Quarterly assessment of radiotherapy events, classified as level 1 on the ASN-SFRO scale, reported between 1 January and 31 March 2010

 Twenty events, classified as level 1 on the ASN-SFRO scale, were reported between 1 January and 31 March 2010. Although these events are not expected to have any impact on patients' health, they are analysed to see if any lessons can be learnt from them (particularly in terms of organisation) and to avoid any recurrence.

Each event reported concerned only one patient.

Thirteen of the events concerned patient positioning errors as follows:

 * wrong side treated;

 * failure to detect error in patient's position on the control image at the start of treatment;

 * wrong reference image used;

 * in six patients receiving treatment involving the irradiation of two regions, an error occurred during the selection of one of the regions, with the result that the first region was irradiated with the beams intended for the second; these events occurred at five different centres;

 * three events in which an incorrect offset was applied to the reference point used in identifying the target area; this concerned two sessions in one case, and a single session for the other two;

 * patient's position reversed (in the head-to-foot direction) during two sessions.

A single radiotherapy session was concerned for the first nine events mentioned above.

Five events concerned the administration of an inappropriate dose, caused by:

 * three cases of mistaken identity concerning patients receiving treatment in the same part of the body: these events occurred at three different centres;

 * one data input error concerning the beam energy level;

 * in the case of a treatment with two target volumes, one of the volumes received two unnecessary treatment sessions.

A single radiotherapy session was concerned for each of the first three events mentioned above.

Two events concerned a beam shaping error due to:

 * a collimator aiming error (the collimator is the part of the accelerator used to size the treatment beam), with the result that two treatment beams overlapped on a small area during eleven sessions;

 * wrong personalised mask selected for one beam during a session.

ASN investigates level-1 events during specific inspections and during its regular inspections of radiotherapy centres. After analysing the event, it systematically examines all the corrective measures proposed at each centre.

Corrective measures for the period concerned here included modifying the patient identification procedure and raising personnel awareness of the importance checking the patient's position.

At some centres where an event had been reported, a procedure was set up for radiotherapy technicians to double-check patient position and to take systematic daily control images for patients whose treatment involves multiple target areas.