A new study developed by the University of California at San Francisco suggests that women who have dense breasts are at a higher risk to develop breast cancer than others.
Women who have a lower risk than those with denser breasts include the ones with breast cancer history in their family, with previous benign breast tumors, or those who had their first pregnancy over the age of 30.
The study appeared on Thursday in the journal JAMA Oncology and is probably the first large-scale research to link breast density to the risk of developing breast cancer. It found that about 40 percent of women aged over 40 have dense breast tissue. The density makes it harder for the cancer cells to be identified on a mammogram.
This made 27 states to pass laws that require the doctors to tell women when they have dense breast tissue. Afterwards, they can decide if they want to undergo further screening procedures, like ultrasound or MRI. However, the critics of this law think that this may cause unnecessary fears to women, since it is not always the case that they need further screenings.
The study analyzed about 200,000 women with ages from 40 to 74 and evaluated the potential risks they had to develop breast cancer. The results showed that around 18,000 participants had malignant breast tumors, while the others were healthy.
Therefore, they found that the predominant risk factor is breast density. Also, 39.3 percent of the cases of breast cancer in premenopausal women and 26.2 percent of cases in postmenopausal women could have been prevented if the density of their breasts had been lowered.
Although age is an important factor that determines breast density, it appears that women with a high body mass index have breasts that are lower in density. Thus, dense breasts are more common among younger women and they experience a decline in density starting with the menopause.
Tamoxifen is an estrogen hormone blocker that is one of the few treatments that substantially reduces breast density. However, it may cause side effects and it should be taken only at the doctor’s advice and in a high risk of breast cancer.
The study suggests that other measures should be found to reduce density and, thus, breast cancer can be prevented rather than treated.
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