"In cancer, we create free radical damage to tumor cells with treatment, and we want that, but antioxidants quench this damage, " explains Dr. Brian Lawenda, the clinical director of radiation oncology at the Naval Medical Center, in San Diego, California.

CNN: Antioxidants may interfere with breast cancer treatment

"Partial-breast irradiation is a very promising approach, but there's a lot we have to learn, " says Lori Pierce, professor of radiation oncology at University of Michigan Comprehensive Cancer Center.

WSJ: New Scrutiny for Popular Breast-Cancer Treatment