Los Angeles ? Recent advances in breast cancer awareness and treatment have made routine mammography less crucial in detecting cancer and mitigated its value in reducing deaths, researchers reported Wednesday.

Although the World Health Organization and U.S. authorities have found previously that mammography reduces deaths from breast cancer by about 25 percent, the new study in the New England Journal of Medicine determined that the death rate dropped by only 10 percent following the introduction of routine mammography in Norway.

The reduction was “far less than we expected,” said Dr. Mette Kalager, a surgeon at Oslo University Hospital and the study’s lead author. In fact, during the period covered by the study, the death rate among women over 70 — who did not undergo mammography but received the same care as younger women — dropped by 8 percent. That suggests that the benefit of mammography may have been as little as 2 percent, Kalager said.