Breast implants reduce the amount of tissue visible in mammograms by up to one-half in women whose breasts have a lot of scar tissue, researchers have reported.
Such women make up 10 percent to 20 percent of the 1.5-million or more recipients of breast implants since the early 1960s, said Dr. Neal Handel, a plastic and reconstructive surgeon who wrote the study published in Wednesday's issue of The Journal of the American Medical Association.
Implants have been known to increase the difficulty of seeing breast tissue in cancer-screening X-rays, but this study is the first to determine by how much, Handel said.
It is also the first to show that implants increase tissue visibility in the 10 percent of women with the smallest natural breasts, Handel said.
Mammograms are one of the best screening tools for breast cancer, expected to develop in one of 10 American women. Mammograms can show tiny malignancies years before they can be felt by hand, greatly increasing the likelihood of catching tumors before they spread.
Researchers compared mammograms on 68 women before and after they had breast implants at the private clinic where Handel practices in Van Nuys, Calif. Findings were presented at a conference Tuesday in Marina del Rey, Calif.
The greatest factor in reducing visibility was the amount of scar tissue around the implants, researchers said. Women with little scar tissue had about a 30 percent reduction in visibility. That rose to about 50 percent in women with moderate to severe scarring, the study found.
"They should consider doing something about it _ removing the implants or getting a correction," Handel said Monday by telephone. "It can be corrected, though the correction doesn't always last."
A method called the Eklund technique, designed to improve mammograms in women with implants, increased the visibility of breast tissue only about 5 percent, the study said.
Dr. Peter Jokich, director of breast imaging at Rush-Presbyterian-St. Luke's Medical Center in Chicago, said the study is hampered because mammography temporarily compresses breast tissue, casting doubt on estimates of the tissue visualized.
"A lot of conclusions they reach are logical conclusions," Jokich added. "A lot are common-sense conclusions you'd reach without a study like this."
Handel said it isn't possible to estimate how many cancers might be missed because of implants. He added the procedure remains "within the realm of acceptable risk, considering the benefits."
The researchers studied only silicone implants, not saline-filled.