Specific therapies involving radiation
Frequently asked questions by the health professionals about:
» Antibody therapy
» Iodine-131 used in benign thyroid disease
» Iodine-131 used in thyroid cancer
» Iodine-131 lipidiol therapy
» Iodine-131 MIBG therapy
» Phosphorous-32 therapy for myeloproliferative disease
» Rhenium-188 therapy for palliation of bone pain
» Samarium-153 for palliation of bone pain
» Strontium-89 therapy for palliation of bone pain
» Yttrium-90 microspheres
» Radiation synovectomy with yttrium-90 silicate
Cancer therapy using labeled monoclonal antibodies is becoming more common. The radiation protection issues are similar to those for other forms of therapy using the same radionuclides.
Radionuclide and form
Iodine-131 labeled monoclonal antibodies, activity typically 3 GBq. Other radionuclides such as Y-90 may also be used.
Methodology
Intravenous injection. Thyroid blocking with potassium iodide mandatory prior to therapy with I-131, as there may be some free or dissociated I-131 in the bloodstream.
Excretion
Unbound or dissociated activity predominantly excreted via urine. Approximately 7% in the first week in the case of I-131 label.
External radiation
Similar to that for iodine-131 iodide therapy.
Post-discharge issues
Toilet precautions must be maintained for one week after administration.
Advice to patients and families
Similar to that for iodine-131 iodide therapy.
Emergencies
Similar to those for iodine-131 iodide therapy.
» Iodine-131 used in benign thyroid disease (thyrotoxicosis, Grave’s disease, toxic goitre)
Radionuclide and form
Iodine-131, as sodium or potassium iodide, in either liquid form, or in a gelatine capsule. Typical activity is up to ~1 GBq.
Methodology
Iodine is extracted from the gut into the bloodstream and taken up by functioning thyroid tissue. The thyroidal uptake may be as high as ~70%. The remainder is excreted.
Excretion
Radioiodine will be excreted from the patient primarily by the kidneys, and consequently, the patient should be encouraged to drink freely to minimize dose to kidneys, bladder and gonads. Benign disease patients normally have an intact thyroid, with high uptake, and they will have the slowest clearance. The next most significant pathway is saliva. This will manifest in contamination of eating and drinking utensils, and pillow coverings (due to saliva excretion during sleep). Lesser pathways are sweat and faeces (particularly when a capsule is used).
Breast milk can contain significant amounts of radioiodine, and patients who are breast-feeding must cease feeding before their therapy.
The proportion of each form of contamination (apart from urine) will vary widely, so it is best to assume that all are present, until proved otherwise. The excretion phase may not be complete before discharge, or will not have begun if the patient leaves immediately after administration of the radiopharmaceutical.
Post-discharge issues
Unless there is active excretion at time of discharge, the radiation safety problem is confined to external radiation. As the radioiodine, which remains, is mainly localized in thyroid tissue, there can be significant levels of radiation at short distances. If there is still excretion taking place, contamination of household objects, other persons, and the toilet may occur.
Advice to patients and families
Contamination
Even if excretion is still occurring at discharge, it is normally quite low in activity. Urinary excretion is normally promoted in hospital by frequent fluid intake, and this should be continued after discharge for a few days. Patients should be advised to flush the toilet twice after use, and males should avoid 'splashing' (sitting down to urinate is recommended). Patients should wash their hands frequently. Sharing food or eating utensils should be avoided. Daily showering will remove sweat. Clothing should be separately laundered. Breast feeding must cease before radioiodine therapy, and not be resumed under any circumstances.
If the patient is discharged immediately after administration, of the radiopharmaceutical, these precautions must be followed for at least a few days. Importantly, vomiting within 4-6 hours after oral administration of radioiodine in any form (i.e. before extraction from the gut is complete) will be a significant source of contamination. A patient who vomits should do so into a container or directly into the toilet, which must be flushed clean. The nuclear medicine department where the patient was treated must be notified, as the effectiveness of the therapy will be diminished.
