Black women have almost twice the rate of advanced breast cancer as white women do, largely because the disease is often diagnosed after it has already progressed. In addition, some black women have misconceptions about cancer and are reluctant to seek medical help, the researchers said.

"We found in this study on locally advanced breast cancer, mainly done in black women, that almost a quarter of the patients [refused] chemotherapy and radiation therapy that are the standard of care for stage 3 breast cancer," said lead researcher Dr. Monica Rizzo, an assistant professor of surgery in the Division of Surgical Oncology at Emory University School of Medicine in Atlanta.

Why these women balk at treatment is unclear, Rizzo said. "We looked at martial status, as well as religious background, of those women and, unfortunately, we were not able to find any clear identifier," she said.

Things that may be associated with their refusal of treatment are fear of the medical system and poverty, which makes it difficult to get to the hospital and get time off work for treatment, Rizzo said. In addition, cultural differences may also play a role, she said.

Rizzo noted many more blacks refuse breast cancer treatment than women from other populations.