TriangleHEALTH PROFESSIONAL · SOURCE READING
Radioactive iodine (RAI) therapy
Source: Thyroid Cancer Treatment (PDQ®)–Health Professional Version, National Cancer Institute.
Source updated: May 9, 2025 · Captured 2026-09-09.
Selected source text with whitespace normalised. This Triangle page is not an NCI PDQ summary.
Studies have shown that a postoperative course of therapeutic (ablative) doses of radioiodine 131I results in a decreased recurrence rate among high-risk patients with papillary and follicular carcinomas.[5] RAI may be given in addition to exogenous thyroid hormone but is not considered routine.[12] RAI treatment is optimal after total thyroidectomy with minimal thyroid remnant. With a large thyroid remnant, a low thyroglobulin level cannot be achieved, which increases the chance of requiring multiple doses of RAI.
Consideration of RAI for remnant ablation is based on the following pathological risk features:
The size of the primary tumor.
The presence of lymphovascular invasion.
Capsule invasion.
The number of involved lymph nodes.
RAI may be given with one of two methods of thyroid-stimulating hormone (TSH/thyrotropin) stimulation:
Withdrawal of thyroid hormone.
Administration of recombinant human thyrotropin (rhTSH).
Administered rhTSH maintains quality of life and reduces the radiation dose delivered to the body compared with thyroid hormone withdrawal.[13] Patients presenting with papillary thyroid microcarcinomas (tumors <10 mm), which are considered to be very low risk, have an excellent prognosis when treated surgically. Additional therapy with 131I would not be expected to improve the prognosis.[14]
The role of RAI in low-risk patients is not clear because disease-free survival (DFS) or overall survival (OS) benefits have not been demonstrated.
Evidence (surgery with or without RAI):
One study reviewed 1,298 patients with low-risk disease from the French Thyroid Cancer Registry.[15] Patients were identified as having low-risk papillary or follicular cancer as defined by the following American Thyroid Association and European Thyroid Association criteria:
Source links and citations
One study reviewed 1,298 patients with low-risk disease from the French Thyroid Cancer Registry.[15] Patients were identified as having low-risk papillary or follicular cancer as defined by the following American Thyroid Association and European Thyroid Association criteria:
Complete tumor resection.
One study reviewed 1,298 patients with low-risk disease from the French Thyroid Cancer Registry.[15] Patients were identified as having low-risk papillary or follicular cancer as defined by the following American Thyroid Association and European Thyroid Association criteria:
Multifocal tumors 1 cm or smaller confined to the thyroid.
One study reviewed 1,298 patients with low-risk disease from the French Thyroid Cancer Registry.[15] Patients were identified as having low-risk papillary or follicular cancer as defined by the following American Thyroid Association and European Thyroid Association criteria:
Tumors larger than 1 cm but no larger than 4 cm confined to the thyroid.
One study reviewed 1,298 patients with low-risk disease from the French Thyroid Cancer Registry.[15] Patients were identified as having low-risk papillary or follicular cancer as defined by the following American Thyroid Association and European Thyroid Association criteria:
No lymph node involvement or distant metastatic disease.
Of the 1,298 patients, 911 patients received RAI after surgery, and 387 patients did not receive RAI after surgery. The follow-up period was 10.3 years.
In multivariate analyses, there were no differences in OS (P = .243) or DFS (P = .2659), according to RAI use.[15]
Source links and citations
Long-term complications of RAI with 131I include:
Second malignancies.
Sialadenitis.
Lacrimal and salivary gland dysfunction.
Options for decreasing radiation exposure in patients with low-risk thyroid cancer have been explored. These options have included reducing the amount of RAI in each dose and giving RAI in combination with rhTSH injections.
