Radiopharmaceuticals

نظرة عامة

Radiopharmaceuticals are medicines that contain a small amount of a radioactive substance. Healthcare professionals use them to diagnose and treat many diseases and conditions.

When used for diagnosis, radiopharmaceuticals are put into the body before an imaging test. The medicine builds up in the area of concern. A camera in the imaging machine detects the radiation. The test makes pictures that show the parts of the body that take up the medicine.

When used for treatment, radiopharmaceuticals with stronger radiation are put into the body. The medicine travels to the area that needs treatment and releases the radiation. The medicine gives radiation directly to the part of the body that needs it.

Using radiopharmaceuticals to diagnose and treat diseases is an area of healthcare called nuclear medicine.

Types of radiopharmaceuticals

Many radiopharmaceuticals exist. Each contains a radioactive substance called a radionuclide, which is an isotope that gives off radiation. Some radionuclides naturally seek out certain kinds of cells and can be used on their own. Other radionuclides need help getting to the right place. In those cases, the radionuclides are attached to a substance that targets certain cells. This substance carries the radiation to the target cells.

Radiopharmaceuticals can be used for diagnosis, treatment or both. The difference between those used for diagnosis and those used for therapy is the type and amount of radiation given off. In general, the radioactivity in therapeutic radiopharmaceuticals lasts longer and gives a higher dose of radiation in order to treat disease.

Diagnostic radiopharmaceuticals are used with imaging tests to help diagnose diseases and conditions. Radiopharmaceuticals used for diagnosis are called radioactive tracers. They also are called radiotracers. Imaging tests that use radiotracers are sometimes called nuclear medicine imaging tests or molecular imaging tests. Examples include single-photon emission computerized tomography (SPECT) scans and positron emission tomography (PET) scans.

Examples of nuclear medicine imaging tests include:

• Bone scan.
• Choline C-11 PET scan.
• Hepatobiliary iminodiacetic acid (HIDA) scan.
• Molecular breast imaging.
• Nuclear cardiology stress test.
• Parathyroid scan.
• Positron emission tomography (PET) scan.
• Prostate-specific membrane antigen (PSMA) PET scan.
• Single-photon emission computerized tomography (SPECT) scan.

Therapeutic radiopharmaceuticals are used to treat diseases and conditions. These treatments are sometimes called radiopharmaceutical therapy, nuclear medicine therapy, peptide receptor radionuclide therapy (PRRT), radioligand therapy and targeted radiotherapy.

Examples of radiopharmaceutical therapies include:

• Bone-seeking therapy with radium Ra-223 (Xofigo).
• PRRT with lutetium Lu-177 dotatate (Lutathera).
• PSMA therapy with lutetium Lu-177 vipivotide tetraxetan (Pluvicto).
• Radioactive iodine therapy with sodium iodide I-131 (Hicon).
• Radioimmunotherapy with yttrium Y-90 and ibritumomab tiuxetan (Zevalin).

Theranostic radiopharmaceuticals are medicines that help with both diagnosis and treatment. The diagnostic form of the medicine shows where the disease is in the body. It helps the healthcare team see if the treatment is likely to work. The therapeutic form targets those same areas to deliver treatment.

One example is PSMA therapy for prostate cancer. This treatment targets prostate cancer cells that make a protein called prostate-specific membrane antigen (PSMA). To see if treatment might work, the healthcare team does a PSMA PET scan with a diagnostic radiopharmaceutical that targets PSMA. If the cancer cells take up a lot of the medicine, it's a good sign that the treatment may work. The therapy uses a radiopharmaceutical that targets PSMA, but with a higher dose of radiation to treat the cancer.

لماذا يتم ذلك؟

Radiopharmaceuticals are used to diagnose and treat many different diseases and conditions.

Radiopharmaceuticals for diagnosis

Nuclear medicine imaging uses radiopharmaceuticals called radiotracers to diagnose diseases and conditions. This kind of imaging makes pictures that tell the healthcare team about how the body is functioning. It's different from X-rays and CT scans, which show what the area of concern looks like. Nuclear imaging gives clues about how well the cells and tissues are working.

A healthcare professional might recommend nuclear medicine imaging when other tests don't give enough information. Nuclear imaging might help avoid more-invasive procedures. It also might show signs of disease before they show up on an anatomic imaging test, such as an X-ray or CT scan.

