Radiological Emergency in Panama
On 22 May 2001, the IAEA informed Contact Points identified under the Convention on Early Notification of a Nuclear Accident ("Early Notification Convention") and the Convention on Assistance in the Case of a Nuclear Accident or Radiological Emergency ("Assistance Convention") of a radiological emergency at the National Oncology Institute in Panama affecting 28 patients undergoing radiotherapy. The emergency involved a radiotherapy unit using a cobalt-60 teletherapy machine and a computerized treatment planning system for calculating the radiation doses to be delivered to patients. The IAEA received a request for assistance from the Panamanian Government under the auspices of the Assistance Convention and you were informed that an expert team was being sent to Panama.
The IAEA team, composed of experts in radiation protection, radiopathology, radiotherapy, radiology and medical physics, from France, Japan, the United States of America and the IAEA, joined by an expert from the Russian Federation representing the World Health Organization, has in the meantime reached preliminary conclusions on the factors contributing to the emergency and the consequences thereof. There is concordance between the findings of the international team of experts and those of national experts.
The team reported that of the 28 affected patients, eight have died, the deaths of five of whom are probably attributable to radiation overexposure. Of the other three deaths, one was considered to have been related to the patient's cancer, while there was insufficient information to draw conclusions with respect to the other two. Of the 20 patients who are alive, some have developed serious radiopathological complications.
The team of experts found that the radiotherapy equipment had been working properly and that it was adequately calibrated. A preliminary assessment of the situation by the team suggests that the apparent cause of the emergency lay with the entering of data into the computer used for the treatment planning system. The computerized treatment planning system used in the National Oncology Institute requires that the data on the spatial co-ordinates of shielding blocks used to protect healthy tissue during radiotherapy be entered into the system one block at a time, following a certain sequence and subject to a limitation on the number of blocks. It is reported that, as from August 2000, the practice used at the National Oncology Institute was changed whereby, in the case of the affected patients, the co-ordinates for all of the blocks were entered as a single block, resulting in incorrect calculated radiation doses and, consequently, treatment times. Together with an apparent lack of written procedures, and of a manual check when the data input procedure was changed, the combination of circumstances resulted in substantial over-exposure to radiation of the patients involved.
The Ministry of Health of Panama has just been briefed by the team on these preliminary conclusions and has agreed that the lessons identified should be shared on an urgent basis with the international community in order to prevent overexposures wherever this configuration of treatment might be in use. While the team's final report has not yet been completed, under the arrangements set out in the Emergency Notification and Assistance Technical Operations Manual (ENATOM), the IAEA is informing Contact Points about the essential facts that have come to its attention surrounding this emergency in order that national authorities and users of computerized treatment planning systems for radiotherapy, including those similar to that involved in this situation, are informed of the unfortunate circumstances that occurred at the National Oncology Institute in Panama. The Contact Points are urged to draw this matter to the attention of the relevant national authorities and users, who are encouraged to check that any relevant systems are being operated in accordance with an appropriate quality assurance programme.