Overview of Radioactive Iodine Therapy for Thyroid Malignancies
Thyroid cancer is the most common cancer affecting the endocrine system (a group of glands that produce hormones to regulate your body’s functions). There are five main types of thyroid cancer: papillary thyroid, follicular thyroid, oncocytic cell cancer, medullary thyroid, and anaplastic thyroid cancer. Among these different types, the most common ones are papillary thyroid, follicular thyroid, and oncocytic cell cancers. In fact, papillary thyroid cancer alone makes up 80-90% of all cases of thyroid cancer, and it also has the best outlook for recovery.
The usual treatment for these types of thyroid cancers involves surgery, and in some cases, it may be followed by a treatment known as radioactive iodine therapy. Unlike other types of radiation therapy, radioactive iodine specifically targets cells in the thyroid gland because of the way thyroid cells absorb iodine. This is useful because it means the radioactive iodine can destroy cancer cells while having little effect on other parts of the body.
When a person receives radioactive iodine therapy, they’re given a form of iodine called sodium iodide I 131, which releases radiation. Because the thyroid gland absorbs iodine so efficiently, the radioactive iodine goes straight to the thyroid cells. Once inside the cells, the radiation severely damages the cancerous cells, causing them to die. In addition, a small amount of the radioactive iodine can also get into the bloodstream and reach any other cancer cells that may have spread to other parts of the body from the thyroid. This ability to target both local and distant cancer cells makes radioactive iodine therapy a powerful tool in treating thyroid cancer.
Looking at how common thyroid cancer is globally, it comes in at seventh place, but it does have a very high five-year survival rate, at 98.4%. There are different forms of thyroid cancer, with papillary, follicular, and oncocytic types being those that originate from a specific group of cells in the thyroid. There are also more aggressive types of thyroid cancer, such as poorly differentiated and anaplastic cancers. Another type is medullary thyroid cancer which comes from a different type of cell in the thyroid. Women are almost four times more likely to get early-stage thyroid cancer than men, although the rate of undetected thyroid cancer is the same in both men and women.
After a person has had surgery to remove thyroid cancer, they may be given an initial dose of radioactive iodine to destroy any remaining thyroid tissue and cancer cells. If any cancer cells recur or remain, further radioactive iodine treatments may be given. Doctors use techniques such as blood tests, ultrasound imaging of the neck, and iodine scanning to assess the presence and status of disease after surgery and guide the choice of further therapy.
Anatomy and Physiology of Radioactive Iodine Therapy for Thyroid Malignancies
The thyroid gland, which is a part of our body’s endocrine system, develops an important part of its development pathway while we are still in the womb. Starting near the back of tongue, it gradually moves down to its final location in the front of the neck by the time we are seven weeks old in our mother’s womb. This gland, shaped like a butterfly, has two lobes linked by an isthmus, a small band of tissue. Some people have a common variation called a pyramidal lobe that extends from this isthmus. The thyroid gland is securely attached to the windpipe.
Now, to understand how the thyroid gland functions, we should know that it is highly dependent on iodine, which we get from our diet. This iodine is absorbed from the food we eat and distributes all over our body when it gets into our bloodstream. In the thyroid gland, the iodine is concentrated in special cells called thyroid follicular cells. These cells start working on iodine around the 12th week of a baby forming in the womb. When a hormone called Thyroid Stimulating Hormone (TSH) acts upon iodine, it gets fused with an amino acid tyrosine to form thyroid hormones. These hormones, once released into our body, help regulate our body’s metabolism. Other than being used to produce these hormones, the iodine also leaves our body through urine, and also in small amounts via faeces, sweat and saliva.
Turning the focus to thyroid cancer, each type comes about from a different cause or path. Generally, these cancer cells budding from thyroid follicular epithelium have mutations or changes in their DNA sequence that provoke them to become aggressive. Most papillary thyroid cancers develop as a result of disruptions in protein pathways, while follicular thyroid cancers usually have mutations in certain genes. As these cancers advance from being well-differentiated to poorly-differentiated, they acquire even more mutations that further changes their behaviour.