To minimize cross contamination by exchange of fluids, kissing or sexual intercourse should be avoided for at least two days. A condom should be used for the first week after therapy. The condom will reduce the risk of contamination, but will not shield from the I-131 gamma radiation.
External radiation
In most cases, this is the most important safety issue. Once excretion is effectively complete, the external radiation will decline only with the effective half-life, which for iodine-131 is about 8 days. Family members, especially the spouse, and the public may potentially all receive significant exposures unless some basic precautions are followed, all for about 5-7 days unless otherwise specified:
At home, avoid prolonged close physical contact. A simple rule is to maintain at least an arm’s length distance, and preferably one metre, for short periods only. For extended periods, two metres.
Avoid all contact with children or pregnant women. If the patient has young children, who will demand physical contact, this should be allowed for short periods only. Ideally, the patient’s children should be accommodated elsewhere for a week.
Return to work should be postponed for at least two days, possibly longer.
There are cases where the contamination and external radiation measures can be modified, for example where the patient is elderly, and the other home occupant(s) are as well. Then the radiation risk is low, and only measures which are easy to take are necessary. The nuclear medicine staff where the therapy is performed will be able to give more specific advice.
Emergencies
In a case of patient illness or accident requiring attendance by a doctor or at a hospital, the medical staff involved must be notified of the therapy, and the date, radionuclide and activity involved. As mentioned above, the nuclear medicine department must be notified of vomiting within 4-6 hours of the therapy.
» Iodine-131 used in thyroid cancer
Radionuclide and form
Iodine-131, as sodium or potassium iodide, in either liquid form, or in a gelatine capsule. Typical activity is up to ~6GBq
Methodology
Iodine is extracted from the gut into the bloodstream and taken up by functioning thyroid tissue (including active metastases). In malignant disease, where the patient has had a total or subtotal thyroidectomy prior to therapy, the uptake may be as low as 2%. The remainder is excreted.
Excretion
Radioiodine will be excreted from the patient primarily by the kidneys, and consequently, the patient should be encouraged to drink freely to minimize dose to kidneys, bladder and gonads.
Thyroid cancer patients undergoing their initial treatment may still have an appreciable amount of thyroid tissue, and will have a much lower clearance rate. Patients undergoing a second or later treatment will have less thyroid tissue, and thus have a higher clearance rate.
In cancer patients, because of the lack of thyroid tissue, most of the administered activity will appear in the urine. The fraction will largely be determined by the amount of remnant and metastatic thyroid tissue. In most cases, 50-60% of the administered activity is excreted in the first 24 hours, and around 85% over a stay of 4-5 days. This represents a significant potential for radioactive contamination.
The next most significant pathway is saliva. This will manifest in contamination of eating and drinking utensils, and pillow coverings (due to saliva excretion during sleep). Lesser pathways are sweat and faeces (particularly when a capsule is used).
Breast milk can contain significant amounts of radioiodine, and patients who are breast feeding must cease feeding before their therapy.
The proportion of each form of contamination (apart from urine) will vary widely, so it is best to assume that all are present, until proved otherwise. The excretion phase may not be complete before discharge, or will not have begun if the patient leaves immediately after administration of the radiopharmaceutical.
Post-discharge issues
Unless there is active excretion at time of discharge, the radiation safety problem is confined to external radiation. As the radioiodine which remains is mainly localised in thyroid tissue, overwhelmingly in the neck (unless there are significant metastases), there can be significant levels of radiation at short distances.
If there is still excretion taking place, contamination of household objects, other persons, and the toilet may occur.
Advice to patients and families
Contamination
Even if excretion is still occurring at discharge, it is normally quite low in activity. Urinary excretion is normally promoted in hospital by frequent fluid intake, and this should be continued after discharge for a few days. Patients should be advised to flush the toilet twice after use, and males should avoid 'splashing' (sitting down to urinate is recommended). Patients should wash their hands frequently. Sharing food or eating utensils should be avoided. Daily showering will remove sweat. Clothing should be separately laundered. Breast feeding must cease before radioiodine therapy, and not be resumed under any circumstances.
