(NaturalNews) A controversial breast cancer treatment consisting of a combination of high-dose chemotherapy and a stem cell transplant does not extend the lives of patients, according to a study conducted by researchers from the University of Texas' M.D. Anderson Cancer Center in Houston and presented at the San Antonio Breast Cancer Symposium."This report should absolutely, definitively and for all time close the door on this treatment," said Dr. Larry Norton of the Memorial Sloan-Kettering Cancer Center.During the 1980s and 1990s, it became popular to treat women with a high dose of chemotherapy after surgery, in order to kill off any cancer cells that had not been removed by the initial procedure. Before surgery, surgeons would extract stem cells from the patient's bone marrow. After the chemotherapy, these cells would be transplanted back into the body in order to restore the immune cells that had been killed by chemotherapy.The procedure was controversial from the start, in part due to the toxicity of chemotherapy drugs. Such drugs are particularly dangerous at high doses, and some women subjected to the treatment in the United States have died from toxicity. Even in those who survive, such a high dose of chemotherapy drugs is incredibly hard on the body and leads to a high degree of suffering. Finally, many health insurers were initially unwilling to pay for what they considered an experimental and non-proven treatment.Researchers analyzed the results of 15 separate trials involving a total of 6,200 early stage breast cancer patients. The lymph nodes of all the patients tested positive for cancer following surgery, but in no cases had the cancer spread to other organs. The researchers found that women who underwent the high-dose chemotherapy did not relapse as quickly as women who underwent more conventional treatments, but they did not live any longer."I was surprised by the results," said lead researcher Donald Berry. "I was expecting some subsets of women to show some survival benefit."