Radiation therapy often works well for differentiated thyroid cancers that still have the ability to absorb iodine. This is because iodine, especially radioactive iodine, can be used to destroy these cancer cells. However, for types of thyroid cancer that are poorly differentiated, radiation therapy is not as effective because they lose the ability to absorb iodine. During radioactive iodine therapy, I-131 iodine is used to kill cancer cells by giving out beta particles. But this therapy also induces gamma-emission that brings about public radiation concerns due to the release of high-energy photons.
For radioactive therapy to be successful, it’s crucial that the radiation is delivered at a set rate to prevent tumor cells from repairing the damage caused by the initial lower doses of radiation. So, the success of therapy hinges on each dose rather than the additive effect of several smaller doses.
Why do People Need Radioactive Iodine Therapy for Thyroid Malignancies
If you have a differentiated thyroid cancer, which includes papillary and follicular thyroid carcinomas that respond well to treatment, your doctor may recommend a treatment called radioactive iodine after completing surgery to remove your thyroid. To decide the right dose and whether you will benefit from this treatment, your doctor will assess your health condition after surgery. They do this by taking a blood test to measure a protein called thyroglobulin, doing an ultrasound scan of your neck, and taking an image of your body using radioactive iodine.
The radioactive iodine treatment is aimed at achieving three main things:
- Killing any remaining benign (non-cancerous) thyroid tissue after total or partial thyroid surgery. This makes it easier when imaging the body with radioactive iodine and assessing thyroglobulin levels in future. It also helps tell if there’s any disease recurrence or spread of the disease to other parts of the body, which is called metastatic disease.
- Serving as an additional treatment after surgery to minimize the chances your cancer will come back, especially if you have a moderate or high risk of recurrence. This treatment increases the chances you will remain disease free for a longer time, even if you have tiny pockets of disease that are not measurable or visible (subclinical micrometastases).
- Killing any remaining cancer or treating recurring disease with the goal to cure or alleviate symptoms if cure is not feasible. This has a positive effect on disease-free survival and overall survival.
Radioactive iodine therapy is recommended if your tumor is larger than 2 cm and at least one risk factor is present, such as extension of the cancer beyond the thyroid, being 45 years or older, or having spread to lymph nodes or distant parts of the body. If your tumor is smaller than 2 cm, radioactive iodine therapy is suggested if there is evidence of distant spread of cancer.
To know whether you will benefit from radioactive iodine therapy, your doctor will consider several factors and classify you into a low-risk, intermediate-risk, or high-risk category:
- Low risk: Individuals with a certain type of thyroid cancer called papillary carcinoma, who have had the entire visible tumor surgically removed and don’t show spread to lymph nodes or distance organs, invasion into local structures or blood vessels, or an aggressive tissue pattern under the microscope. These individuals also don’t have radioactive iodine uptake outside the area where the thyroid was removed or swelling of the lymph nodes and microscopic spread to lymph nodes. Certain subtypes of papillary and follicular thyroid cancers confined to the thyroid and showing invasion into the capsule that surrounds the thyroid also fall into this category.
- Intermediate risk: Patients usually have aggressive types of thyroid cancers and may also include patients with multiple small papillary cancers showing extension beyond the thyroid and patients with swelling of the lymph nodes or more than five microscopic lymph node spread.
- High risk: If you were not able to have all your tumor removed, if the tumor noticeably extended beyond the thyroid, if your lymph nodes were affected with at least one being greater than 3 cm, or if you had spread of the cancer to distant places in your body. This also applies if you have more than four foci of vascular invasion in follicular carcinoma.
The right dose of radioactive iodine is decided with a team approach. If after your initial definitive surgery there is no evidence of disease by imaging, biochemical testing, pathological testing, or clinical symptoms, then you should either be observed or undergo radioactive iodine treatment, depending on the protocol at your treating health institution.
Radioactive iodine therapy is mainly used to treat differentiated thyroid cancers, as they are able to take up iodine. This therapy is often recommended under the following situations:
– If your cancer has significantly spread beyond your thyroid to other parts of your body.
– If your cancer has spread into your blood vessels.
– If your thyroglobulin levels remain high 6 to 12 weeks after surgery, as this might mean there are residual thyroid cancer cells.
