Comparable Ablation Efficiency of 30 and 100 mCi of I-131 for Low to Intermediate Risk Thyroid Cancers Using Triple Negative Criteria.

BACKGROUND: There is controversy about ablation efficacy of low or high doses of radioiodine-131 (RAI) in patients with differentiated thyroid cancers (DTC). The purpose of this prospective study was to determine efficacy of 30 mCi and 100 mCi of RAI to achieve successful ablation in patients with low to intermediate risk DTC. MATERIALS AND METHODS: This prospective cross sectional study was conducted from April 2013 to November 2015. Inclusion criteria were patients of either gender, 18 years or older, having low to intermediate risk papillary and follicular thyroid cancers with T1-3, N0/N1/Nx but no evidence of distant metastasis.Thirty-nine patients were administered 30 mCi of RAI while 61 patients were given 100 mCi. Informed consent was acquired from all patients and counseling was done by nuclear physicians regarding benefits and possible side effects of RAI. After an average of 6 months (range 6-16 months; 2-3 weeks after thyroxin withdrawal), these patients were followed up for stimulated TSH, thyroglobulin (sTg) and thyroglobulin antibodies, ultrasound neck (U/S) and a diagnostic whole body iodine scan (WBIS) for ablation outcome. Successful ablation was concluded with stimulated Tg< 2ng/ml with negative antibodies, negative U/S and a negative diagnostic WBIS (triple negative criteria). ROC curve analysis was used to find diagnostic strength of baseline sTg to predict successful ablation. RESULTS: Successful ablation based upon triple negative criteria was 56% in the low dose and 57% in the high dose group (non-significant difference). Based on a single criterion (follow-up sTg<2 ng/ml), values were 82% and 77% (again non-significant). The ROC curve revealed that a baseline sTg level ≤ 7.4 ng/ml had the highest diagnostic strength to predict successful ablation in all patients. CONCLUSIONS: We conclude that 30 mCi of RAI has similar ablation success to 100 mCi dose in patients with low to intermediate risk DTC. A baseline sTg ≤ 7.4 ng/ml is a strong predictor of successful ablation in all patients. Low dose RAI is safer, more cost effective and more convenient for patients and healthcare providers.

Baseline stimulated thyroglobulin level as a good predictor of successful ablation after adjuvant radioiodine treatment for differentiated thyroid cancers.

BACKGROUND: To determine the predictive value of the baseline stimulated thyroglobulin (STg) level for ablation outcome in patients undergoing adjuvant remnant radioiodine ablation (RRA) for differentiated thyroid carcinoma (DTC). MATERIALS AND METHODS: This retrospective study accrued 64 patients (23 male and 41 female; mean age of 40±14 years) who had total thyroidectomy followed by RRA for DTC from January 2012 till April 2014. Patients with positive anti-Tg antibodies and distant metastasis on post-ablative whole body iodine scans (TWBIS) were excluded. Baseline STg was used to predict successful ablation (follow-up STg<2 ng/ml, negative diagnostic WBIS and negative ultrasound neck) at 7-12 months follow-up. RESULTS: Overall, successful ablation was noted in 37 (58%) patients while ablation failed in 27 (42%). Using the ROC curve, a cut-off level of baseline STg level of ≤14.5 ng/ml was found to be most sensitive and specific for predicting successful ablation. Successful ablation was thus noted in 25/28 (89%) of patients with baseline STg≤14.5 ng/ml and 12/36 (33%) patients with baseline STg>14.5 ng/ml ((p value<0.05). Age>40 years, female gender, PTS>2 cm, papillary histopathology, positive cervical nodes and positive TWBIS were significant predictors of ablation failure. CONCLUSIONS: We conclude that in patients with total thyroidectomy followed by I-131 ablation for DTC, the baseline STg level is a good predictor of successful ablation based on a stringent triple negative criteria (i.e. follow-up STg <2 ng/ ml, a negative DWBIS and a negative US neck).

Controversies about radioactive iodine-131 remnant ablation in low risk thyroid cancers: are we near a consensus?

Well differentiated thyroid cancers (WDTC), including papillary (80%) and follicular (10%) types, are the most common endocrine cancers globally. Over the last few decades most the diagnosed cases have fallen into low risk categories. Radioactive iodine-131 (RAI) has an established role in reducing recurrence and improving the survival in high risk patients. In patients with primary tumor size <1 cm, RAI is not recommended by many thyroid societies. However, low risk WDTC has been an arena of major controversies, most importantly the role and dose of adjuvant RAI for remnant ablation to minimize chances of recurrence and improving survival. This review is an attempt to update readers about the previous and existing practice based on results of non- randomized trials and evolving trends fueled by recently published randomized studies.