MONDAY, June 27 (HealthDay News) -- Even though radiation after mastectomy for advanced breast cancer has been proven to save lives and multiple guidelines call for it, nearly half of these patients don't receive it, researchers say.

Between 1999 and 2005, only 55 percent of older high-risk breast cancer patients who should have undergone radiation therapy actually received it, according to the study that appears online June 27 in the journal Cancer.

"When physicians are not guided by published evidence, there is the chance that patient outcomes will suffer or that patients will undergo unnecessary treatments and tests," study co-leader Dr. Shervin Shirvani, of the M.D. Anderson Cancer Center in Houston, said in a journal news release.

The M.D. Anderson Cancer Center scientists analyzed data from 38,322 older women with advanced breast cancer who underwent mastectomy (partial or complete removal of one or both breasts) in the United States between 1992 and 2005.

Following the publication of clinical trials that revealed its benefits, the use of radiation after mastectomy increased from 36.5 percent in 1996 to 57.7 percent in 1998, the researchers found. However, no further increase occurred between 1999 and 2005, despite the release of a number of major guidelines endorsing it.

The researchers expressed concern that so many providers appear to be ignoring the evidence-based guidelines.

"Beyond the potential for distress and injury to the individual patient, there is also the strong likelihood that medical resources will be wasted on unproven or ineffective treatments," Shirvani said.

More needs to be done to make sure that helpful findings from clinical trials are widely implemented in patient care, the researchers concluded.

More information

The American Cancer Society has more about surgery for breast cancer.