CHICAGO, June 4 (Xinhua) -- The presence of cancer cells in the blood of patients with early-stage breast cancer may be predictive of a benefit from radiotherapy delivered after surgery, according to a study posted on the website of Northwestern University (NU).

The researchers analyzed data from two cohort studies, covering more than 3,000 patients with early-stage breast cancer who had been tested for circulating tumor cells (CTCs), kind of cancer cells that have shed from the primary tumor and circulate in the patient's bloodstream.

They discovered that patients who had at least one CTC in their peripheral bloodstream demonstrated significantly longer survival and decreased the risk of local recurrence if they received radiation therapy after surgery.

The researchers further found that patients who did not have CTCs in their peripheral bloodstream showed excellent outcomes whether they received radiation therapy or not.

CTCs are found in an estimated 15 to 25 percent of patients with early-stage breast cancer.

"Our findings provide initial robust evidence that testing for circulating tumor cells may be an important tool in helping to guide recommendations for radiation therapy," said Chelain Goodman, a resident in radiation oncology at NU Medicine and also first author of the study.

The findings are hypothesis-generating, and further studies are needed to validate whether CTC status is actually useful as a predictive biomarker for treatment decisions.

"Before testing for circulating tumor cells can be used in clinic in helping to guide management for our patients with early-stage breast cancer, we need to confirm our findings with a prospective clinical trial," Goodman said. The team is currently in the process of developing such a trial at NU and other institutions.

The study has been published in JAMA Oncology.