LONDON, Oct 8 (Reuters) - A new mammogram technique could lead to earlier diagnosis and improved survival rates for breast cancer patients, British researchers said on Monday.

The new method is expected to remove many of the uncertainties in mammograms by giving doctors a better idea of the exact size and density of a suspected tumour.

Professor Michael Brady of the University of Oxford, where the technique was developed, said it can detect breast lumps as small as one millimetre (0.04 inch) across, which is 10 times smaller than those that can be detected with traditional mammograms.

A lump shows up on a mammogram as a bright or dense spot on a grainy background. But the size of the spot can differ depending on the machine, the type of film used or how it is developed.

"We have found a way of eliminating all these variations and leaving only the interesting information -- the size of a patch of dense tissue," Brady said in a statement.

Using the technique, the researchers can determine the density of the suspicious patch in millimetres. Spotting a lump at its smallest and earliest stage is extremely important because the sooner cancer is detected and treated, the greater the chance of beating it.

Brady and his team are planning to test the technique on 500 healthy women over two years to see whether and how the disease develops in them. They are particularly interested in testing the technique on women who are taking hormone replacement therapy (HRT).

The risk of developing breast cancer increased by 30 percent after 10 years on HRT, which replenishes female hormones that diminish after the menopause.

Each woman will be given two scans over the two-year period and the scientists will compare them for any changes.

"We believe there will be a common pattern of the mammograms of women who go on to develop breast cancer, and that even the tiniest patches may indicate increased risk. Based on our study, doctors will then be able to examine mammograms more thoroughly to look for the early signs," Brady added.

Breast cancer is the most common cancer in women. An estimated one in eight women will get the disease sometime during their life. If the cancer is diagnosed early the five-year survival rate is as high as 95 percent.