Dense breasts have less fatty tissue and more non-fatty tissue. Breasts that aren't dense have more fatty tissue and less non-fatty tissue. Mammograms can help you and your doctor determine how dense your breasts are.
A study found the risk of breast cancer coming back (recurrence) after lumpectomy was higher for women with dense breasts compared to women with less dense breasts.
Other research has shown that dense breasts:
- have as much as 6 times higher risk of developing breast cancer
- can make it harder for mammograms to detect cancer; breast cancers (which aren't fatty) are easier to see on a mammogram when surrounded by fatty tissue
In this study, researchers looked at the medical records of 335 women diagnosed with early-stage breast cancer to see if breast density affected recurrence risk. All the women in the study had lumpectomy and most, but not all, also had radiation therapy after lumpectomy to reduce the risk of recurrence. By looking at mammograms done before diagnosis, the researchers determined the density of the breast that later developed cancer.
- 99 women developed cancer in a low-density breast; 3% of these women had a recurrence
- 107 women developed cancer in a medium-density breast; 10.3% of these women had a recurrence -- more than 3 times the rate of recurrence in the low-density group
- 129 women developed cancer in a high-density breast; 15.5% of these women had a recurrence -- more than 5 times the rate of recurrence in the low-density group
Women who had dense breasts and didn't get radiation therapy after lumpectomy were most likely to have a recurrence. This is why many doctors recommend radiation therapy after lumpectomy -- to reduce the risk of recurrence. Based on the results of the study though, the researchers suggested that women diagnosed with early-stage breast cancer in a low-density breast might be able to safely skip radiation therapy after lumpectomy. It's important to know that the safety of this approach hasn't been proven.
The women in the study were followed for different periods of time and didn't all get radiation therapy after lumpectomy, so the researchers used a computer model to predict recurrence risk over 10 years for other women diagnosed with breast cancer based on breast density. The model assumed that all women would get radiation therapy after lumpectomy -- generally the case today. Ten years after diagnosis the estimated risk of recurrence was:
- 5% for cancer in a low-density breast
- 13% for cancer in a medium-density breast -- 3.6 times greater than in a low-density breast
- 21% for cancer in a high-density breast -- 5.7 times greater than in a low-density breast
If you've been diagnosed with early-stage breast cancer, you might want to ask your doctor about the density of your breasts and how this factor might influence your risk of recurrence. Together, you can decide on a treatment plan that makes most sense for you.