– If your tumor was associated with a large number or more than five cancerous lymph nodes, as this suggests you have a high risk of your cancer returning.
– If your tumor is a differentiated or hybrid carcinoma, because these types of cancers are typically more responsive to radioactive iodine therapy due to their ability to absorb iodine.
The aim of radioactive iodine therapy is to get rid of any leftover thyroid tissue or cancer cells after having surgery, particularly in patients who have a higher chance of their cancer coming back or spreading to other parts of the body.
When a Person Should Avoid Radioactive Iodine Therapy for Thyroid Malignancies
If a woman is pregnant or breastfeeding, she should not receive radioactive iodine therapy. This treatment could harm a baby’s thyroid because the radioactive substance can pass through the placenta to the unborn child or through breast milk to a nursing infant. So, it’s important to verify a woman is not pregnant before giving this therapy. If a woman is nursing, she should stop breastfeeding before starting this treatment.
Other health issues like vomiting and diarrhea can also make radioactive iodine treatment unsafe. This treatment relies on the body’s ability to absorb the radioactive iodine, something that can be affected by these conditions. Additionally, these symptoms could increase the risk of spreading radioactivity to other people.
People who do not follow safety instructions, such as those related to radiation protection, should not receive this treatment. The same applies for those who have recently taken certain medications, undergone imaging tests involving iodine, or have problems with controlling urine or bowel movements. All these conditions must be discussed before starting treatment.
Before starting therapy, healthcare professionals should explain the need for radiation protection to patients. This includes what actions need to be taken to protect others from radiation exposure. Completing a thorough check-up and understanding the patient’s history in relation to the disease can lead to better results and reduce the risk of radiation exposure to others.
According to a study, there’s no significant difference in the risk of heart disease between individuals with thyroid cancer who received radioactive iodine treatment and those who did not. This information should be considered when deciding whether this treatment is appropriate for patients who already have heart disease.
Equipment used for Radioactive Iodine Therapy for Thyroid Malignancies
Radioactive iodine treatment is a common process used to treat thyroid cancer. It’s essential that this is done safely and effectively, which means doctors need a range of specialized equipment and materials:
– 131I: You might be expected to swallow a pill or liquid that contains 131I, a radioactive substance. The special thing about 131I is that it’s attracted to thyroid cancer cells. Once inside your body, it goes straight to these cells and starts causing damage which helps treat your cancer. The fact that 131I specifically targets thyroid tissue is what makes it effective in treating differentiated thyroid cancer.
– Radiation Safety Materials: Given that 131I is radioactive, a certain level of safety is required to use it. With the goal of protecting both the medical team and the patient, doctors use lead-lined rooms and radiation shielding materials, for example, lead aprons. They may also use mobile shielding units that help with containing radiation.
– Dosimetry Equipment: Tools like Geiger-Muller counters, ionization chambers, and scintillation detectors ensure the correct amount of radiation is given to a patient, while keeping exposure of the medical team to a minimum. Real-time dosimetry monitoring ups the precision and safety of the process.
– Lead-lined containers: To safely store and transport radioactive iodine capsules or liquid solutions, they are carried in lead-lined containers that protect against radiation exposure.
– Radiation Survey Instruments: Handheld devices like Geiger-Muller counters are used to keep an eye on radiation levels in the treatment room and surrounding areas, ensuring that exposure stays within safe limits.
– Isolation Facilities: Some patients who receive high doses of radioactive iodine have to stay in a room alone to prevent exposing others to radiation. These rooms are designed with special shielding and ventilation, and come with a way to dispose of waste safely. Remote monitoring technologies like cameras help to keep contact with patients to a minimum, making the process safer.
– Radiation Safety Accessories: Healthcare staff also use tools like lead aprons, gloves, goggles, and protective clothing to guard themselves against contamination and exposure during the treatment process.
– Medical Imaging Equipment: Devices like gamma cameras might be used before and after the radioactive iodine treatment to check on how the treatment is working and see where the radioactive iodine has spread in your body.
– Thyroid Uptake Systems: Special probes are used to see how well your thyroid is absorbing the radioactive iodine, which helps doctors decide on the dosage for your treatment and checks how effective the treatment has been.
