I-131 MIBG Therapy
Meta Iodo Benzyl Guanidine (MIBG) therapy is a novel method of treatment for patients with high risk advanced neuroblastoma including relapsed or refractory tumours. Neuroblastoma is a cancer of nerve tissue that mostly affects infants and young children.
This is a precise treatment that uses radiopharmaceuticals – radioactive iodine (I-131) to deliver radiation specifically to the tumour cells. MIBG therapy is a novel method that is more effective, less painful and less time-consuming (hospital stay) than other therapies.
How does it work?
MIBG is a complex that can be absorbed by some type of nerve tissue and neuroblastoma cells. This happens because MIBG is very similar to norepinephrine/noradrenaline, the neurotransmitter chemical, that is normally taken up by nerve cells.
The therapy combines MIBG with beta-emitting isotope I-131 to selectively target the tumour cells and deliver the killing radiation to these cells. I-131 MIBG aims to damage the cancer cells precisely and prevents harm to the surrounding healthy tissue.
Procedure
- The patient is admitted to the special Nuclear Medicine Therapy Room or Radioisotope Therapy Isolation Room.
- The I-131 MIBG is a clear fluid that is administered through an IV or a central venous catheter over a period of three to four hours.
- The patient will be simultaneously given fluids for hydration and other medications if required.
- The hospital of the three to five days is usually required for the therapy. Sometimes, the child may have to stay longer so that the radiation level comes down to the safe level.
- The radiation level is checked every day at the hospital by the Radiation Safety Officer (RSO)
The patient will need to take oral medication to prevent thyroid damage caused due to the radioactive iodine in the I-131 MIBG. The medicine will be given before the treatment begins and will be continued for three weeks.
Caution
While most of the radioactive drug concentrates in the tumour cells, it also travels to bodily fluids such as sweat, spit, and urine – and still remains radioactive. People around the patients such as the caregivers are vulnerable to radiation exposure and need to take certain precautions. The patients are admitted to the specialized high-dose radioisotope therapy isolation room which is designed with lead walls and floors to minimize radiation exposure. The caregivers are supposed to stay behind the portable lead sheets surrounding the patient’s bed. As the patient’s bodily waste such as urine is also radioactive, special lead pipes are used to discard it and stored in a special waste storage facility. The waste in kept here for three months, after which it can be disposed of as normal medical waste
The radiation safety officer and doctors work closely with the parents of the children receiving the therapy to provide the day-to-day care.
At home:
A small amount of radioactivity still remains in the body even after the levels come down to a safe mark. Therefore, after discharge from the hospital, the doctor provides safety instructions that should be followed at home.
The caregiver has to ensure that the post-discharge follow-up is implemented after the discharge. This includes:
- The child continues to take the Thyroid Protecting Agent for four weeks, as instructed by the doctor.
- Having a Complete Blood Count (CBC) at least twice a week after leaving the hospital.
- The patient will most likely require platelets and red blood cell transfusions for a few weeks post-therapy.
- If the Neutrophil count falls below 0.75, the patient may need GCSF (Granulocyte Colony Stimulating Factor), a type of growth factor to help the white blood cells recover from the treatment. Depending on count recovery, the child may require reinfusion of his/ her stem cells.
- A follow-up MIBG Scan to be done 9-12 weeks post-treatment.
Outlook
About 30-40% of children with refractory or relapsed neuroblastoma have shown improvements in I-131 MIBG therapy. This makes it one of the most active agents for relapsed disease. The therapy may not cure the disease but it allows the patients to have more control over their condition and makes it possible to have a prolonged disease stabilization.
Potential risks and complications
Common side effects include nausea, dry mouth, irritation in salivary glands and reduced number of blood cells (red and white) and platelets produced by the bone marrow. The patient may need transfusions for blood and platelet as well as stem cell infusions.
Some less likely side effects include a decrease in thyroid function. This leads to problems such as fatigue, weight gain, and constipation. Patients may also require lifetime treatment with a supplement for the thyroid gland. Other problems such as infertility, high or low blood pressure, thinning of hair, infection because of low white blood cells. Patients may also have bleeding or bruising due to low platelets along with loss of appetite.