If the patient is discharged immediately after administration,of the radiopharmaceutical, these precautions must be followed for at least a few days. Importantly, vomiting within 4-6 hours after oral administration of radioiodine in any form (i.e. before extraction from the gut is complete) will be a significant source of contamination. A patient who vomits should do so into a container or directly into the toilet, which must be flushed clean. The nuclear medicine department must be notified, as the effectiveness of the therapy will be diminished.
External radiation
In most cases, this is the most important safety issue. Once excretion is effectively complete, the external radiation will decline only with the effective half-life, which for iodine-131 is about 8 days. Family members, especially the spouse, and the public may potentially all receive significant doses unless some basic precautions are followed, all for about 5-7 days unless otherwise specified. Avoid public transport, or limit journey time to less than two hours. Try to sit one meter or more from other passengers. Similarly, social events should be avoided.
At home, avoid prolonged physical contact. A simple rule is to maintain at least an arm’s length distance, and preferably one meter, for short periods only. For extended periods, two meters.
Avoid all contact with children or pregnant women. If the patient has young children, who will demand physical contact, this should be allowed for very short periods (a few minutes) only. Ideally, the patient’s children should be accommodated elsewhere for a week.
Return to work should be postponed for at least two days, possibly longer.
There are cases where the contamination and external radiation measures can be modified, e.g. where the patient is elderly, and the other home occupant(s) are as well. Then the radiation risk is low, and only (contamination prevention) measures which are easy to take are necessary. The nuclear medicine staff where the therapy is performed will be able to give more specific advice.
Emergencies
In a case of patient illness or accident, requiring attendance by a doctor or at a hospital, the medical staff involved must be notified of the therapy, and the date, radionuclide and activity involved. As mentioned above, the nuclear medicine department must be notified of vomiting within 4-6 hours of the therapy.
Primary hepatocellular carcinoma (HCC) is the most common primary liver malignancy and among the 10 most common tumours in the world. Chronic infection with the hepatitis B or C virus appears to be the most important risk factor for HCC. One approach to treatment of primary hepatocellular carcinoma (HCC) is intra-arterial injection of iodine-131 lipiodol. This therapy is used in two clinical scenarios: therapy for inoperable HCC; and as adjuvant therapy, following HCC resection.
Radionuclide and form
Iodine-131 lipiodol (ethiodized oil), activity up to 2 GBq, typically 1 GBq.
Methodology
Selective hepatic arterial injection, sometimes more than one site. Around 70-90% of administered activity is trapped in the liver. 10-20% may be taken up in the lungs due to arteriovenous shunting, increasing with time as uptake in the liver may be partly released to the general circulation, mostly as free iodide.
Excretion
Unbound activity (i.e. not in liver or lungs) is predominantly excreted via urine. This may be up to 30-50% at 8 days. Very small faecal excretion (<3%). Very low or nil excretion by other pathways.
External radiation
Due to the high uptake within liver and lungs, the external radiation level is the prime determinant of discharge time.
Post-discharge issues
Urinary excretion is slower than for iodine-131 iodide, so toilet precautions must be maintained for one week after administration.
Advice to patients and families
With the exception of those measures relating to sweat/saliva, similar to that for iodine-131 iodide therapy.
Iodine-131 MIBG is used to treat neuroendocrine tumours, which are relatively rare in adults and mainly consist of phaeochromocytomas, carcinoid tumours, paragangliomas, neuroblastomas and medullary thyroid cancer. In the paediatric population, neuroblastoma is the most common solid tumour in infants younger than one year.
Radionuclide and form
Iodine-131 MIBG (metaiodobenzylguanidine), 4–11 GBq, although a typical dose is 5 GBq. Lower activities (about 600 MBq) are often used to detect the distribution of disease prior to therapy, and its uptake of MIBG.
Methodology
Administration is by slow injection of a volume of about 50 ml over a period of about one hour. Thyroid uptake of any free iodine is blocked by administration of potassium iodide (Lugol’s iodine) for three days prior to the therapy, and for at least one day post therapy.
