Radioactive iodine (I-131) therapy for thyroid cancer

Thyroid cancer is one of the most common endocrine tumors, and thanks to advances in diagnostics and therapy, the prognosis for most patients today is exceptionally good. One of the specific and highly effective methods of treating thyroid cancer is radioactive iodine therapy, also known as ablative or adjuvant iodine-131 (I-131) therapy.

What is radioactive iodine therapy?

The thyroid gland is the only organ in the body that naturally absorbs iodine. When the radioactive isotope iodine (I-131) is used, it selectively accumulates in thyroid cells, including any remaining tumor cells after surgery.

This method allows for the targeted destruction of thyroid cells that were not removed by surgery – whether they are located in the neck, lymph nodes, or distant metastases, without much effect on the rest of the body.

When is it used?

Radioiodine therapy is most often used after total thyroidectomy (removal of the thyroid gland), especially in the following cases:

• Differentiated thyroid carcinomas (papillary and follicular)

• Presence of an increased risk of recurrence or spread of the disease

• Microscopic tumor remnants

• Metastatic disease (in the lymph nodes, lungs, bones, etc.)

In low-risk tumors (smaller, without affected lymph nodes), iodine therapy is sometimes not necessary.

What does the procedure look like - what to expect?

Before therapy, it is necessary to increase the level of TSH (thyrotropin) in order to stimulate the absorption of iodine into the thyroid cells. This is achieved by:

• Temporarily stopping replacement therapy with levothyroxine, or

• Using recombinant TSH (Thyrogen)

  
  

Arrival for radioactive iodine therapy is usually arranged and organized in advance. When the patient arrives at the hospital, the first thing to do is to be admitted - the medical staff will once again check the findings, the dose of therapy and the conditions for administration. In most cases, the patient is placed in a special isolated room within the nuclear medicine department, which is equipped to protect the environment from radiation. The radioactive iodine itself is administered in this room – usually in the form of a capsule that the patient swallows with water. The procedure takes only a few seconds and is painless.

After that, the patient remains in the room alone, to prevent unnecessary exposure of other people to radiation. Depending on the dose and the institution's protocol, the patient stays in the hospital for one to three days, and medical staff contact the patient via intercom or come briefly and protected, wearing lead aprons. Food is brought to the door of the room, and the patient is recommended to drink plenty of fluids to eliminate radiation from the body as quickly as possible. For many patients, the greatest challenge is isolation, but with good preparation – books, a tablet, films or music – most report that their stay went without major difficulties. The exact number of days of isolation depends on the dose and the recommendations of the doctor and medical physicist.

After administration - isolation and precautions

After discharge, the patient receives clear written instructions on how to behave at home (isolation, hygiene, avoiding close contact), as well as appointments for further control.

Radioactive iodine is excreted through urine, sweat and saliva, so for a few days after administration it is necessary to:

• Avoid close contact with pregnant women and young children

• Sleep separately

• Drink plenty of fluids and urinate frequently

• Practice thorough hygiene

Side effects and risks

The therapy is generally well tolerated, but possible side effects include:

• Temporary dry mouth (due to the effect on the salivary glands)

• Taste changes

• Mild nausea

• In rare cases - changes in blood or damage to other organs (with high cumulative doses)

Pregnant and breastfeeding women should not receive radioactive iodine therapy.

Post-therapy monitoring

In the months following therapy, the following is monitored:

• Thyroglobulin level – a tumor marker for differentiated cancers

• Whole body scintigraphy – performed after the first dose to assess the spread of the disease

• Follow-up ultrasound examinations and blood tests

Patients who have received radioactive iodine also remain on thyroid hormone replacement therapy for life.

Conclusion

Radioactive iodine therapy is a proven effective and targeted method of treating thyroid cancer. When used correctly, it has a high success rate and significantly reduces the risk of recurrence. The decision on therapy is made individually, based on the characteristics of the tumor, surgical findings and laboratory indicators, in consultation with the oncologist and/or nuclear medicine specialist. For any additional questions and doubts, talk to your doctor – an informed and active role of the patient is an important step in any oncological treatment.