FULL PAPER

THERAPEUTIC RESPONSE EVALUATION ON

HYPERTHYROIDISM USING A FIXED DOSED OF I-131

Yulia Kurniawati, and AHS Kartamihardja

Department of Nuclear Medicine, Dr. Hasan Sadikin General Hospital,

Faculty of medicine Universitas Padjadjaran,

Bandung, Indonesia

POSTER PRESENTATION

4th

International Conference on Radiopharmaceutical Therapy

New World Hotel, Ho Chi Minh City, Vietnam

28 Nov – 2 Dec 2011

THERAPEUTIC RESPONSE EVALUATION ON

HYPERTHYROIDISM USING A FIXED DOSED OF I-131

Yulia Kurniawati, and AHS Kartamihardja

Department of Nuclear Medicine, Dr. Hasan Sadikin General Hospital,

Faculty of Medicine Universitas Padjadjaran,

Bandung, Indonesia

Abstract

Introduction.Euthyroidism condition is the ideal expected after treatment of

hyperthyroidism, but there is still no established therapeutical method that can achieve

that condition. Radioactive iodine-131 (131

I) has been used to treat hyperthyroidism for

long time. It is clinically effective, safe, and cost-effective. However, controversy over

the optimum dose of I-131 therapy is still debatable. The aim of this study was to

evaluate the therapeutic response of a fixed dosed I-131 in hyperthyroidism patients.

Material and method. Retrospective study was carried out during January 2010 until

January of 2011. The inclusion criteria were all subjects received I-131 for the first time

with a fixed dose of 8 mCi, diffused and high uptake of Tc-99m. Theraupeutical

response was evaluated based on the patient’s clinical state and or their laboratory

finding3 months after the treatment. Theurapeutical response categorizedgood response

if thyroid hormones within normal limit and/or improvement of clinical state, when

thyroid hormones still high (above normal value ) with improvement of clinical state

was considered as partial response, no respons if there was no changes both on

laboratory finding and clinical state.

Results. There were 127 patients receiving a fixed dose I-131 therapy of 8 mCi during

January 2010 to January 2011. Forty patients did not show a routine examination on

third month.The patients were between 12 to 63 years of age. From the 87 patients,

32(36,78%) were no response, still considered in a hyperthyroid condition, 55 (63.21%)

patients have good responses, which were20 (36.36%) were hypothyroid, 21 (38.18%)

were euthyroid and 14 (25.45%) were partial responses.

Conclusion.Fixed dose I-131 therapyof 8 mCi showed good response in our hospital on

hyperthyroidism, thereforewe can considered as dose of treatment.

Introduction

Hyperthyroidism is a hypermetabolic condition with increased thyroid hormone

production.1,2

Study based on community showed that the incidence of hyperthyroidism

found more in female than male. The prevalence of hyperthyroidism was about 2 % in

female and 0,2% in male.3 A study conducted in UK involving 2.779 people with mean

age was 58 years old showed the incidence of hyperthyroid was 0,8 per 1.000 female

per year.4

The objective of hyperthyroidism treatment is to restore thyroid hormone

level to normal range or euthyroidism.5 Euthyroidism can be achieved by destroyed

thyroid tissue or inhibite synthesis and release of thyroid hormone.1 Destroying thyroid

tissue could be done by surgery or radioiodine ablation and inhibition of synthesis and

release thyroid hormone can be achieved by oral antithyroid drug.1, 2, 6, 7

Recurence hyperthyroid was observed in 34% patients treated with oral anti

thyroid drug. This is the highest among the other treatment modalities. Recurrence

hyperthyroidism after treatment by using I-131 ablation and surgery were 21% and 8%

respectively.8 I-131 now is considered to be drug of choice or second linetreatment

after oral antithyroid drugfor hyperthyroidism patients. However, the optimum dose of

I-131 therapy is still controversy. Until now there was no agreement on dose given for

hyperthyroidism. The dose of I-131 could be given as fixed dose 5-15 mCi based on

empirical study or calculated dose.7,9,10

Calculated dose usually depend on weight of

thyroid gland and I-131 uptake ability of thyroid gland.10,11

The aim of this study was to

evaluate the therapeutic response of a fixed dosed I-131 in hyperthyroidism patients.

Material and method

Retrospective study was carried out during January 2010 until January of 2011 in

Department of Nuclear Medicine, Dr. Hasan Sadikin General Hospital.

Hyperthyroidism patient with diffuse and high uptake thyroid on 99m

Tc- pertechnetate

thyroid scintigraphy were included in this study. Subject was received a single fixed

dose of 8 mCi I-131 for the first time. Therapeutical response was evaluated based on

the patient’s clinical state and or their laboratory finding 3 months after the treatment.

