Radioactive iodine (RAI) therapy is a method of killing tumors by using the iodine uptake properties of thyroid cells to allow radioactive iodine-131 (I-131) to be absorbed by thyroid cancer cells.
It has been more than 70 years since the first human use of RAI for differentiated thyroid cancer in 1946, and RAI has played an irreplaceable role in reducing recurrence rates and improving outcomes, and is now the routine adjuvant treatment for differentiated thyroid cancer after surgery.
RAI treatment has several main purposes:
- Clear nail, to remove residual postoperative thyroid tissue;
- Clear foci, to destroy metastases that cannot be removed by surgery;
- adjuvant therapy to detect and destroy microscopic residual cancer tissue that may exist after surgery and reduce the risk of recurrence.
In recent years, there has been some new understanding and exploration of the “old” RAI treatment. A brief overview is provided below.
Who needs RAI treatment?
Who needs RAI?
- Who needs RAI?
Genetic testing helps assess risk of relapse
Genetic testing helps assess risk of relapse
Currently, patients who need RAI treatment are: patients with differentiated thyroid cancer who have undergone total or near-total thyroidectomy and whose postoperative pathology suggests a high risk of recurrence. If metastatic lesions are present, RAI therapy is required even if they are low to intermediate risk.
The 2015 American Thyroid Association guidelines list several indicators for assessing “high risk of recurrence,” which can be found below:
In addition, the 2015 US guidelines detailed gene mutations for the first time, emphasizing the important role of genetic molecular markers in assessing the risk of recurrence, particularly BRAF mutations. Therefore, if genetic testing reveals the presence of a BRAF mutation, it can help your doctor assess your risk of recurrence.
ps-Tg is not a reliable indicator for assessing the risk of relapse
ps-Tg (known as I-131 pre-treatment stimulated Tg, preablation stimulated Tg) is the serum thyroid gland level measured at high thyroid stimulating hormone (TSH) levels in the absence of postoperative levothyroxine tablets. The level of serum thyroglobulin (Tg) measured at high levels of thyrotropin (TSH).
In the past, the medical community believed that high ps-Tg levels tended to indicate a high risk of recurrence and that lower ps-Tg meant a lower risk of recurrence and that RAI treatment could be avoided. However, the new concept in recent years is that high ps-Tg still indicates a high risk of recurrence, but low ps-Tg levels no longer indicate a low risk of recurrence, and the decision to do RAI therapy should not be based on ps-Tg alone, but should be evaluated in conjunction with neck ultrasound and whole-body radioiodine imaging.
Problems in RAI treatment and countermeasures
Countering the “stuttering effect” with new technology
The “stutter effect” simply means that after a diagnostic dose of I-131 is administered first, the lesion no longer takes up the therapeutic dose of I-131 and thus does not achieve the desired effect.
In response, it has been suggested that I-123 could be used instead of I-131, or a lower dose of I-131, in diagnostic radioiodine examinations.
Other recent research suggests that cancer cells could be reintroduced to iodine using genetic recombination. However, this new technology is still in the research phase and has not been applied in the clinic.
Rational selection of therapeutic dose
Research in recent years has confirmed that increasing the dose of I-131 in patients with a low or intermediate risk of recurrence does not significantly reduce recurrence rates and improve outcomes, but rather increases the side effects associated with radioiodine therapy. Therefore, reducing the dose of I-131 therapy has become the latest philosophy.
Coping with treatment-induced psychological problems
I-131 treatment may cause psychosomatic abnormalities such as depression. The causes are often multifaceted, such as treatment-induced hypothyroidism (“hypothyroidism”), isolation during treatment, and fear of cancer.
If you feel unresponsive, apathetic, indifferent to what is going on around you, or uninterested in anything, have difficulty concentrating, or have poor comprehension, you should seek early psychiatric care.
Family members also need to be aware of the patient’s mental state and provide more care and attention. Helping patients get out of their mental haze requires the joint efforts of family members and medical staff.
Co-written by Dr. Shuwen Yang, Cancer Hospital of Fudan University