Stem cell transplants do not benefit patients with breast cancer, research has shown.
It was hoped stem cells could help treat breast cancers
Studies had suggested they improved the success of chemotherapy in patients with breast tumours.
But Swiss research, published in the journal Annals of Oncology, found the transplants had failed to live up to early hopes.
However the transplants do help some patients with blood cancers, as the illnesses react differently.
Stem cell transplants have been used in cancer treatments as a way of trying to enable the body to cope with high doses of chemotherapy and radiotherapy.
Both treatments can severely damage bone marrow cells because they, like cancer cells, reproduce rapidly.
This prevents the body from being able to make the blood cells needed to carry oxygen, defend against infection, and prevent bleeding.
In a bone marrow transplant, marrow containing healthy stem cells is given to patients to replace damaged cells.
It was hoped that using stem cell transplants to boost the bone marrow supply would allow tumours to be treated with one big dose of chemotherapy, rather than a series of smaller doses.
Stem cells are the body's master cells, with the ability to become many different types of tissue.
An international research team has looked at transplant numbers in Europe since 1991.
They found that the use of stem cell transplantation in breast cancer treatment soared in the early and mid 1990s.
Nearly 28,000 transplants were carried out for various types of solid tumours in Europe between 1991 and 2002.
Breast cancer accounted for around half of the procedures (more than 13,500).
The number of transplants given to breast cancer patients rose from 94 in 1991 to 2,629 in 1997.
But, from that year, numbers fell sharply as studies revealed stem cell transplants had little benefit.
In 2002, just 330 breast cancer patients received stem cell transplants.
Professor Alois Gratwohl from the Department of Internal Medicine at Kantonsspital Basel in Switzerland, who led the research, said: "Most recent results remain ambiguous and the value of stem cell transplant in breast cancer still needs to be determined in selected categories."
He added: "What is encouraging is that the fall in the numbers of stem cell transplants illustrates that doctors have been quick to react to the negative findings in the trials and to share that information."
Dr Raj Chopra, an specialist in the biology of drugs at University College London, told BBC News Online: "Stem cell transplants were thought to be the big thing for breast cancer patients in the 1990s.
"The hope that giving one big dose of chemo would eliminate the need for a difficult course of the therapy hasn't been borne out.
"Also, new treatments such as drugs have been developed, so transplants have to be compared to those newer approaches."
But he said blood cancers such as leukaemias could be treated using stem cell transplants.
"There, giving that big dose to some patients does help because their tumours are more chemo-responsive."