Examples of conditions that can be diagnosed with nuclear medicine imaging include:

• Brain conditions. Tests such as brain PET and brain SPECT can help diagnose Alzheimer's disease, brain tumors, Parkinson's disease, cognitive decline, seizures, stroke, essential tremor and other brain conditions.
• Heart conditions. Tests such as cardiac PET and cardiac SPECT can help diagnose heart failure, coronary artery disease, cardiac amyloidosis, cardiac sarcoidosis and other heart conditions.
• Cancers. PET scans are used to diagnose many cancers, including prostate cancer, breast cancer, pancreatic cancer, skin cancer, bladder cancer, kidney cancer and others. PET scans also can help look for signs that the cancer has spread to the lymph nodes or other parts of the body. The scans also can assess whether treatment is working.
• Thyroid conditions. These include thyroid cancer, hyperthyroidism, thyroid nodules, thyroiditis and other conditions.
• Parathyroid conditions. Nuclear medicine tests, such as SPECT and PET, can help locate any parathyroid glands that are not typical. This may help with hyperparathyroidism treatment.
• Gallbladder and bile duct conditions. Nuclear medicine biliary scans can help diagnose cholecystitis, gallbladder cancer, complications of gallbladder surgery and other conditions.
• Bone conditions. Bone scans and other nuclear medicine imaging tests can help diagnose broken bones, bone infections, arthritis, bone cancer, bone metastasis and other bone conditions.
• Other conditions. These can include lung conditions, kidney conditions, lymphedema, infections, internal bleeding and cerebrospinal fluid leaks.

Radiopharmaceuticals for treatment

Radiopharmaceutical therapy delivers radiation directly to the target cells. The medicine travels through the body to the target site. Once there, the radioactive part of the medicine gives off alpha particles or beta particles. These energetic particles don't travel far, so the radiation mainly affects the target area. The radiation causes breaks in the DNA inside cells and causes them to die.

Conditions treated with radiopharmaceutical therapy include:

• Cancer that spreads to the bones. Radium Ra-223 (Xofigo) helps treat prostate cancer that spreads to the bones. It contains a radioisotope that targets areas of bone that have been hurt by cancer.
• Lymphoma. Yttrium Y-90 and ibritumomab tiuxetan (Zevalin) help treat lymphoma. This treatment uses a substance that targets a protein on lymphoma cells called CD20.
• Neuroendocrine tumors. Lutetium Lu-177 dotatate (Lutathera) treats advanced neuroendocrine tumors, including pancreatic neuroendocrine tumors and carcinoid tumors. It has a substance that targets cancer cells that have receptors for a chemical called somatostatin.
• Prostate cancer. Lutetium Lu-177 vipivotide tetraxetan (Pluvicto) helps treat metastatic prostate cancer when other treatments haven't helped. It has a substance that targets a protein called PSMA on prostate cancer cells.
• Thyroid conditions. Sodium iodide I-131 (Hicon) helps treat thyroid cancer and hyperthyroidism. This treatment is sometimes called radioactive iodine therapy. It uses a radioactive form of iodine that's naturally taken up by thyroid cells.

Radiopharmaceutical therapy is an active area of cancer research. Many other treatments are being studied.

المخاطر

Radiopharmaceuticals are safe medicines. As with all medicines, they have some risks and side effects. The side effects may depend on whether the radiopharmaceutical is used for diagnosis or treatment.

All radiopharmaceuticals contain a small amount of a radioactive substance, which exposes you to radiation. For imaging tests, radiotracers usually have a very low dose of radiation. It's usually not enough to cause any side effects. Radiopharmaceutical therapy typically uses higher doses in order to treat disease. This level of radiation can cause side effects such as feeling very tired, dry mouth, and nausea and vomiting.

Healthcare professionals use the lowest amount of radiation that's needed to get accurate results or effective treatment. They make sure the benefits outweigh the possible risks. High doses of radiation raise the risk of cancer, so healthcare professionals use a safe low dose. If you are concerned about radiation, talk about it with your healthcare team.

Radiotracer side effects

Side effects of radiopharmaceuticals used for diagnosis depend on the medicine you receive and how it's given.

In general, side effects may include:

• A metallic taste in the mouth.
• An area of blood called a hematoma that forms around the spot where the needle goes into the skin.
• Headache.
• Nausea and vomiting.
• Skin irritation around the place where the needle goes into the skin.

Radiopharmaceutical therapy side effects

Side effects of radiopharmaceuticals used for treatment may depend on the reason for the treatment and what medicine you receive. Ask your healthcare professional what you can expect.

In general, side effects may include:

• Allergic reaction to the medicine.
• Diarrhea.
• Dry mouth.
• Feeling very tired and weak.
• Infertility.
• Joint and muscle pain.
• Kidney damage.
• Liver damage.
• Low blood cell counts, which can raise the risk of infections and easy bruising.
• Nausea and vomiting.
• Short-term increase in cancer pain before it starts to get better.
• Slightly increased risk of cancer in the future.
• Throat pain, with treatments for thyroid conditions.

كيف تستعد؟

Follow any instructions your healthcare team may give you to help you prepare for receiving a radiopharmaceutical. Your care team might give you instructions about:

• Food and drink. Some tests and procedures might require you to stop eating and drinking for several hours before your appointment. Some might require you to follow a specific diet. Others might ask you to drink more fluids before your test or procedure.
• Medicines. For most tests, your care team might tell you to continue taking your medicines as usual. Some treatments might require changing how you take your medicines. Follow the instructions from your care team.
• Clothing. In general, wear comfortable clothing to your appointment. For an imaging test, you might need to change into a gown, so wear clothes that are easy to get on and off.