Excretion
Urinary excretion can occur in the first five days or so, and other pathways may be present. The same information applies as for iodine-131 therapy for thyroid disease. Vomiting, however, is not a radiation safety issue.
Post-discharge issues
As for iodine –131 therapy for thyroid disease.
Advice to patients and families
As for iodine –131 therapy for thyroid disease.
» Phosphorous-32 therapy for myeloproliferative disease
Phosphorous-32 has been an accepted treatment for refractory myeloproliferative disease for over 30 years. Myeloproliferative diseases include polycythaemia rubra vera and essential thrombocythaemia and are a family of disorders characterized by increased blood cell production. The use of phosphorous-32 for treatment of these diseases is declining with the development of newer chemotherapeutic agents. It is generally reserved for patients over the age of 70.
Radionuclide and form
Phosphorous-32 as sodium phosphate. Typical activity is 70–180 MBq.
Methodology
Intravenous injection.
Excretion
Urinary excretion in the 48 hours following administration.
External radiation
Due to phosphorous-32 being a pure beta emitter, the external radiation level is low, and due to bremsstrahlung.
Post-discharge issues
The main issue is urinary excretion, which requires care as phosphorous-32 is difficult to remove from the skin, and can migrate through the skin.
Advice to patients and families
Toilet practices as for iodine-131 iodide therapy should be observed. As external radiation is not significant, no other precautions are required.
Emergencies
In a case of patient illness or accident requiring attendance at a hospital, the medical staff involved must be notified of the therapy, and the date, radionuclide and activity involved.
» Rhenium-188 therapy for palliation of bone pain
Control of pain in patients with advanced malignancies due to bone metastases poses a challenge. Rhenium-188-hydroxyethylidine diphosphonate (188Re-HEDP) is a novel and attractive radiopharmaceutical that localizes in areas of osseous metastases and emits beta particles with energy sufficient to be therapeutically useful. Prompt and significant relief of bone pain occurs in large number of patients with no significant side-effects or hematopoietic toxicity. Many patients are able to discontinue analgesics after treatment.
Radionuclide and form
Re-188 HEDP (hydroxyethylidine diphosphonate) typical activity 1.2 to 4 GBq. Due to the short half-life (16.9 hours) Re-188 is produced using a W-188/Re-188 generator.
Methodology
Intravenous injection.
Excretion
Urinary excretion of unbound material in the early period following administration. Because of the high beta energy, contamination precautions should be observed.
External radiation
Re-188 is a beta and gamma emitter. The gamma emission is at a relatively low level, and the half-life is short.
Post-discharge issues
The main issue is urinary excretion, especially for patients who are incontinent. If administered as outpatient therapy, it may be advisable to keep the patient in hospital for at least one bladder voiding following administration of the radiopharmaceutical. The gamma emission from Re-188 is not a particular concern, especially given the short half-life.
Advice to patients and families
Toilet practices as for iodine-131 iodide therapy should be observed. As external radiation is not significant, no other precautions are required. Linen or clothing contaminated with urine in the first few days must be separately washed, preferably twice, or with an extra rinse cycle.
Emergencies
In a case of patient illness or an accident requiring attendance at a hospital, the medical staff involved must be notified of the therapy, and the date, radionuclide and activity involved.
» Samarium-153 therapy for palliation of bone pain
Skeletal metastases occur from a wide variety of malignancies. The patient with bony metastases presents a series of problems. These patients often have remarkably decreased quality of life because of the pain and the morbidity associated with various drugs used to treat pain. Samarium-153 EDTMP has recently been introduced, which localizes by a mechanism similar to that for strontium-89, i.e. substitution for calcium in the bone matrix.
Radionuclide and form
Samarium-153 EDTMP, typical activity 1 GBq.
Methodology
Intravenous injection.
Excretion
Urinary excretion of unbound material in the 48 hours following administration.
External radiation
Samarium-153 is a beta and gamma emitter. The gamma emission is at a relatively low level, and the half-life is short (46.3 hours).
