The head of the national cancer control programme, Professor Tom Keane has said that by late spring, all initial breast cancer diagnosis and treatment will be centralised at eight hospitals in the country.
There were 33 hospitals providing these services just over a year ago.
Prof Keane said that over the coming period services are due to move from Our Lady of Lourdes in Drogheda, Tallaght Hospital, the South Infirmary in Cork and Sligo General Hospital.
He said that dialogue was continuing with Sligo General, where there has been a major campaign of opposition to the move.
Prof Keane insisted that he had been extremely sensitive to the need of patients in the changes.
He promised that services would not transfer from Sligo until he was satisfied that alternative and excellent services were in place.
Prof Keane and Health Minister Mary Harney met with medical specialists at Sligo ten days ago to discuss the issue.
He said that his goal was to get Ireland into the top 10 to 15% of top performing countries in terms of cancer care but this would take many years.
His remarks came as he was met volunteers in Dublin at the launch of the Irish Cancer Society's plans for its Daffodil Day on 20 March.
The society has expressed concern at the potential impact of the economic downturn on its fundraising efforts, particularly free-night nursing service for patients at the end stage of the illness and homecare teams.
Chief Executive John McCormack said it needs to raise around €4.2m this year to run services such as hospital-based cancer liaison nurses and the National Cancer Helpline.
Mr McCormack said that 25,000 people will develop cancer this year and one in three during their lifetime and the services provided by the society are need now more than ever.