Before your test or treatment, tell your healthcare team:

• About any allergies or bad reactions you've had to any medicines, foods, iodine or latex.
• About any medicines you take, including medicines that you can buy without a prescription, as well as any vitamins or supplements that you take.
• If you are pregnant or breastfeeding.

ما يمكن أن تتوقعه

What you can expect during a procedure that involves radiopharmaceuticals depends on the reason for the procedure.

Radiopharmaceuticals for diagnosis

Radiopharmaceuticals for nuclear imaging are typically given through a vein in the arm. Some are injected into the skin or around the nerves. Others are swallowed or inhaled.

After receiving the radiotracer, you may wait before you have the imaging test. This gives the radiotracer time to move through your body. For some tests, the wait is short. For other tests, you might wait a few hours. A few radiotracers need a day or more, so you might leave and come back on another day for the imaging test.

When it's time for the imaging test, you may go to a room that has the imaging machine. The healthcare professionals who do the test might ask you to lie on a flat table. For some tests, such as PET scans, the table moves slowly through a machine that contains the scanner. For other tests, such as SPECT scans, the table stays still while the scanner moves around you.

Nuclear imaging scans don't cause pain. You may need to hold still during the scan and this can cause discomfort. If you feel a lot of discomfort, tell the healthcare professionals who are monitoring you.

After the scan, you rest while your healthcare team checks the scans. The care team reviews the scans to ensure no more are needed. Once they decide you are done, you can leave and go about your day.

Nuclear imaging can take an hour or more. The amount of time depends on the test you're having. The scan part of the test often doesn't take long. The other parts of the test, such as waiting for the radiotracer to move around the body, add to the length of the appointment.

After nuclear imaging, the radiation usually leaves the body quickly through urine and stool. Drinking water helps flush the radiotracer from your body. For most radiotracers, the radiation goes away within a few days.

Radiopharmaceuticals for treatment

Most people receiving radiopharmaceutical therapy don't need to stay in the hospital. However, some treatments may require a hospital stay. Ask your healthcare team what you can expect during your treatment.

Most treatments are given through a vein. You might feel a pinch as a healthcare professional puts a needle into your skin. This usually doesn't hurt. You typically won't feel anything as the medicine goes into your body. Radioactive iodine therapy for hyperthyroidism and thyroid cancer comes as a liquid or capsule that you swallow.

Some radiopharmaceutical treatments are given once. Others are repeated several weeks apart for a set number of sessions.

An appointment for radiopharmaceutical therapy usually takes a few hours. Sometimes it takes all day. Ask your healthcare team what you can expect. Bring something to help you pass the time.

You can go home after your treatment. Your care team may ask that you not go to work or to social activities for a few days.

After treatment, the radiation leaves through body fluids, such as urine, stool, sweat and tears. Most of this happens soon after treatment. Your healthcare team gives you instructions to follow to help you limit radiation exposure to others for the first few days after treatment. Instructions may include:

• Avoid close contact with children and people who are pregnant.
• Do not have sexual contact. When it's safe to resume sexual activity, you may need to use birth control for several months after treatment.
• Sleep alone.
• Use a separate toilet from others in your home, if possible, and flush the toilet twice each time you use it.

Once most of the radiation leaves your body, it's safe to go back to your life as usual. A low level of radiation stays in the body for a few months. This low level isn't harmful to others. But it can be found with detectors such as those at airports, train stations, border crossings and other high-security places. Your healthcare team may give you a letter or card to carry with you that explains your treatment.

النتائج

Ask your healthcare team when you can expect to know the results of your radiopharmaceutical test or treatment. Nuclear imaging results might be available soon after your test. It often takes time to know the results of radiopharmaceutical therapy.

Nuclear imaging test results

Nuclear imaging test results are given in a radiology report. The doctor who looks at the images writes the report. This doctor may be a nuclear medicine doctor or a radiologist. The report is for the healthcare professional who ordered the test, so it often has medical terms that can be hard to understand.

A radiology report typically includes:

• The type of test and how it was performed, including the radiopharmaceutical used and the type of imaging machine.
• The reason for the test, including important parts of your medical history and results of other tests you've had.
• What the test results show, including places in the body with radiotracer uptake. Uptake means a place where the radiotracer built up in the cells. Uptake in an area that's not expected might be a sign of disease. Some uptake in healthy tissues is expected. This is called physiologic radiotracer uptake, and it usually isn't a sign of disease.
• What the results mean, which might be described as the impression, and the next tests that are recommended.

Radiopharmaceutical therapy results

Results of radiopharmaceutical therapy treatments may take time. Ask your healthcare professional what you can expect. You might have imaging tests to check how well the treatment is working.