But a report presented to the conference yesterday, also shows that 37 per cent who were involved in treatment choices had problem in making decisions for themselves.
Increasingly, women are asking to be more involved in their breast cancer care.
However, Professor Michael Baum, a breast cancer specialist at the Royal Marsden Hospital in London, said that not all women wanted to choose. 'Some women want us to be paternalistic, although it is not politically correct for us to be so.'
The research, in which he collaborated with the London Hospital Medical College, showed that more than one in five could not make a decision, or experienced considerable difficulty in doing so.
'Of the 62 women with genuine choice, 69 per cent chose local excision, but 31 per cent chose mastectomy,' the researchers said.
Professor Baum said it must be made clear to women that choosing to leave the decision to the surgeon was also an acceptable choice in itself.
Breast cancer is still the commonest cancer in women in the UK, with 24,000 new cases a year and 15,000 deaths.