FDA has issued warning letters to Mentor Worldwide, LLC and Sientra, Inc. related to their silicone gel-filled breast implants for failing to conduct post-approval studies that meet FDA requirements. Any device manufacturer that has an approved silicone breast implant on the market must conduct these studies to evaluate product safety and effectiveness as well as any risks that premarket clinical trials did not answer.

“We’re issuing these warning letters based on the manufacturers’ low recruitment, poor data, and low follow-up rates in their required post-approval studies,” stated FDA Commissioner Scott Gottlieb, M.D. in an FDA news release. “We expect these manufacturers to meet the pre-specified study requirements in order to ensure the collection of long-term data that can be used to inform long-term patient safety. Post-approval studies, along with other surveillance tools such as adverse event reports, registries, and scientific literature, allow the FDA to help ensure the safety of medical devices and protect patients.”

In the warning letter to Mentor, FDA mentioned deficiencies in the company’s post-approval studies for its MemoryShape breast implant: Failure to enroll the required number of patients in the post-approval study, poor follow-up rates, and “significant data inconsistencies.” The agency’s warning letter to Sientra named a “serious deficiency” in the company’s post-approval study for the Silicone Gel Breast Implants and poor follow-up rates with patients (61%).

The warning letters are part of the agency’s commitment made in its Medical Device Safety Action Plan, which was announced late last year.

Mentor and Sientra have 15 working days to respond to the FDA letters and must explain how the violations will be corrected.