– Radiation Detection Badges: To monitor exposure during treatments, healthcare staff wear badges that detect radiation. These are checked regularly to make sure the levels stay within safety limits.
All in all, the tools and materials required to treat thyroid cancer using radioactive iodine include radioactive materials, containment and shielding for the radiation, dose monitoring, patient isolation facilities, safety tools, and medical imaging equipment. These resources are vital for making sure the treatment is done safely and effectively, while keeping risks to patients and healthcare staff to a minimum.
Who is needed to perform Radioactive Iodine Therapy for Thyroid Malignancies?
If you have thyroid cancer, your doctor might use radioactive iodine to treat it. This treatment involves a team of medical professionals, each with specific roles:
First, a surgeon performs a procedure called a thyroidectomy, where they remove your thyroid gland before the radioactive iodine is administered. Once your thyroid is gone, an endocrinologist, a doctor specialized in hormones, takes over the treatment plan. They’ll check how your thyroid is functioning, manage any medication you need before or after the treatment, and adjust it if necessary.
A medical oncologist, a cancer specialist, also helps plan and coordinate your overall cancer treatment. They’ll evaluate whether radioactive iodine therapy is the right choice for you and keep an eye on your progress, looking for any signs that the cancer has come back or if you’re having any unpleasant reactions to the treatment.
Then there are the nuclear medicine professionals. They oversee your radioactive iodine treatment, assessing whether you’re a good candidate for the therapy, calculating how much iodine you need, and supervising the treatment plan and its administration.
It’s common for radiation oncologists, doctors who specialize in cancer treatments that use radiation, to be involved too. They’re especially necessary if the cancer has spread beyond your thyroid. They’ll work with the other medical professionals to ensure an integrated approach to your care.
The radioactive materials used for the therapy, such as I-131, are prepared and given to you by nuclear medicine technologists. These healthcare professionals ensure that all safety protocols are followed during your treatment and will explain to you what is happening, offering support along the way.
Radiation safety officers are responsible for overseeing radiation safety practices in the medical facility. They’re there to make sure everything is up to standard and in line with regulatory requirements. They provide training for staff and monitor radiation exposure levels to minimize risks for you and the healthcare personnel.
Medical physicists, specialists in radiation therapy, may be included in your team. They ensure you receive the exact radiation dose prescribed, while also minimizing exposure to the surrounding tissues. They’re involved in treatment planning, dose calculation, and quality assurance.
Nurses play a crucial role in your care during radioactive iodine treatment. They will check on you before treatment, monitor you during, and provide care to manage any side effects or complications. They’ll teach you about any radiation safety precautions you need to take and tell you how to take care of yourself after the treatment.
Also, radiology technicians might be involved. They perform imaging tests (like body scans) before and after your treatment. These tests allow the team to see how your treatment is working and to check for any remaining or spread disease.
The administrative staff coordinate logistics, schedule appointments, and provide support during the treatment. They’ll be in charge of any paperwork you need and help keep everything running smoothly.
Other healthcare providers, like physician assistants, psychologists, social workers, and rehabilitation specialists, may also be part of the team taking care of you when you’re undergoing radioactive iodine treatment. Each team member’s role is vital in ensuring the safe and effective delivery of radioactive iodine. By working together, this team is able to provide you the best care and treatment outcomes.
Preparing for Radioactive Iodine Therapy for Thyroid Malignancies
Before starting radioactive iodine therapy, a treatment option often used for certain types of thyroid diseases like cancer, there is some important prep work. The two crucial steps are:
1. Boosting the levels of TSH (thyroid-stimulating hormone), a critical hormone that assists the radioactive iodine in targeting thyroid cells.
2. Reducing the intake of regular iodine from your diet so that the radioactive iodine isn’t diluted or lessened by the presence of regular iodine.
One way of boosting TSH is by stopping thyroid hormone treatments, which, although may result in a temporary condition called hypothyroidism, is beneficial for this preparation process. Also, it’s suggested to follow a diet low on iodine for 1-2 weeks. Considering iodine can influence the effectiveness of radioactive iodine, limiting its consumption allows the radioactive iodine to work better.
