Post-surgical thyroid ablation with low or high radioiodine activities results in similar outcomes in intermediate risk differentiated thyroid cancer patients

Abstract

Background: In differentiated thyroid cancer (DTC) patients at intermediate risk of recurrences, no evidences are provided regarding the optimal radioactive iodine (RAI) activity to be administered for post-surgical thyroid ablation. Methods: This study aimed to evaluate the impact of RAI activities on the outcome of 225 DTC patients classified as intermediate risk, treated with low (1110-1850 MBq) or high RAI activities (R3700 MBq). Results: Six to 18 months after ablation, remission was observed in 60.0% of patients treated with low and in 60.0% of those treated with high RAI activities, biochemical disease was found in 18.8% of patients treated with low and in 14.3% of patients treated with high RAI activities, metastatic disease was found in 21.2% of patients treated with low and in 25.7% of patients treated with high RAI activities (PZ0.56). At the last follow-up (low activities, median 4.2 years; high activities, median 6.9 years), remission was observed in 76.5% of patients treated with low and in 72.1% of patients treated with high RAI activities, persistent disease was observed in 18.8% of patients treated with low and in 23.5% of patients treated with high RAI activities, recurrent disease was 2.4% in patients treated with low and 2.1% in patients treated with high RAI activities, deaths occurred in 2.4% of patients treated with low and in 2.1% of patients treated with high RAI activities (PZ0.87). Conclusion: Our study provides the first evidence that in DTC patients at intermediate risk, high RAI activities at ablation have no major advantage over low activities.

Radioiodine treatment after surgery for differentiated thyroid cancer: a reasonable option

“…To rule out occult nodal metastatic disease with 90% confidence, six LNs would need to be submitted for pathologic examination for patients with T1b tumors, nine LNs for patients with T2 tumors, and 18 LNs for patients with T3 disease [27]. Most concerning is that lymphadenectomy is often limited or not performed in 50-70% cases, especially when the patients are a priori considered to belong to the lowor intermediate-risk groups [25].…”

“…While low 131 I activities (1.1 GBq; 30 mCi) successfully ablate normal thyroid tissue remnant located in the thyroidectomy bed [19,20], effective treatment for iodine-avid regional and distant metastatic disease has traditionally required higher 131 I activities, as demonstrated by lesion dosimetry calculation studies [21][22][23][24]. It is important to discuss the study of Castagna et al [25], which assessed the effectiveness of 1. [26].…”

Prescribed Activity of 131I Therapy in Differentiated Thyroid Cancer

“…Castagna et al (1) evaluated the effectiveness of 1.11-1.85 GBq (30-50 mCi) versus at least 3.7 GBq (100 mCi) of 131 I for the treatment of 225 patients who had DTC and were classified as being at intermediate-risk. In that study, the authors evaluated patients for remission, recurrent disease, biochemical disease, persistent disease, and death.…”

Festina Lente and the “Crab and the butterfly”

“…Specifically, in the treatment of differentiated thyroid cancer (DTC), "less" is frequently promoted as "better" with (1) less frequent surgeries, (2) if surgery is to be performed, then less extensive surgeries (e.g., lobectomy versus near total thyroidectomy), (3) less frequent I-131 therapies, and (4) if an I-131 therapy is to be performed, then lower prescribed activities of I-131 administered [1] .…”

“…In the selection of I-131 prescribed activity (dosage) for the treatment of patients with suspected but unproven residual DTC to reduce the patients' recurrence rates (adjuvant treatment as defined by the American Thyroid Association [1] ), Castagna et al [2] published a valuable study evaluating the effectiveness of 30 mCi vs. 100 mCi of I-131 for the treatment of such patients. In brief, the authors evaluated rates of recurrent disease, biochemical disease, metastasis, persistent disease, or death.…”