A test using two chemotherapy agents to treat breast cancer was halted after two women in the study died, French researchers reported on Tuesday.

The test involved a combination of doxorubicin and docetaxel and followed a line of research that has shown combinations of certain breast cancer drug types are better that one kind alone to combat advanced and spreading breast cancer, the report said.

“In conclusion, this study shows that the doxorubicin-docetaxel combination is associated with an increased risk of severe ... and life-threatening complications,” said the study appearing in this week’s Journal of the American Medical Association.

Researchers should be aware of the potential toxicity of the combination, added the study.

The research was done by the Huguenin Cancer Center, Saint-Cloud, France and involved 627 women ages 18 to 70. The aim was to extend their survival for at least five years.

It began in 1999 and was halted in January 2003, following two deaths related to drug poisoning as well as one case of peritonitis, an inflammation of the membrane of the abdomen.