The Chernobyl accident resulted in a number of cases of thyroid cancer in females under the age of 20 y. Many of these individuals were treated with surgical removal of the thyroid gland followed by 131I ablation of residual thyroid tissue. Epidemiologic evidence demonstrates that 131I treatment for thyroid cancer or hyperthyroidism in adult women confers negligible risk of breast cancer. However, comparable data for younger women do not exist. Studies of external radiation exposure indicate that, for radiation exposures of as low as 0.2-0.7 Gy, the risk of breast cancer is greater for infant and adolescent female breast tissues than for adult female breast tissues. METHODS: The effective half-time of 131I measured in athyrotic patients was used together with the OLINDA/EXM computer code to estimate doses to breast tissue in 10-y-old, 15-y-old, and young adult females from ablation treatment. RESULTS: The dose to pediatric and young adult female breast tissue associated with a 5.6-GBq (150 mCi) ablation treatment may range from 0.35 to 0.55 Gy, resulting in a lifetime risk of breast cancer ranging from 2-4 cases per 100 such individuals exposed and a lifetime risk of solid tumors ranging from 8 to 17 solid tumors per 100 such individuals exposed. Administration of multiple ablation treatments, as often occurs with metastases, could result in doses ranging from 0.7 to 1 Gy, with corresponding increases in the lifetime cancer risk. CONCLUSION: These estimates suggest the need for additional research and a possible need for surveillance of young Chernobyl thyroid cancer patients who received 131I ablation treatment.
Cancer risks were studied in 834 thyroid cancer patients given 131I (4,551 MBq, average) and in 1,121 patients treated by other means in Sweden between 1950 and 1975. Record-linkage with the Swedish Cancer Register identified 99 new cancers more than 2 years after 131I therapy [standardised incidence ratio (SIR) = 1.43; 95% confidence interval (CI) 1.17-1.75] vs 122 (SIR = 1.19; 95% CI 0.88-1.42) in patients not receiving 131I. In females treated with 131I overall SIR was 1.45 (95% CI 1.14-1.83) and significantly elevated were noted for tumours of the salivary glands, genital organs, kidney and adrenal gland. No elevated risk of a subsequent breast cancer or leukaemia was noted. SIR did not change over time, arguing against a strong radiation effect of 131I. Organs that were estimated to have received more than 1.0 Gy had together a significantly increased risk of a subsequent cancer following 131I treatment (SIR = 2.59; n = 18). A significant trend was seen for increasing activities of 131I with highest risk for patients exposed to greater than or equal to 3,664 MBq (SIR = 1.80; 95% CI 1.20-2.58). No specific cancer or group of cancers could be convincingly linked to high-dose 131I exposures since SIR did not increase after 10 years of observation. However, upper confidence intervals could not exclude levels of risk that would be predicted based on data from the study of atomic bomb survivors. We conclude that the current practice of extrapolating the effects of high-dose exposures to lower-dose situations is unlikely to seriously underestimate radiation hazards for low LET radiation.
There is little information about the individual safety instructions provided by healthcare professionals to patients receiving radioactive iodine (I-131) therapy for the treatment of benign and malignant thyroid disorders or about whether these instructions are consistent across medical specialties. Currently, no national guidelines exist to standardize safety instructions related to I-131 administration. Here, we examine the spectrum of I-131 safety practices in contemporary use.
Members of major societies of physicians and allied specialists who treat patients with thyroid disorders were invited to complete a 27-question online survey about safety practices related to I-131 administration. Data from questionnaires were analyzed by type of safety recommendation and grouped according to provider specialty and geographic location.
A total of 311 endocrinologists, surgeons, nuclear medicine radiologists, and allied health professionals completed questionnaires. They indicated that patients often receive instruction from more than one treating specialist. The decision to hospitalize a patient for treatment and the length of stay were determined by the patient's social situation and the dose of I-131 administered. Starting at I-131 doses between 259 and 1073?MBq (7 and 29?mCi), over 60% of respondents advised avoiding contact with children, sexual activity, and breastfeeding, with the latter recommendation continuing beyond 48 hours after treatment. Personal hygiene, laundry, and meal preparation precautions varied across respondents. Over 90% of respondents used serum or urine testing to screen for pregnancy status. Precautions to delay parenthood were given more often to female than male patients (90% vs. 60%), with a minimum recommended delay of 6 months. About 20% of respondents considered insurance coverage as a factor in selecting outpatient versus inpatient I-131 therapy, and this consideration varied geographically.
A wide variety of safety recommendations are given to patients who receive I-131. To our knowledge, this survey represents the first organized inquiry into safety practices related to I-131 administration. The diversity of responses suggests an opportunity for multispecialty collaboration in defining more uniform recommendations for patient safety instructions during and after I-131 treatment.
Therapeutic application of 131I for the treatment of thyroid cancer generates a significant amount of liquid radioactive waste. Discharge of this waste into the public sewage system is governed by local regulations. In Canada, the permissible concentration is such that only a few patients can be treated in modern water-efficient buildings if this waste is discharged directly through the toilet to the public sewage system. If the toilet discharge is first collected into a holding tank for physical decay before it is released, a large patient load can be handled without exceeding the permissible concentration. In this paper, the principles of operation and the design parameters are discussed, and a multiple holding tank system installed in the Princess Margaret Hospital/Ontario Cancer Institute is described.
To identify regional differences in recommendations for radioactive iodine remnant ablation (RRA) in early stage well-differentiated thyroid carcinoma (WDTC) within Canada and the United States.
A cross-sectional written survey of a sample of physicians in specialties potentially involved in thyroid cancer care was performed in 2006. Participants were asked if they recommended RRA for a hypothetical 38-year-old woman with a solitary, 1.6-cm papillary carcinoma resected by total thyroidectomy. Exploratory regional comparisons were performed using Student t tests or analysis of variance. The regions studied were western Canada, eastern Canada (Ontario, the Maritimes), Quebec, the northeastern United States, the western and midwestern United States, and the southern United States. In a secondary multivariable logistic regression analysis, we explored potential relationships between individual respondent characteristics RRA recommendations.
Agreement with case-based RRA recommendations was measured on a Likert scale of 1 to 7 (7 = strongest agreement).
The effective response rate was 56.3% (486/864). There were significant differences in RRA recommendations among the regions studied (F = 11.99, 5 df, p
A case-control study of Swedish thyroid cancer patients was conducted to evaluate the possible influence of 131I treatment and external radiotherapy on the risk of developing a subsequent cancer. Both cases and controls derived from a cohort of Swedish thyroid cancer patients treated with 131I (n = 834) or by other means (n = 1,121). Thirty-six breast, 13 stomach, 12 kidney, and 5 bladder cancers were found more than 2 years after 131I treatment/thyroid cancer diagnosis. Individual, absorbed dose in the organs was calculated by using ICRP tables, administered activity of 131I, and 24-h 131I uptake. In studying the effect of 131I and external radiotherapy no statistically significant dose-response relationships were found for cancers of the breast, stomach, bladder or kidney. When the absorbed dose from 131I was analyzed separately the risks remained essentially the same. The present follow-up time and the relatively low absorbed dose that the patients received from 131I and external radiotherapy necessitate studies with a longer follow-up time or a larger patient material before more firm conclusions can be made.