Researchers at the UCLA Department of Radiation Oncology at UCLA's Jonsson Comprehensive Cancer Center report for the first time that radiation treatment, despite killing half of all tumor cells during every treatment, transforms other cancer cells into treatment-resistant breast cancer stem cells. The generating of these breast cancer stem cells counteracts the otherwise highly efficient radiation treatment. Using a unique imaging system they developed to visualize cancer stem cells, the researchers were able to observe the initial generation into induced breast cancer stem cells (iBCSC) in response to the radiation treatment. It was also found that the iBCSC had a more than 30-fold increased ability to form tumors, compared with the non-irradiated breast cancer cells from which they originated. Scientists can uncover the mechanisms and prevent this transformation from occurring, radiation treatment for breast cancer could become even more effective, said study senior author Dr. Frank Pajonk, an associate professor of radiation oncology and Jonsson Cancer Center researcher.