Strontium Chloride Sr 89 (brand name Metastron) is a radioactive isotope given as an injection to patients in the treatment of bone cancer. It is similar in chemical formula to calcium and is absorbed by the human body in a like fashion, which gives it the unique ability to target bone tissue. It helps ease the pain of metastasized tumors that have spread to the bones from other parts of the body. The most common origin of these tumors is as a secondary cancer to prostate cancer in men and breast cancers in women.
Metastron is delivered to the patient in the form of a slow injection taking one to two minutes. It travels to and targets impacted bone tissue, where it helps relieve the pain of the patient, but can also shrink the tumors by preventing new abnormal cells from forming.
Radiopharmaceuticals first became available in the treatment of cancer in the 1940s in the form of phosphorus, but phosphorus affected more than the cancerous tissue with grave side effects and collateral damage to organs and tissue that were not cancerous.
Strontium Chloride Sr 89 was initially developed in the late 1980s and was approved for use in the early 1990s. 70% to 80% of patients given this treatment report a decrease in pain levels. The effectiveness of the treatment and the onset of pain relief usually takes seven to 21 days. Because Metastron functions as a calcium analog in the body, it interacts negatively with multivitamins containing extra calcium compounds. Patients for whom Metastron is indicated as treatment should stop taking multivitamins and supplements at least two weeks before the injection to prevent that interaction and maximize the effectiveness of the treatment. It is generally very well tolerated and represents an effective and efficacious medication in the treatment of bone cancer.
Metastron is not recommended for pregnant women and has not been tested for pediatric patients.
Strontium Chloride Sr 89 (Metastron) actually has very few serious side effects, which is one of the major reasons it is so effective in treatment protocols. In clinical trials and in post-marketing experience, the following side effects have been reported, but occur infrequently and are considered low risk:
Given its mechanism in the body, particularly in bone marrow, the most common side effect of Strontium Chloride Sr 89 (Metastron) is the depression of white blood cell counts and platelets. This makes the patient more susceptible to infection and a compromised immune system.
Metastron's effects on fertility in the long term has not been studied, but it is likely that it would have some effect on fertility.
Strontium Chloride Sr 89 is delivered by injection with the recommended dosage of 40 mCi/kg (1.5 MBq/kg). This dosing level is generally thought to be the optimal balance of palliative treatment and radioactivity for the patient. Dosing should be at intervals of at least 90 days to limit side effects, hematologic toxicity and radioactivity levels.
Strontium Chloride Sr 89 generally has a very low rate of interaction with other medications. There are medications that have adverse interactions, most are moderate and would not necessarily be contraindicated or prevent the use of Strontium Chloride. These include:
The most important interaction patients should avoid when they are in a Strontium Chloride Sr 89 protocol is with multivitamins with minerals. These supplements can alter the efficacy of Strontium Chloride. Patients should discontinue use of multivitamins at least two weeks before beginning use of Strontium Chloride.
Because Strontium Chloride Sr 89 (Metastron) works primarily in the patient's bone marrow, those patients who suffer from conditions that already impact their levels of bone marrow should not use Strontium Chloride unless absolutely necessary.
For any patient using Metastron, careful and regular monitoring of platelet and white blood cell levels is indicated, as well as tracking toxicity levels in bone marrow. The recommended protocol for checking those levels is every two weeks.
Given the depressed levels of platelets and white blood cells that patients will produce while under treatment with Strontium Chloride, they should make every effort to avoid people with infections and illnesses as their immune system will be compromised. Good nutrition and adequate levels of sleep and rest can help patients avoid the potential illnesses and general fatigue that can accompany treatment.
Women who are pregnant or could become pregnant should not be given injections of Strontium Chloride Sr 89. It can affect the fetus and there has been very little clinical study of the effects of Metastron on fetuses and infants.
It is also contraindicated for nursing mothers.
Strontium Chloride has not been studied in pediatric patients and should not be administered.
Because the medication itself is radioactive, it should only be administered by medical providers with specific training in the handling and injecting of radiopharmaceuticals.
Should another round of Strontium Chloride Sr 89 be indicated in a patient's treatment, the response to the initial dose should be studied carefully. Monitoring of bone marrow, platelets and white blood cell counts are critical as the dose of radioactivity delivered by Strontium Chloride is high.
For patients with a very limited life expectancy, the use of Metastron is contraindicated.
Metastron should only be used in the treatment of certain types of bone cancers. It is not indicated for the treatment of other forms of cancer.
To avoid radioactive contamination of other people in the first week after treatment, patients should avoid urinals and only use normal toilets. Any blood or other bodily fluids should be carefully wiped up and handled with great care.
Because of depressed platelet counts, patients should avoid accidental injury and any sort of activity that might lead to bruising.
Studies in animals have indicated that Strontium Chloride Sr 89 is a possible carcinogen when administered in high doses over time.
Strontium Chloride Sr 89 is a radioactive substance and so should be handled and stored with great care. Because it is delivered as an injection by a health care professional, it would not, as a rule, be stored in the home, but rather in a medical facility. It comes in 10mL vials that contain 148MBq, 4mCi. These vials are transported in containers with walls that are lined with a minimum of 3 millimeters of lead and two warning labels indicating the radioactivity of the contents.
The medication should always be stored in its original, lead lined container at temperatures between 15 and 25 degrees Celsius (59-77 degrees Fahrenheit).
Again, because of the radioactivity of the medication, the expiration date on the label should be strictly observed.
During the actual injection, medical care providers should observe all safety protocols to insure limited exposure to radioactivity of both the patient and the provider.
Strontium Chloride Sr 89 has been available for more than three decades as a treatment for bone cancers that have developed as a secondary cancer metastasized from prostate or breast cancers. The radioactive isotope is delivered by injection near the site of the bone cancer (where the tumors or lesions are). The isotope is metabolized in the body similarly to calcium and targets those cancerous cells. The radioactivity of the treatment serves to both reduce the pain caused by the lesions and to slow the growth of those cells.
This medication must be handled carefully and is transported to medical facilities in lead lined containers. It can only be administered to patients by physicians trained in the delivery of radioactive pharmaceuticals.
In clinical trials and then later in post marketing studies, Strontium Chloride has shown to have a 70%-80% rate of effectiveness in relieving pain for patients. Metastron takes one to three weeks from the date of injection to reach maximum effectiveness. It does have some side effects, but they tend to be mild and well tolerated by patients. The biggest dangers of this medication are its impacts on the immune system of the patient during treatment as it depresses white blood cell counts and platelets. This increases the risk of infection and injury to the patient. There are some possible long term effects of the use of this medication in terms of possible cancer risk and dangers it may pose to fertility.
Strontium Chloride also has very few serious drug interactions which makes it very useful in cancer treatment. It does interact negatively with other mineral supplements, such as multivitamins and calcium supplements, so patients should stop taking these medications at least two weeks prior to an injection of Metastron.
Strontium Chloride Sr 89 is only used in the treatment of bone cancer.