Women treated for breast cancer are at higher risk of cancer recurrence if they have dense breasts, according to a new study.
The study's results, published in the Dec. 15, issue of Cancer, indicate that breast cancer patients with dense breasts may benefit from additional therapies following surgery, such as radiation.
Previous studies indicate that women with dense breast tissue are at increased risk of breast cancer. Researchers have suspected that high breast density also may increase the risk of cancer recurrence after lumpectomy, but this theory has not been studied thoroughly.
Researchers at Women's College Research Institute in Toronto reviewed the medical records of 335 patients who had undergone lumpectomy for breast cancer. They monitored the patients for cancer recurrence and compared recurrence with breast density as seen on mammogram, categorized as low density (less than 25 percent dense tissue), intermediate density (25 percent to 50 percent dense tissue) or high density (more than 50 percent dense tissue).
The patients with the highest breast density had a much greater risk of cancer recurrence than did women with the lowest breast density.
Over 10 years, women in the highest breast density category had a 21 percent chance of cancer recurrence, compared with a 5 percent chance among women in the lowest category. The difference in the recurrence rates at 10 years was even more pronounced for women who did not receive radiation. In those women, 40 percent with high-density breast tissue had a recurrence, compared with none of the patients with low density.
"The composition of the breast tissue surrounding the breast cancer is important in predicting whether or not a breast cancer will return after surgery," said Dr. Steven A. Narod, who led the study.
Women with low breast density, who have a low chance of recurrence after surgery, may not need radiation, but women with high breast density could benefit significantly from the additional therapy, the researchers said.