Many low-income women fail to take the hormonal therapy prescribed as part of breast cancer treatment, possibly lowering their survival rates, according to a new study.

"What we found is that many low-income women in North Carolina who might benefit from hormonal therapy are not getting it or are not taking it as prescribed," said Dr. Gretchen Kimmick of the Duke University Medical Center.

Medication that blocks hormones is a key part of treatment for patients who have a type of breast cancer known as hormone receptor-positive. Those tumors grow in the presence of estrogen, and patients are often asked to block the hormone for five years. The therapy helps prevent the recurrence of cancer.

Previous studies have shown that failing to take these drugs is associated with higher mortality rates, Kimmick said in a news release.

The study found that even for insured women with low co-pays for the drugs, 64 percent filled and picked up their prescriptions.

"Our study also shows that in the year following the initial prescription fill, 40 percent of the women were not regularly taking their hormonal therapy," Kimmick said. "Of the women actually taking the pills, 20 percent stopped taking the prescription before the end of the first year. This is alarming since women are even more likely to discontinue use over subsequent years."

The results of the study were published in the May 18 online edition of the Journal of Clinical Oncology.