The following information was received from the State via e-mail:
The two reported cases are single channel MammoSite patients. The errors resulted from erroneously placing the dwell position approximately 2 to 2.5 cm proximal to the correct position. The error was not noticed until 2/14/10 during a document review for [the second] patient after [the eighth] fraction. The last two fractions for [the second] patient were corrected. It appears that about 50% of the correct treatment volume received at least 50% of the prescribed dose. Some parts of the planned volume received greater than 700%. Also there are volumes that are not included in the planned treatment volume that exceed approximately 300% to 400% of the prescribed dose. The proximal skin received a small sliver of dose at the 125% the prescribed dose.
First patient's treatment had been completed in January before the error was noticed. Probably 25% of the planned volume received the prescribed dose or higher. Probably 25% of the planned volume received 25% or less than of the prescribed dose. A large volume outside the planned treatment volume exceeded the prescribed dose. The maximum proximal skin dose was at approximately 220% of the prescribed dose. The desired dose was 340 cGy/fx * 10. Both doctors and patients have been notified.
Health effects, if any, are still being determined. The licensee will send a written report on this incident.
The State of Florida is investigating. The isotope involved is 9.76 Curies of Ir-192.
Florida Incident Number: FL 10-027.
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.