Dense breast tissue raises risk of breast cancer recurrence

By Sheilah Downey

Breast cancer survivors with dense breast tissue have a higher risk of their cancer coming back and could benefit from additional therapies such as radiation, according to a new study.

Researchers also suspect that high breast density also may increase cancer recurrence after lumpectomy, a theory that needs more study, said researchers from the Women's College Research Institute in Toronto.

"The composition of the breast tissue surrounding the breast cancer is important in predicting whether or not breast cancer will return after surgery," said lead author Dr. Steven A. Narod of the Institute.

Dense breast tissue puts women at greater risk for breast cancer for two reasons, according to research. Dense breast tissue shows up as a white mass on a mammogram, as does a tumor, making it harder for a doctor to spot. Additionally, a study in the April issue of Current Biology found that dense breast tissue may encourage growth of more invasive breast cancers.

Authors in the Women's College study said their findings show that women with low breast density my not need radiation after surgery, but women with high breast density could significantly benbefit from the additional therapy, according to the Institute's press release.

Previous studies have already found that women with dense breast tissue have an increased risk of breast cancer, said researchers.

Scientists reviewed the medical records of 335 patients who had undergone lumpectomy for breast cancer. They monitored patients for cancer recurrence and compared those cases with breast density. Low breast density is when the breast consists of less than 25 percent dense tissue, intermediate density is 25 to 50 percent dense tissue and high density is composed of greater than 50 percent dense tissue.

Researchers found that patients with the highest breast density had a much greater risk of cancer recurrence than women with the lowest breast density.

Specifically the study revealed that over a ten year period women with the highest breast densities had a 21 percent chance of cancer recurrence, compared to a 5 percent chance among women in the lowest category.

Cancer recurrence rates after a ten year period were more pronounced for women who did not receive radiation, said researchers. Cancer recurrence shot up to 40 percent in the high-density breast tissue for women who did not receive radiation therapy compared to none of the patients with a low density.

The study was published in the Dec. 15 issue of Cancer, a peer-reviewed journal of the American Cancer Society.