No adverse affect in clinical outcome using low preablation diagnostic (131)i activity in differentiated thyroid cancer: refuting thyroid-stunning effect.
BACKGROUND
Published studies of thyroid stunning due to preablation (131)I scanning in the treatment of differentiated thyroid cancer after thyroidectomy had shown inconsistent clinical impact.


OBJECTIVE
The objective of the study was to evaluate the clinical outcome in patients who were given a low diagnostic (131)I activity (1.1 mCi or 40 MBq) 6 days prior to radioiodine ablation (RAI).


METHODS
Two cohorts of patients were treated in a cancer referral center in 2004-2011. The eligibility criteria were as follows: 1) diagnosis of differentiated thyroid cancer; 2) total or near total thyroidectomy; 3) no distant metastasis; and 4) receiving 82.4 mCi or greater (3050 MBq) therapeutic (131)I activity.


METHODS
Three hundred five consecutive patients treated in 2004-2008 (group A) had a diagnostic activity 1.1 mCi of (131)I prior to RAI. The second cohort treated in 2009-2011 (group B) consisted of 237 patients who did not undergo diagnostic (131)I scanning prior to RAI.


METHODS
The tumor recurrence rate at 3 years and quantitative assessment using diagnostic whole-body radioiodine scans and TSH-stimulated thyroglobulin levels at 3-12 months after RAI were measured.


RESULTS
The 3-year recurrence-free survival rates were 96.4% in both groups, with 4.3% in group A and 3.4% in group B having tumor recurrence (P = .91). The ablation success rates measured by diagnostic whole-body radioiodine scans were 97.6% and 100% and by stimulated thyroglobulin were 85.3% and 85.8% in group A and B, respectively (P = .62).


CONCLUSIONS
The use of low diagnostic (131)I activity (1.1 mCi) given 6 days prior to RAI was safe and convenient without adversely affecting the long-term clinical outcome.
Departments of Clinical Oncology (B.K.Y.) and Nuclear Medicine (B.M.), The Christie National Health Service Foundation Trust, Manchester M20 4BX, England, United Kingdom.
Beng Khiong
BK
Yap
Brian
B
Murby
D018265:Carcinoma, Papillary, Follicular / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000532:radiotherapy* / Q000601:surgery; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics / Q000627:therapeutic use*; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000453:epidemiology; D011184:Postoperative Period; D057234:Preoperative Period; D011379:Prognosis; D011829:Radiation Dosage; D011877:Radionuclide Imaging; D012189:Retrospective Studies; D013961:Thyroid Gland / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects / Q000601:surgery; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000532:radiotherapy* / Q000601:surgery; D013965:Thyroidectomy / Q000009:adverse effects / Q000379:methods; D016896:Treatment Outcome; D051598:Whole Body Imaging / Q000009:adverse effects* / Q000379:methods*
D007457:Iodine Radioisotopes