A new study claims that precision medicine is better helping patients and physicians decide whether chemotherapy is needed, and thus potentially saving a huge amount of unnecessary pain and suffering as a result.

Researchers used a test to assess the risk of breast cancer recurrence and determine how successful chemotherapy is likely to be, examining 21 genes that are known to be tied to cancer recurrence, according to a statement from the University of Michigan Health System.

A total of 1,527 women were surveyed who had early stage breast cancer. Scientists compared those who had the 21-gene recurrence score assay test to those who received chemotherapy. The study found that 87 percent of patients who had a high score in the test got chemotherapy, and of those with the lowest test scores, just 3 percent got chemotherapy.

“The idea of precision medicine is to give patients the treatments that are the most likely to help and avoid needless side effects,” says study author Christopher Friese, Ph.D., R.N., a professor at the University of Michigan School of Nursing.

“Chemotherapy has substantial side effects. Improving chemotherapy recommendations to those who truly stand to benefit would reduce complications and improve quality of life for many women,” Friese says.