If stopping your thyroid hormone medication could create undesirable effects, there’s an alternative: using a medication called recombinant human TSH (rhTSH), which can artificially increase your TSH levels.
Before starting the treatment, doctors will generally carry out some tests. They’ll examine your kidney function as the radioactive iodine is primarily taken out of your body through urine, and any existing kidney issues may result in the slower removal of the iodine, hence raising the risk of bone marrow suppression. You’ll also be required to fast (not eat anything) for 2-4 hours before, and an hour after, the treatment.
The risks, benefits, and possible side effects of the treatment will be explained to you, and you’ll be asked to give consent to undergo the procedure. If there’s a need for more treatments or hormone replacement therapy later on, this will also be discussed.
Female patients within childbearing age will need to take a pregnancy test before starting the treatment, and breastfeeding moms will be advised to stop breastfeeding at least six weeks before treatment. During the therapy period, drinking lots of water is encouraged to help flush out the radioactive iodine more effectively.
Your physicians will also prepare you for the treatment in the following ways:
1. They’ll advise you about the specific dietary restrictions you need to follow to make the treatment more effective, such as reducing intake of food high in iodine.
2. They will confirm the status of pregnancy and breastfeeding, if applicable, to ensure safety for you and the baby.
3. They’ll conduct imaging studies and blood tests to map out the extent of your thyroid cancer and overall health.
4. You may need to self-isolate after the treatment to prevent others from getting exposed to radioactivity. You’ll be given clear guidelines on how to manage your isolation period.
5. You’ll be asked to drink plenty of fluids before, during and after the treatment.
6. They will educate you about what to expect during and after the treatment, possible side effects, precautionary measures, and post-treatment care. They’ll also guide you on managing some common symptoms like dry mouth, nausea, and fatigue.
Prepping for this treatment is crucial to make the most out of it – the better prepared you are, the safer and more successful your therapy can be.
How is Radioactive Iodine Therapy for Thyroid Malignancies performed
Standard treatment for thyroid cancer involves a surgery to remove the cancerous tissues and a process called radioactive iodine ablation. However, this doesn’t work in about 10% of differentiated thyroid cancers and all anaplastic thyroid cancers. For such advanced cases, doctors sometimes add in chemotherapy, but this doesn’t always prove to be very successful.
Radioactive iodine ablation is used after surgery to treat any remaining cancer, especially when there’s a chance the disease can return or spread elsewhere in the body. It’s shown to lower the chances of the cancer coming back and helps patients live longer.
This treatment is usually scheduled about 3 weeks after surgery. You may need to stop taking levothyroxine – a common thyroid medication – for about 4 to 6 weeks before this treatment, to make sure the levels of your thyroid-stimulating hormone (TSH) are high enough. If needed, a medicine called rhTSH can be used. It’s given as an injection for two days, and then the radioactive iodine treatment is given 24 hours later. The radioactive iodine is typically given as a pill.
Before you take this pill, the medical team need to make sure they’re giving it to the right person. Depending on your risk of the cancer returning, the dose of radioactive iodine will vary. If you’re at a low risk, a dose of about 30 mCi is generally enough. For those at a higher risk, the dose might be increased up to 250 mCi.
The medical team will explain all these processes to you and get your consent. The dose given to you is also cross-checked by an authorized professional. After you’ve taken the radioactive iodine, the medical team will check you and the surrounding area for any radioactivity before you can go home.
Before going home, you should drive alone if possible. If not, sit where you’re as far from others in the car as possible. For 3 to 4 days after the treatment, it’s advised that you limit close interactions with other people, use different bathrooms, avoid sharing drinks or food, and avoid close contact with children and pets. This is to minimize others’ exposure to any residual radiation.
The radioactive iodine has a half-life of 8.04 days, meaning that after this time, half of it will have decayed. This actually helps doctors because after a few days, they can scan your body again and see where the radioactive iodine has gone. If you have any cancer left, the radioactive iodine will concentrate in these areas, making them easier to see.
Radiation can be detected for several weeks after treatment, so if you’re planning on traveling, it’s important to keep documents about your treatment and hospital contact details. Also, anywhere between 4 to 6 months after the radioactive iodine treatment, doctors check how successful it was; if the cancer remains, the treatment might be repeated.
