What Is Radiopharmaceutical Therapy?
Radiopharmaceuticals belong to a class of medications that are considered systemic radiation therapies. These medications contain radioactive substances that help alleviate bone pain when cancer metastasizes (or spreads) to the bones. The most common radiopharmaceuticals used in the treatment of prostate cancer-related bone pain include Strontium-89 (MetastronTM), Samarium-153 (Quadramet®), and Radium-223 (Xofigo®). These drugs are typically given as intravenous (IV) injections. Radiopharmaceuticals are typically indicated for individuals with prostate cancer that has metastasized to the bones and has accompanying pain. Radium-223 may be used for patients with castrate-resistant prostate cancer (prostate cancer that is not responding to treatment to lower the body’s level of testosterone) that has spread (metastasized) only to the bones and is causing symptoms, and has not spread to other areas of the body. Radium-223 may be a part of a patient's prostate cancer treatment to help them live longer, as opposed to only helping to relieve pain. It may be necessary to remain in the hospital for one to two days post-treatment with a radiopharmaceutical.
Radiopharmaceuticals may be used in addition to other treatment options, including external beam radiation. Individuals taking radiopharmaceuticals should be monitored for decreases in blood cell counts, however, these counts should return to normal after treatment. Individuals taking radiopharmaceuticals should also be counseled on the proper safety guidelines to follow for themselves and others they are in immediate contact with.1-3
What are the ingredients in radiopharmaceuticals?
The active ingredient in radiopharmaceuticals is the radioactive element present in each medication that will decay and target cancer cells.
How do radiopharmaceuticals work?
The radioactive elements in radiopharmaceuticals are attracted to areas in the body that are experiencing rapid bone turnover. Our bodies are continuously building and destroying our bones in a balanced process that keeps us healthy and strong. Cells in our body called osteoclasts regularly break down bone to release minerals, like calcium into our blood stream. Our body also builds bone using cells called osteoblasts, and takes these nutrients, like calcium, out of the blood and puts them back into our bones when needed. This process is critical to our skeletal stability and maintaining our nutrient balance. When cancer metastasizes to the bones, it begins to constantly break down bones, overwhelming the destruction process, while the healthy cells in the body try to build it back up. This process creates rapid cell turnover that the radiopharmaceuticals are drawn to.
Radiopharmaceuticals selectively deposit in metastatic bone lesions, releasing local radiation, decreasing bone pain. The exact mechanism by which this whole process occurs is still largely under investigation, however, pain relief is typically a result of treatment with radiopharmaceuticals, and individual’s often feel relief within 1-4 weeks.
It has been reported that pain relief from radiopharmaceuticals can last up to 18 months, and can decrease the need for other pain medications, including addictive opioids. Additionally, individuals treated with radiopharmaceuticals may potentially be treated more than once if necessary, however, this may depend on how patients respond to treatment.1,2
What are the possible side effects of radiopharmaceuticals?
Multiple clinical trials evaluated the safety and efficacy of different radiopharmaceuticals. Although side effects may vary with the specific radiopharmaceutical used, the side effects may include vomiting, diarrhea, nausea, and swelling of the limbs. This is not an exhaustive list of all potential side effects of radiopharmaceuticals. Talk to your healthcare provider or pharmacist for further information.4
Things to note about radiopharmaceuticals
Since radiopharmaceuticals utilize radioactive elements, it is important that individuals taking these medications are given proper safety instructions to follow to minimize any unnecessary radiation-related risks of treatment. This includes reducing both an individual’s risk, as well as decreasing the risk of harmful radiation effects to those around them including your loved ones or caregivers. You should avoid intimate and sexual contact for several days after receiving this form of therapy. Some of these guidelines may include:
- Remaining in the hospital for 1-2 days post-treatment
- Staying well hydrated and monitoring fluid intake and urine output
- Follow good hygiene practices to prevent radiation exposure through bodily fluids
- Always use the toilet for urination and defecation, and flush the toilet twice after use
- Wash linens soiled with urine, fecal matter, or other bodily fluids separately from other linens in the household
- Handle anything with bodily fluids with gloves and appropriate safety gear
- Use condoms when sexually active or avoid sexual activity all together
Since treatment with radiopharmaceuticals can decrease blood cell counts, individuals taking these medications should be monitored and have their blood cell counts tested regularly. Additionally, since blood cell counts may be low, individuals taking radiopharmaceuticals should report any signs of infection, like fever, or bleeding to their provider immediately.
Before starting radiopharmaceuticals talk to your provider if you:
- Have low red or white blood cell or platelet counts or a condition that affects the amount of these cells in your body
- Are sexually active with a partner who is pregnant or who could become pregnant
- Are allergic to the medication or any of its ingredients
- Have any other medical conditions
- Are currently taking any other medications (prescription and over-the-counter), vitamins, or herbal supplements
You should also contact your provider if you notice any signs of an allergic reaction to the medication, including chest pain, fever, flu-like symptoms, or difficulty breathing. It is also important to consult the prescribing information for any other medications prescribed with your radiopharmaceutical.4
Radiopharmaceuticals can be prescribed in varying dosages depending on the medication being used. Radiopharmaceuticals are typically administered via an intravenous (IV) injection. It may be necessary to receive the injection in a special radiation-safe room or to remain in the hospital 1-2 days post-treatment. Your provider will determine what the optimal dosage and administration schedule is for your radiopharmaceutical, as well as for any other medications taken in addition to it. Patients should talk to their doctor if they have any questions, or if they have questions regarding their radiopharmaceutical regimen.4
These are not all the possible side effects of radiopharmaceuticals. Patients should talk to their doctor about what to expect with treatment.