Sept. 13 (HealthDay News) -- In a disheartening result that confounds existing research, a team in France says a new stem cell therapy for a rare kidney disease is no better than the usual chemotherapy-only approach.

The study "has major limitations and must be interpreted with caution," said Dr. S. Vincent Rajkumar, a professor of medicine at the Mayo Clinic. Still, he said, it conflicts with "a widely held belief" that the stem-cell approach -- combined with aggressive chemotherapy -- is better for some patients.

But there's also some good news. The study doesn't reject the possibility that stem-cell transplants may be a better bet in facilities that specialize in the procedure, Rajkumar added.

The findings are published in the Sept. 13 issue of the New England Journal of Medicine.

AL amyloidosis disease is one of several caused by abnormal proteins that deposit themselves in various organs of the bodies and cause major damage, Rajkumar explained.

An estimated 1,200-3,200 people will develop the condition in the United States each year. The disease is similar to a more common condition called multiple myeloma.

Survival with AL amyloidosis is typically measured in months. The average survival time is a year without an effective treatment, said study lead author Dr. Arnaud Jaccard of the Centre Hospitalier Universitaire in Limoges, France.

But, according to Jaccard, there's plenty of controversy about which treatment is best.

In the new study, researchers followed two groups of 50 patients each. One group received treatment with high-dose chemotherapy (a drug called melphalan) followed by stem cell transplants; the other received standard-dose melphalan-plus-dexamethasone chemotherapy.

The researchers followed the patients for an average of three years to see what happened to them.

The team found no major difference in survival between the two groups.

There are some caveats, however, Rajkumar said. For one, few patients took part in the study, lowering its statistical power. For another, many of the patients who received stem-cell transplants got them at facilities that didn't have much experience in the procedure, which is very complicated, he said.

Considering that, it's possible that treatment with stem-cell treatments may be a better option in some cases, Rajkumar said.

SOURCES: S. Vincent Rajkumar, M.D., professor, medicine, Mayo Clinic, Rochester, Minn.; Arnaud Jaccard, M.D., researcher, Centre Hospitalier Universitaire, Limoges, France; Sept. 13, 2007, New England Journal of Medicine