Nuclear medical examinations play an important part in differentiated thyroid cancer, both for therapy follow-up and for localization of local recurrence. Radioactive iodine is important for postoperative ablation, treatment of small metastases, and diffuse lung metastases. Postoperative radioactive iodine (131I ) therapy is given to patients with a high risk of recurrence after surgery.
Examinations with radioactive iodine play a small role in the primary work-up of thyroid cancer. The diagnostic total-body scan with 200-700 MBq 131I is no longer performed before therapy, because the diagnostic dose may inhibit the subsequent uptake of the therapeutic dose (stunning), and also because a diagnostic scan has much less sensitivity for detection of remaining tissue compared to a post therapy scan. A diagnostic scan with123I can be utilized without the danger of stunning, but the medication is costly.
A diagnostic scan with131I /123 I in addition to a post-therapy scan can be taken advantageously as a SPECT/CT.
Differentiated thyroid cancer after a thyroidectomy in the presence of one of the following factors:
- solitary papillary thyroid carcinoma 1-2 cm in largest diameter
- multifocal papillary thyroid carcinoma
- papillary cancer with metastases to regional lymph nodes
- papillary cancer with extra thyroidal growth and vessel infiltration and with Tall cell variant
- invasive follicular cancer with or without regional or distant metastasis
- minimally invasive follicular cancer > 4 cm
- minimally invasive follicular cancer with regional or distant metastases. Generally more liberal for patients between 20-45 years and with Hûrthle cell variation.
- iodine-concentrating metastases
- diffuse lung metastases
- Inspect whether there is surrounding iodine contentrating tissue concentrated in the neck, or if there is iodine-concentrating in metastases.
Postoperative radioactive iodine therapy
- Ablation of remaining thyroid tissue to better monitor the level of s-tyroglobulin.
- Minimize the frequency of recurrence by ablation of microscopic remains of cancer tissue.
- Treatment for metastases.
Treatment for metastasis
- Ablation of metastases (iodine-concentrating)