Shortly after receiving her  diagnosis in 2005, Mrs Canteri was enrolled in a clinical trial at Peter MacCallum Cancer Centre in Melbourne.

Doctors wanted to know if the addition of radiotherapy to a patient's lymph nodes under the arm pit — as well as to her breast — would do a better job of eliminating breast cancer.

The reason they wanted to test this was because only some women with breast cancer that had spread to their lymph nodes were having radiotherapy after surgery to remove the cancer.

If a woman's cancer had spread to many lymph nodes, she would generally receive radiotherapy to the area after surgery. But if the cancer had only affected a few lymph nodes, the woman would not typically receive radiotherapy after surgery.

A decade on, Mrs Canteri's clean bill of health  suggests these doctors were on to something.

A report about the major trial published in the prestigious New England Journal of Medicine this month said more comprehensive radiotherapy for breast cancer that includes the lymph nodes under the arm pit significantly lowers the chance of breast cancer returning.

The game-changing research found that 82 per cent of the women who received the additional radiotherapy to the lymph nodes remained cancer free, compared with 77 per cent who received radiation to their breast only.

The 10-year clinical trial, involving 1832 women with breast cancer that had spread to the lymph nodes, also found the additional treatment reduced the risk of cancer coming back in other parts of the body (such as the lungs or the liver) from 17.6 per cent to 13.6 per cent.

Mrs Canteri said she found it difficult to relax for five years after the surgery to remove her cancer because she worried it could still be "lurking in the background".

"Five years onwards you relax a bit and realise it is OK to be healthy and enjoy life because you are still around. It is a great feeling," she said.

The study's co-chair, Associate Professor Boon Chua of the Peter MacCallum Cancer Centre, said the additional radiation treatment to the lymph nodes was not yet a widespread practice.

"The results could change the decision-making of thousands of women across the country every year," she said.

Professor Chua said more than 15,000 Australian women were diagnosed with breast cancer every year and of those about one-third would have cancers that had spread to the lymph nodes.

But she warned the additional treatment carried the risk of side-effects such as a swollen arm, which women should discuss with their doctor. She said the women in the trial would also need to be monitored for any further side-effects.

Breast cancer is the third most commonly diagnosed cancer in Australia, making up about one in eight new diagnoses, and is responsible for about 2800 deaths per year.