Thyroid Cancer Treatment (PDQ®): Treatment - Health Professional Information [NCI] - Stage I and II Papillary and Follicular Thyroid Cancer
I131: Studies have shown that a postoperative course of therapeutic (ablative) doses of I131 results in a decreased recurrence rate among high-risk patients with papillary and follicular carcinomas. For optimal treatment with RAI, total thyroidectomy is recommended with minimal thyroid remnant remaining. 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 pathological risk features including:
- Evaluation of 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 thyrotropin stimulation: withdrawal of thyroid hormone or recombinant human thyrotropin (rhTSH). Administered rhTSH maintains quality of life and reduces the radiation dose delivered to the body compared with thyroid hormone withdrawal. Patients presenting with papillary thyroid microcarcinomas (tumors <10 mm), which are considered to be very low risk, have an excellent prognosis when treated surgically, and additional therapy with I131 would not be expected to improve the prognosis.
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. One study reviewed 1,298 patients from the French Thyroid Cancer Registry. Patients were identified as having low-risk papillary or follicular cancer as they are defined by the American Thyroid Association and the European Thyroid Association criteria:
- Complete tumor resection.
- Multifocal pT1 <1 cm.
- pT1 >1 cm.
- pT2, pN0, pM0 (American Joint Committee on Cancer/Union Internationale Contre le Cancer [AJCC/UICC]) corresponds to stage I for patients younger than 45 years old.
- pT2, pN0, pM0 (AJCC/UICC) corresponds to stages 1 and 2 for patients older than 45 years old.
- pT1 and pT2 without lymph node dissection (Nx).
Of the 1,298 patients, 911 patients received RAI after surgery, and 387 patients did not receive RAI after surgery. 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.