Makers of silicone breast implants have not followed up on thousands of women who received them as required by the Food and Drug Administration as a condition of approval, agency advisers said Wednesday.

Mentor Worldwide and Allergan Incorporated received FDA approval for their silicone gel-filled breast implants in 2006 after agreeing to do large, 10-year post-market studies. But in a two-day meeting to update two FDA panels on the status of those trials, the companies admitted they had lost track of large numbers of women after implantation.

Mentor’s study enrolled more than 40,000 patients but after three years had a follow-up rate of only 21%. Allergan enrolled more than 39,300 women with a follow-up rate of 60% after two years.

Christopher Allman, a spokesperson for Mentor, said since launching the post-approval studies, the company has stressed the importance of follow-up to both the women participating and their doctors. He says it remains a challenge.

“At Mentor’s request, letters from FDA were sent to physicians and patients to encourage follow-up and state the importance of follow-up; unfortunately, there was minimal impact with respect to the follow-up rate,” Allman said. “We continue to encourage women to participate in these studies.

“Typically, it is not standard of care for breast implant patients to visit their plastic surgeon annually. Patients most likely to follow up with their physician are those who experience complications.”

During an open public comment session, some patients and patient advocates told of the horrors they’ve encountered with silicone implants, in some cases imploring the manufacturers to make sure future studies are well-designed and protect women.

Susan Dorsey from Mount Juliet, Tennessee, replaced her saline implants with silicone six years ago and enrolled in Allergan’s study. She said her symptoms began within months.

“I had difficulty raising my arms over my head, I had flu-like symptoms, neck and shoulder pain that resulted in physical therapy three times a week,” Dorsey said. “Blurry vision, tingling, loss of appetite, insomnia, joint pain, anxiety, dizziness. Every day seemed to bring new symptoms.”

Carolyn Wolfe of Virginia had her implants for 28 years and says she had multiple symptoms. Three years ago she was found to have connective tissue disease, chronic fatigue, chronic obstructive pulmonary disease, asthma and irritable bowel syndrome. An MRI revealed 20 lesions on her brain and two collapsed implants with very little silicone left inside. She had them removed.

“Is the FDA willing to publicly state that silicone and platinum leaking into women’s bodies year after year is safe?” she asked panelists.

In contrast, Nicole Noel told the panel she would again get silicone implants after the birth of her second child. “After having two children I had lost all volume. I had no breast tissue. I have more self-confidence and am more proportional.”

Dr. Susan Wood, with George Washington University’s School of Public Health and Health Services, is a longtime champion of women’s health. The former director of policy and program development at the U.S. Department of Health and Human Services’ Office on Women’s Affairs said that unfortunately, time and time again, safety data have come up short.

“For more than 20 years, FDA has been asking manufacturers to conduct and report rigorous studies on the safety and effectiveness of breast implants. This committee is now very aware of the limitations of the current post-approval studies. This leaves us in much the same place as in 2007, or indeed as in 1992,” Wood said. “FDA approved these products by two companies contingent on adequate post-approval studies. These studies do not seem to reach the bar.”

Wood says real enforcement procedures need to be in place, including consideration of withdrawal of approval, requirements for sponsor-funded but independent research conducted for these studies, significant financial penalties, and major labeling or patient information changes.