The following information was provided by the licensee via phone and email:
On 6/12/25 four patients received intradermal administrations of 3 mCi Tc-99m mebrofenin (in three 1-mCi injections at the site) instead of the prescribed 3 mCi Tc-99m sulfur colloid (in three 1-mCi injections at the site) for sentinel lymph node biopsy.
A physician detected an abnormality on imaging. One patient was also administered the correct (prescribed) dose of 3 mCi Tc-99m sulfur colloid before going to surgery. The other three patients had already gone to surgery when the abnormality was detected. The surgeon detected lymph node counts for two of the patients and resected the nodes (assumed successfully). The surgical status of the third patient is unknown; nuclear medicine will review the pathology results for all four patients when available and follow up accordingly.
Since 6/12/25, nuclear medicine has been investigating the circumstances that led to dispensing an administration of the wrong radiopharmaceutical and evaluating the dosimetry implications of mebrofenin. Because mebrofenin is typically administered intravenously for liver and gallbladder studies, there is little or no published information on skin dose from intradermal administration. The authorized medical physicist (AMP) does not believe the shallow-dose equivalent (SDE) from 3 mCi intradermal mebrofenin would exceed the documented SDE from 3 mCi intradermal sulfur colloid (105 rad) due to the biokinetics of mebrofenin. Imaging suggests that it quickly migrated away from the injection site. However, on 6/19/25, the radiation safety officer (RSO), in consultation with nuclear medicine and the AMP concluded that the event should be reported to NRC as a potential medical event, because we cannot be certain that the SDE does not exceed 50 rad.
All patients and their referring physicians have been notified. The authorized user physician does not expect any adverse effects as a result of the dosing error.
The RSO will contact REAC/TS to determine if an accurate SDE can be calculated or derived for this event.
The licensee notified the NRC Region 3 project manager.
The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
A Medical Event may indicate potential problems in a medical facility's use of radioactive materials. It does not necessarily result in harm to the patient.