As part of the long-term treatment, you’ll probably need to take hormone replacement therapy and have regular check-ups with an endocrinologist, a doctor specializing in managing hormones and related disorders.
Possible Complications of Radioactive Iodine Therapy for Thyroid Malignancies
Using a sodium iodide I-131 treatment for conditions like thyroid cancer or Graves’ disease usually doesn’t severely harm patients. However, sometimes people experience side effects, both short and long term. This type of treatment involves the chemical I-131 concentrating in certain areas of your body like the thyroid, salivary glands, and stomach. Because of this, it can cause local tissue damage, leading to side effects that can last days to weeks (acute) or even longer (chronic).
In the short term, up to 20% of patients may experience inflammation of the salivary glands, known as sialadenitis, leading to dry mouth or xerostomia. Other acute side effects could include a change in your sense of taste, upset stomach or inflammation in your gut after the chemical passes through your system, pain and inflammation in your thyroid (radiation thyroiditis), and potentially blockage of the tear ducts in your eyes.
About a third of the people who receive this treatment experience a decrease in their saliva production, with about 10% of those having severe dry mouth. Some patients, especially those with a high dose of radiation, may see a temporary decrease in their blood platelet and white blood cells, which usually returns to normal levels in about two months.
In terms of long term side effects, men may see a reduction in their fertility, and other chronic effects could include scarring in the lungs, chronic dry mouth or inflammation of the salivary glands, or excessive tearing due to chronic damage of the tear glands. The likelihood that this treatment may lead to leukemia or cancer in the salivary glands is debated among experts.
Besides, the treatment for thyroid cancer in children and young adults may increase the risk of blood cancers and other types of cancers, like those affecting the uterus, salivary glands, and stomach, and particularly breast cancer in women, many years down the line. Hence, it’s crucial that patients who undergo this treatment are monitored regularly for a long time.
What Else Should I Know About Radioactive Iodine Therapy for Thyroid Malignancies?
Radioactive iodine plays a dual role in managing thyroid cancer. Depending on the cancer’s characteristics, it can be used for both diagnosing and treating the disease. Around 90% of thyroid cancers can absorb this substance.
The most common type of thyroid cancer, called papillary thyroid carcinoma, is twice as likely to occur in women than in men. It frequently spreads to the lymph nodes in the neck. On the other hand, follicular carcinoma, another type of thyroid cancer, generally spreads through the bloodstream, often reaching the lungs and bones, and less commonly the liver and brain. If treated appropriately, most thyroid cancers have a good outlook. However, a type of thyroid cancer called Hurthle cell cancer often spreads and may not absorb radioactive iodine.
After complete removal of the thyroid gland through a surgery known as total thyroidectomy, the main treatment for thyroid cancer, patients may receive radioactive iodine six to eight weeks later. This decision depends on the specifics of the cancer. About two months after the surgery, patients might also get a full-body scan using a low dose of radioactive iodine. This scan checks for leftover thyroid tissue or cancer spread to lymph nodes or other parts of the body. The doctor’s team will decide the right amount of radioactive iodine for treatment based on the scan.
Patients may need follow-up scans and additional radioactive iodine treatments depending on their individual situations. A full-body scan taken 3 to 10 days after radioactive iodine treatment can be more effective at detecting disease than a low-dose scan as it involves a higher radiation dose. Blood tests for a substance called thyroglobulin are also recommended for monitoring patients who have had thyroid cancer treatment. Regular repeated treatments every 6 months to a year are essential to ensure the cancer is fully dealt with. However, it’s important to remember that radioactive iodine treatment has potential side effects and the treatment dose may need adjusting. Because titanium iodine emits high-energy radiation and lasts a long time in the body, it’s crucial to take precautions to protect against radiation exposure.
Studies have shown that radioactive iodine therapy can lower the risk of recurrence in children with differentiated thyroid cancer. Urinary iodine levels might also predict how the disease will progress in patients treated with radioactive iodine for differentiated thyroid cancer. High levels of iodine in the urine may be associated with a worse outlook. The spread of cancer to distant parts of the body is a strong predictor of disease progression.
