Long‐term Follow‐up of Hyperthyroid Cats Treated With Iodine‐131

Slater, Margaret R.; Komkov, A.; Robinson, Laura E.; Hightower, D

doi:10.1111/j.1740-8261.1994.tb01594.x

Cited by 41 publications

(46 citation statements)

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“…After the 1-hour image, cats were placed in a ward designated as a holding area for animals after radionuclide imaging procedures and handled in accordance with standard radiologic safety requirements in existence at the time of the scan. 6 Iodine 131 as sodium iodide d was injected into a peripheral vein to achieve thyroid ablation. Cats typically were unsedated and minimally restrained during injection.…”

Section: Subject Selectionmentioning

confidence: 99%

“…Short-term information about the cats in this article has been published previously. 6 The ability to provide owners with information about expected life span of an older cat with hyperthyroidism would be valuable. The objectives of this study were to examine the survival of a cohort of older, hyperthyroid-treated cats based on data available at the time of diagnosis of hyperthyroidism to provide numerical estimates of expected survival for use in decision-making at the time of diagnosis; and to describe the age and common health problems at time of death as well as assess the association of factors From the Departments of Veterinary Anatomy and Public Health (Slater, Geller)…”

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Long-Term Health and Predictors of Survival for Hyperthyroid Cats Treated with Iodine 131

2001

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Two hundred thirty-one cats treated with radioactive iodine at the Texas Veterinary Medical Teaching Hospital were followed for a median of 25 months by means of an ambidirectional (prospective, retrospective) cohort study design. Cox proportional hazards models were used to determine predictors of survival based on data at the time of hyperthyroid diagnosis (collected retrospectively) and found that only age at diagnosis and sex of the cat were predictors of survival. Increasing age (for each year of age, relative risk [RR] ϭ 1.2, 95% confidence interval [CI] ϭ 1.1-1.3) and being male (RR ϭ 0.68, 95% CI ϭ 0.5-0.9) increased likelihood of death. Tables predicting survival after diagnosis and treatment of hyperthyroidism for various age and sex combinations were created. In addition, Cox proportional hazard models were run with all data available at the end of the study (collected retrospectively and prospectively) including number and type of major health problems reported at the time of death or censoring. In this model, significant factors were age at diagnosis, sex, and either type of major health problem or number of health problems. Cats with renal disease or cancer were more likely not to survive and increasing from none to 2 health problems also decreased survival. Renal problems and cancer were the most common health problems at the time of death or censoring. This study provides estimates of duration of survival for cats successfully treated for hyperthyroidism with radioactive iodine, which can be useful in assisting with client treatment decisions.Key words: Cancer; Renal disease; Survival analysis.C ats have recently become the most popular pet in the United States, 1 and are increasingly well cared for with improved nutrition and more frequent veterinary care. Little is known about the life expectancy and most common causes of death of this population of well-cared-for pet cats. Existing references with survival data are outdated or use age at postmortem examination at a referral hospital, neither of which provide accurate clinical information in the subpopulation of well-cared-for pet cats with hyperthyroidism. 2,3 Long-term survival of cats that are already old enough to develop old-age-related health problems such as hyperthyroidism is unknown. Two articles report survival in a longer-term context, the 1st with a mean of 13 months of follow-up after treatment and the 2nd with a median follow-up period of 24 months. 4,5 The primary focus of these articles was short-term treatment success of hyperthyroidism. Short-term information about the cats in this article has been published previously. 6 The ability to provide owners with information about expected life span of an older cat with hyperthyroidism would be valuable. The objectives of this study were to examine the survival of a cohort of older, hyperthyroid-treated cats based on data available at the time of diagnosis of hyperthyroidism to provide numerical estimates of expected survival for use in decision-making at the time of diagnosis; and t...

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Long-Term Health and Predictors of Survival for Hyperthyroid Cats Treated with Iodine 131

2001

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“…Sodium iodide solution containing 74-333 MBq of free, no-carrier-added 131 I is delivered into the feline body, usually by subcutaneous injection (Slater et al 1994;Feeney and Anderson 2007). A large fraction of administered activity is absorbed into thyroid tissues shortly after intake.…”

Section: Introductionmentioning

confidence: 99%

Correlation Between Exposure Rate and Residual Activity in Felines Undergoing 131I Thyroid Ablation Therapy

