Many common medical treatments have never been tested in a clinical trial. A new study published in the July issue of Health Affairs highlights how evidence from trials of untested but widely used treatments can change medical practice and help patients.

A clinical trial with results published in 2011 found that certain women with early stage breast cancer do not benefit from surgery, called axillary dissection, to remove lymph nodes. The procedure can lead to arm swelling and other painful side effects.

Experts were unsure whether the study results would cause physicians to change how they treat patients. David Howard, PhD, associate professor of health policy and management at Emory’s Rollins School of Public Health, led a subsequent study that showed use of the axillary dissection declined immediately after the results of the clinical trial were released. The proportion of women who met the trial inclusion criteria and underwent axillary dissection dropped roughly in half, from 60 percent before the trial to 30 percent after the trial.

The results challenge the conventional wisdom that physicians are slow to react to new evidence. "The trial had a large and rapid effect on how patients are treated," explains Howard. "This potentially spared many women from arm swelling and other painful side effects." The study highlights the value  to patients and the health system of conducting clinical trials of established medical practices.

"This is another example of how trials of widely used but untested medical practices, of which there are many, can change the way that physicians treat patients, thereby improving patient health and reducing costs," says Howard.