Zaragoza Radiotherapy Accident

Walter Goodwin
March 25, 2017

Submitted as coursework for PH241, Stanford University, Winter 2017


Fig. 1: A modern example of a linear accelerator used for radiotherapy. (Source: Wikimedia Commons)

Since the advent of radiation, accidents involving radiation damage have been rare and have had a very low reproducibility rate. The causes and severity of these accidents vary greatly. In some cases, the radiation source is identified and the exposed individuals do not experience adverse effects, while in other cases the accident goes unnoticed until injuries appear [1]. In medical practice, radiotherapy can lead to "accidental overirradiation syndrome," which is the result of very high doses of irradiation to the organs. In this situation, symptoms do not instantly appear even in the case of much higher than normal doses of irradiation [2].

The Accident

In December 1990, a malfunction of the electron linear accelerator (see Fig. 1) in the Clinic of Zaragoza led to irradiation of 36 MeV, which was the highest beam energy. In this accident, 27 patients, who were supposed to receive much lower energies, received doses up to seven times higher in their targeted regions. These treatments targeted the cervical region, chest wall, inguinal region, trapezius muscle area, dorsal region, frontal lobe, and mammary nodes. Due to the high dose, many of the patient experienced negative symptoms, with the earliest symptoms becoming present six days after their final radiotherapy session [2].

The first visual symptom presented by the overirradiated patients was radiodermatitis, which occurred in all but one patient. Within the first month after the beginning of treatment, other symptoms became apparent, such as dysphagia and changes to intestinal transit. However, as time continued to pass, it became apparent that patients had damage to many organs, including the esophagus, oropharynx, lungs, cervical cord, liver, colon, stomach, and skin. Although treatment was used in an attempt to cure these patients, 20 of the 27 died within three years, three of which dying from causes unrelated to the overiraddiation [2].

Lessons Learned

In the case of the 1990 Clinic of Zaragoza radiotherapy accident, it is evident the incident could have been prevented by proper calibration and maintenance of the equipment. This is the case with the reported accidents with the most severe consequences because a mistake in calibration may not be promptly discovered. Historically, these types of mistakes have been due to insufficient training of the medical staff, lack of quality assurance, and misunderstanding the implications of imprecise adjustments of the equipment. Therefore, it is important that written procedures and protocols are put in place for new radiotherapy equipment, as well as a quality assurance program [3]. Although the accidents of the past are unfortunate, we can learn many lessons from them. Moving forward, it is critical that we attend to the deficits within radiotherapy in order to improve patient safety and confidence.

© Walter Goodwin. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] J. Nénot, "Radiation Accidents Over the Last 60 Years," J. Radiol. Prot. 29, 3, 301 (2009).

[2] R. Escó et al., "Accidental Overirradiation Syndrome," Radiother. Oncol., 28, 2, 177 (1993).

[3] Lessons Learning from Accidents in Industrial Radiography (International Atomic Energy Agency, 1998).