Measurement of Radiation Exposure in Relatives of Thyroid Cancer Patients Treated With 131I

Abstract

This work evaluates the radiological risk that patients treated with I for differentiated thyroid cancer could present to relatives and occupationally exposed workers. Recently, the International Atomic Energy Agency issued document K9010241, which recommends that patient discharge from the hospital must be based on the particular status of each patient. This work measures effective dose received by caregivers of patients treated with I at the Instituto Nacional de Cancerología, Mexico City. Thermoluminescent dosimeters were carried during a 15-d period by 40 family caregivers after patient release from hospital. Relatives were classified into two groups, ambulatory and hospitalized, according to the release mode of the patient, and three categories according to the individual patient home and transport facilities. Categories A, B, and C were defined going from most to least adequate concerning public exposure risk. Measurements were performed for 20 family caregivers in each group. The effective dose received by all caregivers participating in this study was found to be less than 5 mSv, the recommended limit per event for caregivers suggested by ICRP 103. In addition, 70 and 90% of ambulatory and hospitalized groups, respectively, received doses lower than 1 mSv. Caregivers belonging to category C, with home situations that are not appropriate for immediate release, received the highest average doses; i.e., 2.2 ± 1.3 and 3.1 ± 1.0 mSv for hospitalized and ambulatory patients, respectively. Results of this work have shown that the proper implementation of radiation protection instructions for relatives and patients can reduce significantly the risk that differentiated thyroid cancer patients treated with I can represent for surrounding individuals. The results also stress the relevance of the patient's particular lifestyle and transport conditions as the prevailing factors related to the dose received by the caregiver. Therefore, the patient's status should be the criterion used to decide his/her release modality. This work provides support to recommend the implementation of the "patient specific release criteria" in accordance with ICRP 94, IAEA Safety Report No. 63, and IAE document K9010241 A for patients treated with radiopharmaceuticals.

Patient hospitalisation for radionuclide therapy should be the exception and not the norm

“…On this topic, the literature has an abundance of highquality studies which show that in almost all cases, the radiation dose to members of the patient's family is far less than whatever constraint is imposed. Similar studies have been conducted in the USA [3,4], Belgium [5,6] and Mexico [7]. In this series of studies which looked at the radiation dose to family members of thyroid cancer patients after radioactive iodine was administered, out of 219 family members who were monitored, only 14 (6%) exceeded the constraint of 1 mSv.…”

“…This would suggest that the hospitalisation protocol used by the institution was not the critical difference. Research has shown that the significant difference is between those who have excellent facilities for isolating at home and those who have very poor facilities for isolating at home [7,8]. In fact, when Iodine was administered as an outpatient procedure it was almost always possible to fit within the constraints required and this was especially the case in more developed countries [4,7].…”

“…We can reference numerous papers stating that outpatient therapy treatments can be 'successfully' undertaken, and my colleague has done this admirably. However, one of the salient points that I glean from such papers [4,7,11,12] is that, yes, outpatient therapies may be undertaken successfully but often there is a caveat detailing some general conditions relating to compliance with radiation safety procedures and guidelines. There is an assumption that such guidelines and procedures are available, in place and/or observed [4,7,11,12].…”

Diseño de un modelo para la estimación de la dosis recibida por los colectivos cercanos a los pacientes sometidos a tratamiento de restos de Ca. de tiroides con I-131.

“…El cáncer diferenciado de tiroides (CDT) es la enfermedad endocrina de diagnóstico más habitual (98%), 1 aunque es un tumor poco frecuente al representar un porcentaje muy pequeño del total de cánceres detectados a nivel mundial (< 1.5%). Las expectativas del paciente, tras un tratamiento adecuado, son excelentes alcanzando tasas de supervivencia del 97% a los 5 años.…”

“…Éste se encuentra en estado metaestable y se desexcita con la emisión de radiación gamma con energía 364 KeV. 1,4 La emisión de radiación gamma además del porcentaje de eliminación del radionúclido a través de la orina son las razones para tener que tomar medidas de protección radiológica tras la administración del radionucleido en la terapia metabólica. 5 Por ello, se ingresa al paciente en una habitación blindada con el WC conectado a un depósito especialmente preparado para recoger los excrementos en un área adecuada, lo que permite, además de la recogida controlada de la mayor parte del isotopo radiactivo eliminado por el paciente, la minimización de la exposición de los diferentes colectivos con riesgo de irradiación, particularmente el del personal sanitario y el del entorno más próximo al paciente.…”