Theurapeutical response categorized as good response is considered if thyroid

hormones within normal limit and/or improvement of clinical state, when thyroid

hormones still high (above normal value) with improvement of clinical state was

considered as partial response, and no respons if there was no changes both on

laboratory finding and clinical state.

Results

Subjects were 127 hyperthyroid patients who received a fixed therapeutic dose of

8 mCi I-131 during period of January 2010 to January 2011 were included in this study.

Out of 127 subjects, 40 subjects were excluded in this study, since they did not show on

the day of a routine follow up 3 months after ablation. Subject who fulfill the study

procedure were 84 consist of 57 female and 27 male. The ages of subject was between

12 to 63 years old (X=36.38 yrs). Subject with history of taking antithyroid drug prior

to radioiodine ablation was 49 (58.33%) and rest of them had no history of taking

antithyroid drug. From the 84 patients, 39 (46.42%) subjects showed good responses,

26 (30.95%) were partial response and 19 (22.61%) were no response. Among subject

with good and partial response (65 subject), there were 20 (36.36%) developed

hypothyroidism, 21 (38.18%) were euthyroid and 14 (25.45%) were partial responses.

Table 1. Therapeutic response based on history of antithyroid drug (n=84)

Characteristi

c

Good

Response

Partial

Response

No

Response

Antithyroid

(+)

19 (22.61%) 18 (21.42%) 12

(14.28%)

Antithyroid (-) 20 (23.80%) 8 (9.52%) 7 (8.33%)

Discussion

The incidence of hyperthyroidism was higher in female particularly in 3rd

to 5th

decade of age.1,3,4

This epidemiological characteristic could explain the number of

female subject (67.85%) was more than male in this study.

Controversy on the use of I-131 for treatment of patient with hyperthyroidism is

not only on the issue who will take advantages of this treatment as first line or second

line, but also there is no established protocol on dose given to the patient. Some

clinicians believe that the goal of radioiodine ablation is to achieve euthyroidism status

as soon as possible and maintain this status as long as possible before come to

hypothyroidism. This group of clinicians usually will give lower dose, bus as

consequences patient will receive serial treatment and take longer time. The other

groups of clinicians believe that all hyperthyroidism patients, particularly grave’s

disease will end with hypothyroidism and the management of hypothyroidism is more

simple and less complication. Due to these reasons, the goal of radioiodine ablation is

to reach hypothyroidism status by using high dose of I-131.5,7

Theoritically, calculated dose is the best choice to treat hyperthyroid, but in fact

calculated dose applied in many department based on weight and thyroid uptatke was

not sufficient. This condition due to the effetiveness of I-131 on hyperthyroid patients

was also influenced by many factors such age, gender, ethnic and history of smoking.

Anti thyroid drug taken prior to radioiodine therapy also could interferen the efficacy of

treatment.1 Due to this situation many center of nuclear medicine used fixed dose of I-

131 ranged 8-15 mCi.1,5,12,13,14

The result from this study showed good and partial response was obseved in 55

(65.47%) subjects. Similar study was done in Bangladesh using fixed dose 8-15 mCi

and the result was 82%,15

This better results could be due to several patients were

recieved higher dose from 8 mCi. The higher the dose of I-131, the faster the

hypothyroidism achieved.1,14

This result was support by other study done in India. The

effectiveness of radioiodine ablation using fixed dose of 5 mCi was less than 59,37%

and in the dose of 10 mCi the effectiveness was 91,22%.14

From 84 subjects, 65

(77.39%) subjects showed good responses and 19 (22.61%) were no response. Among

subject with good and partial response, there were 20 (36.36%) developed

hypothyroidism, 21 (38.18%) were euthyroid and 14 (25.45%) were partial responses.

Leslie et al conclude that fixed dose regimen is simple and as effective as calculated

ones for treatment hyperthyroidism, but they still do not define the ideal fixed dose to

prescribe.11

Subject with history of taking antithyroid drug prior to radioiodine ablation was

49 (58.33%) and rest of them had no history of taking antithyroid drug.1

Although the

impact of preceding antithyroid drug on the outcome of I131

is still debatable, our data

suggest that the drug can reduces the therapeutic efficacy.

Conclusion

Fixed dose I-131 therapy of 8 mCi showed good response in 3 month follow up

for the treatment of hyperthyroidism. Anti thyroid drugs may be a factor that can

reduces efficacy of I-131 on the treatmen of hyperthyroidism.

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