Assessing efficacy of radioactive Iodine treatment for differentiated thyroid cancer

The purpose of the audit is to evaluate the efficacy of post-surgical thyroid ablation for differentiated thyroid cancer (DTC) following first ablative dose.

In patients with local disease, post-thyroidectomy radioactive iodine treatment (RAIT) is routinely offered to patients with DTC >1cm in size on histological examination and has been shown to reduce the risk of local and distant recurrence and death from thyroid cancer [1-3].

In accordance with British Thyroid Association guidelines, a post-treatment whole body scan (WBS) is performed followed by a diagnostic Iodine-123 scan four to six months post therapy to assess effectiveness of treatment. If no residual uptake is seen in the thyroid bed then patients receive long term follow-up. However, if persistent uptake is demonstrated, a second treatment is offered.

In a proportion of patients, multiple treatments are needed to achieve complete ablation. With increased exposure to radioactive iodine come several disadvantages such as increased risk of second cancer, increased cost with longer hospital stays and more prolonged symptoms of hypothyroidism with thyroid hormone withdrawal prior to and during each treatment and scans [4].

It has been reported that the amount of remnant thyroid tissue correlates with uptake on post-treatment WBS [5]. Recent preliminary results from two randomised controlled trials looking at radioiodine dose showed high efficacy rates of up to 95% from the first ablative dose in low risk DTC [6,7]. This audit assesses the efficacy of post-surgical thyroid ablation.

The standard: 

In the post-operative treatment of DTC, successful ablation of remnant thyroid tissue should be achieved in the majority of patients following a single treatment of radioactive Iodine-131.

Target: 

87% [8]

Indicators: 

The proportion of patients with DTC where the first ablative dose had been successful in ablating remnant tissue.

Data items to be collected: 

• Histology

• Percentage uptake on post-treatment WBS

• Number of RAIT

Suggested number: 

50 consecutive patients.

• Identify reasons for target not being met. Unsuccessful ablation following a single dose may be due to a high amount of remnant tissue post-thyroidectomy. The amount of remnant tissue may be reduced with a more complete surgery. This can be explored further by stratification of data by surgeon or DGH versus tertiary referral centre. Potential solutions include audit of surgical performance and centralisation to allow for specialist surgeons to perform the procedure

• Another reason might be due to a high proportion of patients having high-risk/radio-resistant tumour – hurtle cells, R1 margin, node positive. Standard may need to be adjusted at a departmental level depending on the prevalence of such tumour types in the local patient population

• Re-audit in 12 months

Access to patients notes with treatment records, imaging and histology.

1. British Thyroid Associations Guidelines for the management of thyroid cancer. Second ed. London: Royal College of Physicians; 2007

2. Verburg FA, de Keizer B, Lips CJ, Zelissen PM, de Klerk JM. Prognostic significance of successful ablation with radioiodine of differentiated thyroid cancer patients. Eur J Endocrinol 2005; 152(1): 33-7.

3. Sawka AM, Thephamongkhol K, Brouwers M, Thabane L, Browman G, Gerstein HC. Clinical review 170: A systematic review and metaanalysis of the effectiveness of radioactive iodine remnant ablation for well-differentiated thyroid cancer. J Clin Endocrinol Metab 2004; 89(8): 3668-76.

4. Rubino C, de Vathaire F, Dottorini ME, Hall P, Schvartz C, Couette JE, et al. Second primary malignancies in thyroid cancer patients. Br J Cancer 2003; 89(9): 1638-44.

5. Samuel AM, Rajashekharrao B. Radioiodine therapy for well-differentiated thyroid cancer: a quantitative dosimetric evaluation for remnant thyroid ablation after surgery. J Nucl Med 1994; 35(12): 1944-50.

6. Mallick U. (OC-068) HILO: multicentre randomised phase iii clinical trial of high vs low dose radioiodine, with or without recombinant human thyroid stimulating hormone (rhTSH), for remnant ablation for differentiated thyroid cancer.[dissertation]. Paris, France.: 14th International Thyroid Congress; 2010.

7. Catargi B, Borget I, Deandreis D, Zerdoud S, Bridji B, Bardet S, et al. (OC-067) Comparison of four strategies of radioiodine ablation in patients with thyroid cancer with low-risk of recurrence: the randomized, prospective ESTIMABL study on 753 patients.[dissertation]. Paris, France.: 14th International Thyroid Congress; 2010.

8. Sirisalipoch S, Buachum V, Pasawang P, Tepmongkol S. Prospective randomised trial for the evaluation of the efficacy of low vs high dose I-131 for postoperative remnant ablation in differentiated thyroid cancer. World J Nuclear Med 2004; 3(Supp 1): S36.

S Teoh, J Statham, A Weaver