too early to say whether environmental carcinogens play an important role, especially as case numbers are relatively small. "