Martin

Vasudevan

Chirayath³

2015

Health Physics

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Radioiodine thyroid ablation therapy is a common method for treatment of felines exhibiting hyperthyroidism. Due to the high gamma-ray emission rate of radioiodine (I), patients following treatment must be held in isolation for several days before release to prevent unnecessary dose to owners and members of the public. Dose rate measurement on the external surface of the patient of ≤ 20 μSv h is maintained as the patient release criterion without regard to residual activity. However, the Texas Department of State Health Services regulatory guide recommends a release limit of 3.7 MBq to households with non-pregnant women and children over the age of 18 y, and a limit of 925 kBq to households of pregnant women and children who can be supervised. In this paper, Monte Carlo computational radiation transport techniques are employed to predict and standardize the patient isolation time at the clinic by correlating the thyroid burden and surface dose rates of felines. Measurements of patient dose rate as a function of time are used to determine the patient-specific effective half-life experimentally and to validate the model results. Results show that an average holding time of 8 to 9 d is sufficient to reduce the residual activity to 3.7 MBq levels. Additionally, contact dose rate measurements of 20 μSv h or less correlate to residual activity levels of approximately 925 kBq. Based on the model and measurements, a protocol was developed for clinical use at Texas A&M University Veterinary Medical Teaching Hospital to allow estimation of residual activity following injection. This in turn confirms that the surface dose rates used as the release criteria follow the release limits recommended in the regulatory guide.

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“…3 Radioiodine is regarded as the gold standard treatment, with advantages including: (i) potential for curative treatment, with approximately 94% of cats cured following a single treatment, 4 (ii) efficacy independent of location and type of hyperfunctional thyroid tissue, (iii) longer median survival compared to cats treated with anti-thyroid drugs, (iv) superior cost effectiveness for cats surviving beyond one year following diagnosis compared with anti-thyroid drugs and (v) safety, with minimal adverse effects and no requirement for general anaesthesia or even sedation in most instances. [4][5][6][7][8] However, restricted accessibility and requirement for hospitalisation can represent potential barriers to radioiodine use. 7,9 Curative success of thyroidectomy is dependent on the location of hyperfunctional thyroid tissue, which is important as ectopic hyperfunctional thyroid has been reported in 4 to 23% of hyperthyroid cats.…”

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confidence: 99%

Management and monitoring of hyperthyroid cats: a survey of Australian veterinarians

Kopecny¹,

Higgs

Hibbert

et al. 2016

Journal of Feline Medicine and Surgery

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Method:An invitation to complete an online survey was sent to veterinarians in all states and territories of Australia. The survey comprised questions relating to management of hyperthyroidism, use of anti-thyroid drugs v radioiodine treatment v surgical thyroidectomy, in addition to demographic information for respondents. Results:A total of 546 clinicians completed the survey. The most commonly preferred treatments for long-term management of feline hyperthyroidism were anti-thyroid medications (305/546; 56%) and radioiodine (210/546; 38%), with substantially more respondents selecting radioiodine when cost was removed as a consideration (425/546; 78%). However, most respondents had treated or referred few cases for radioiodine (median 2). Most veterinarians (500/546; 92%) used anti-thyroid medications either long-term or prior to definitive treatment of hyperthyroidism. For medical management, 45% (244/546) of veterinarians used twice daily carbimazole. Half of respondents (274/546) aimed to 3 maintain the total T4 concentration anywhere within the laboratory reference interval (RI) in hyperthyroid cats without chronic kidney disease. Blood pressure monitoring was uncommon. Surgical thyroidectomy was rarely performed. Conclusions:Radioiodine was more frequently preferred by Australian veterinarians compared to those in the UK, likely associated with greater availability, reduced cost and shorter hospitalisation times in this jurisdiction, though anti-thyroid medications were the most frequently used treatment modality. Barriers remain to its utilisation, however, including perceived cost, misconceptions with regard to expected success rate and accessibility. Recent changes to recommendations on the management and monitoring of hyperthyroid cats do not appear to have been widely adopted by veterinarians at this time.

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Long‐term Follow‐up of Hyperthyroid Cats Treated With Iodine‐131

Cited by 41 publications

References 3 publications

Long-Term Health and Predictors of Survival for Hyperthyroid Cats Treated with Iodine 131

Long-Term Health and Predictors of Survival for Hyperthyroid Cats Treated with Iodine 131

Correlation Between Exposure Rate and Residual Activity in Felines Undergoing 131I Thyroid Ablation Therapy

Management and monitoring of hyperthyroid cats: a survey of Australian veterinarians

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