Do Breast Implants Affect Breast Cancer Risk?

by Jeffrey Norris The number of women choosing surgical breast implants for cosmetic reasons is skyrocketing, leading researchers and clinicians to wonder whether the implants affect the results of mammography screening and thereby increase a woman's risk of dying from breast cancer. The implants appear as a solid white mass on radiographic film, obscuring some breast tissue. In the first major effort to address this question, researchers - led by UCSF Comprehensive Cancer Center member Karla Kerlikowske, MD, and statistician Diana Miglioretti, PhD, from the Group Health Cooperative's Center for Health Studies in Seattle - used an extensive database containing mammogram results from 1.7 million women. The mammograms were collected from seven regional mammography registries across the United States. The researchers found 137 women with implants who had breast cancer, and matched them by age and other characteristics with 685 women without implants who had breast cancer.

In the United States, plastic surgeons performed 334,052 breast augmentations in 2004. That's up 19 percent from 280,401 in 2003, and more than a tripling from 101,176 in 1997. Breast augmentation is now more popular than nose reshaping, according to these figures, the latest available from the American Society for Aesthetic Plastic Surgery.

The researchers found that screening mammography failed to reveal 55 percent of breast cancers in women with implants, versus 37 percent among women without implants (JAMA, January 28, 2004, pp. 442-450). Although mammography performed worse for women with implants, both failure rates are high. This is because women with implants are younger on average than the greater population of women who undergo screening. Younger women have denser breasts - making tumors harder to see on mammograms - and tumors that occur in younger women commonly grow faster and may become diagnosed clinically after a normal result on a screening mammography examination. Notably, the study revealed that even though more cancers were initially missed, women with implants were not diagnosed with more advanced stages of cancer. "Women who choose to get implants may be more body-conscious and more likely to detect tumors on their own," Kerlikowske speculates. Even though the screening exam does not perform as well for women with implants, mammography still detects many cancers in this group. On the other hand, mammography is not completely accurate for women with or without implants - so a woman who finds a breast lump should call her physician right away, even if she recently has had a mammogram. It already is standard procedure to manipulate the breast and implant during mammography, in an effort to move the implant out of the way, but some breast tissue remains out of view, even on these "implant displacement" images. Miglioretti hopes to launch a new analysis to determine whether the location of breast implants affects mammography outcomes. People also wonder whether the type of implant matters. "Radiologists I talked with said that it should not make any difference whether it is silicone or saline," Miglioretti says. "But I will examine this if we go forward with another study."