Evidence (thyroid hormone withdrawal or use of rhTSH with 131I):
A phase III, randomized, noninferiority study included patients with low-risk thyroid cancer. The study compared two thyrotropin-stimulation methods (thyroid hormone withdrawal or use of rhTSH) and two 131I doses (1.1 GBq [30 mCi] and 3.7 GBq [100 mCi]), using a 2 × 2 factorial design.[16][Level of evidence C1]
Source links and citations
A phase III, randomized, noninferiority study included patients with low-risk thyroid cancer. The study compared two thyrotropin-stimulation methods (thyroid hormone withdrawal or use of rhTSH) and two 131I doses (1.1 GBq [30 mCi] and 3.7 GBq [100 mCi]), using a 2 × 2 factorial design.[16][Level of evidence C1]
Thyroid ablation rates were equivalent between high- and low-dose 131I at 6 to 10 months after administration of 131I.
A phase III, randomized, noninferiority study included patients with low-risk thyroid cancer. The study compared two thyrotropin-stimulation methods (thyroid hormone withdrawal or use of rhTSH) and two 131I doses (1.1 GBq [30 mCi] and 3.7 GBq [100 mCi]), using a 2 × 2 factorial design.[16][Level of evidence C1]
Patients with more advanced T stage (T1–T3, N0–1) and with less than a total thyroidectomy were included with a lower overall ablation rate of 85%.
Another phase III, randomized, noninferiority study of patients with low-risk thyroid cancer compared two thyrotropin-stimulation methods (thyroid hormone withdrawal or use of rhTSH) and two 131I doses (1.1 GBq [30 mCi] and 3.7 GBq [100 mCi]), using a 2 × 2 factorial design. The inclusion criteria consisted of a low-risk, homogeneous cohort. All of the patients underwent total thyroidectomy and had pathological TNM stage pT1 (≤1 cm) and N1 or NX, pT1 (>1–2 cm) and any N, or pT2, N0 without thyroid capsule extension/distant metastases.[17][Level of evidence C1]
Source links and citations
Another phase III, randomized, noninferiority study of patients with low-risk thyroid cancer compared two thyrotropin-stimulation methods (thyroid hormone withdrawal or use of rhTSH) and two 131I doses (1.1 GBq [30 mCi] and 3.7 GBq [100 mCi]), using a 2 × 2 factorial design. The inclusion criteria consisted of a low-risk, homogeneous cohort. All of the patients underwent total thyroidectomy and had pathological TNM stage pT1 (≤1 cm) and N1 or NX, pT1 (>1–2 cm) and any N, or pT2, N0 without thyroid capsule extension/distant metastases.[17][Level of evidence C1]
Thyroid ablation rates were equivalent between high- and low-dose 131I at 6 to 10 months after administration of 131I.
Another phase III, randomized, noninferiority study of patients with low-risk thyroid cancer compared two thyrotropin-stimulation methods (thyroid hormone withdrawal or use of rhTSH) and two 131I doses (1.1 GBq [30 mCi] and 3.7 GBq [100 mCi]), using a 2 × 2 factorial design. The inclusion criteria consisted of a low-risk, homogeneous cohort. All of the patients underwent total thyroidectomy and had pathological TNM stage pT1 (≤1 cm) and N1 or NX, pT1 (>1–2 cm) and any N, or pT2, N0 without thyroid capsule extension/distant metastases.[17][Level of evidence C1]
Complete thyroid ablation rate was 92%.
Another phase III, randomized, noninferiority study of patients with low-risk thyroid cancer compared two thyrotropin-stimulation methods (thyroid hormone withdrawal or use of rhTSH) and two 131I doses (1.1 GBq [30 mCi] and 3.7 GBq [100 mCi]), using a 2 × 2 factorial design. The inclusion criteria consisted of a low-risk, homogeneous cohort. All of the patients underwent total thyroidectomy and had pathological TNM stage pT1 (≤1 cm) and N1 or NX, pT1 (>1–2 cm) and any N, or pT2, N0 without thyroid capsule extension/distant metastases.[17][Level of evidence C1]
Patients who underwent thyroid hormone withdrawal had more symptoms of hypothyroidism associated with deterioration in quality of life than the patients who received rhTSH.
Neither study assessed the effect of low-dose RAI on long-term recurrences or survival. The studies also did not address whether RAI could be safely omitted in specific low-risk groups.
Publication references
Read the original reference and check its publication notices.
Preserved source evidence · Not medical advice