Post-discharge issues
The main issue is urinary excretion, especially for patients who are incontinent. If administered as outpatient therapy, it may be advisable to keep the patient in hospital for at least one bladder voiding following administration of the radiopharmaceutical. The gamma emission from samarium-153 is not a particular concern, but pregnant women and children should remain at arm’s length for two days.
Advice to patients and families
Toilet practices as for iodine-131 iodide therapy should be observed. As external radiation is not significant, no other precautions are required. Linen or clothing contaminated with urine in the first few days must be separately washed, preferably twice, or with an extra rinse cycle.
Emergencies
In a case of patient illness or an accident requiring attendance at a hospital, the medical staff involved must be notified of the therapy, and the date, radionuclide and activity involved.
» Strontium-89 therapy for palliation of bone pain
Skeletal metastases occur from a wide variety of malignancies. The patient with bony metastases presents a series of problems. These patients often have remarkably decreased quality of life because of the pain and the morbidity associated with various drugs used to treat pain. The most widely used radioactive therapeutic agent at the present time is strontium-89 chloride. Strontium substitutes for calcium in the bone matrix as an excellent analogue.
Radionuclide and form
Strontium-89 chloride, typical activity is 150 MBq.
Methodology
Intravenous injection.
Excretion
Urinary excretion of unbound material in the 48 hours following administration.
External radiation
Strontium-89 is a pure beta emitter, and the external radiation level is low, and due to bremsstrahlung.
Post-discharge issues
The main issue is the urinary excretion, especially for patients who are incontinent. If administered as outpatient therapy, it may be advisable to keep the patient in hospital for at least one, preferably two, bladder voidings following administration of the radiopharmaceutical.
Advice to patients and families
Toilet practices as for iodine-131 iodide therapy should be observed. As external radiation is not significant, no other precautions are required. Linen or clothing contaminated with urine in the first few days must be separately washed, preferably twice, or with an extra rinse cycle.
Emergencies
In a case of patient illness or an accident requiring attendance at a hospital, the medical staff involved must be notified of the therapy, and the date, radionuclide and activity involved.
Selective internal radiation therapy is a technique which involves embolizing radioactive yttrium-90 microspheres into the arterial supply of the liver as an alternative to iodine-131 lipiodol. It has many similarities to lipiodol therapy; however, it can be used for treatment of both primary and secondary hepatic tumours. Most commonly, it is used in metastatic colorectal carcinoma but has been given in rarer malignancies, such as metastatic neuroendocrine tumours with good effect. The therapeutic effect is thought to be due to not only the beta radiation, but also to the occlusive effect on the hepatic arterial tree.
Radionuclide and form
Yttrium-90 resin or glass microspheres. Activity is up to 3 GBq.
Methodology
Introduced by selective arterial injection.
Excretion
Minimal or none.
External radiation
Due to yttrium-90 being a pure beta emitter, the external radiation level is low, and due to bremsstrahlung.
Post-discharge issues
The low level of external radiation, and the short half-life (2.7 days), means that there are no post-discharge safety issues.
Advice to patients and families
None necessary.
Emergencies
In a case of patient illness or an accident requiring attendance at a hospital, the medical staff involved must be notified of the therapy, and the date, radionuclide and activity involved.
» Radiation synovectomy with yttrium-90 silicate
Inflammatory joint diseases are common. Many of these diseases may be treated by synovectomy to stop disease progression and to improve joint function. The intra-articular injection of yttrium-90 silicate for the knee joint, rhenium-186 sulphur colloid for middle-sized joints and erbium-169 citrate colloid for small joints results in an improvement in symptoms and function in about 60-80% of treated patients.
Radionuclide and form
Yttrium-90 silicate, typical activity is 185 MBq.
Methodology
Intra-articular injection.
Excretion
Effectively none. Leakage from the joint into the circulation would be the only source.
External radiation
Yttrium-90 is a pure beta emitter, and the external radiation level is low, and due to bremsstrahlung.
Post-discharge issues
None.
Advice to patients and families
As external radiation is not significant, no precautions are required.
Emergencies
In a case of patient illness or an accident requiring attendance at a hospital, the medical staff involved must be notified of the therapy, and the date, radionuclide and activity involved.