I would not want to alarm women on the basis of one study

Dr Louise Brinton, National Cancer Institute

And they have no idea why the risk of brain and lung cancers is higher.

The study was conducted by Dr Louise Brinton, chief of the NCI's environmental epidemiology branch.

She told the New York Times: "What the study showed is no difference for most of the cancer sites, which I think is good news.

"And for the few sites which we did find differences, we have no ready explanation.

"So I would not want to alarm women on the basis of one study."

Most had silicone

The study involved nearly 13,500 women who had breast implants before 1989.

Over the following 13 years, their progress and health was compared with a control group of 4,000 other women who had plastic surgery.

On average, the women were 34 when they received the implants, most of which were silicone, and all of them kept them for at least eight years.

Of the women, 10% had saline implants - but the type of implant had no bearing on the results.

Women in the implant group were three times as likely to die of diseases of the respiratory tract, primarily lung cancer, and twice as likely to die of brain cancer.

Implants withdrawn

Some experts believe that silicone gel has the capacity to migrate to the lung.

Silicone implants were withdrawn by the US Food and Drug Administration in 1992 - the EU is still considering their safety.

Many women with silicone implants have opted to have them removed. Some research has found that a high proportion of the implants had suffered some sort of rupture.

Many recipients are also convinced that silicone implants have contributed to auto-immune and connective tissue diseases.