Radiopharmaceutical Therapy for Palliation of Bone Pain from Osseous Metastases*

Neeta Pandit-Taskar, MD; Maria Batraki, BS; and Chaitanya R. Divgi, MD

Nuclear Medicine Service, Memorial Sloan-Kettering Cancer Center, New York, New York

Key Words: radiopharmaceutical therapy; bone-seeking radio- Bone metastasis occurs as a result of a complex pathophysio- pharmaceuticals; bone pain; osseous metastases logic process between host and tumor cells leading to cellular J Nucl Med 2004; 45:1358–1365 invasion, migration adhesion, and stimulation of osteoclastic and osteoblastic activity. The process is mediated by parathyroid hormones, cytokines, and tumor-derived factors. Several sequelae occur as a result of osseous metastases and resulting one metastasis is a major complication of several solid bone pain can lead to significant debilitation. Pain associated B with osseous metastasis is thought to be distinct from neuro- cancers; the prostate, breast, lung, kidney, and thyroid are pathic or inflammatory pain. Several mechanisms—such as in- cancers most associated with bone pain (most often, breast vasion of tumor cells, spinal cord astrogliosis, and sensitization and prostate). Although bone metastases are often clinically of nervous system—have been postulated to cause pain. Phar- silent, they can lead to serious sequelae, such as pain, maceutical therapy of bone pain includes nonsteroidal analge- fractures, and hypercalcemia. These complications often sics and opiates. These drugs are associated with side effects, reduce performance status and decrease the quality of life. and tolerance to these agents necessitates treatment with other Bone pain due to metastasis is often considered a unique modalities. Bisphosphonates act by inhibiting osteoclast-medi- type of pain. It is initially a dull or aching pain, worse at ated resorption and have been increasingly used in treatment of night, that improves with physical activity (1). If pain in- painful bone metastasis. While external beam radiation therapy remains the mainstay of pain palliation of solitary lesions, bone- creases with physical activity, the risk of imminent fracture seeking radiopharmaceuticals have entered the therapeutic ar- is increased. mamentarium for the treatment of multiple painful osseous le- The pathophysiology of bone metastasis and related com- sions. 32P has been used for Ͼ3 decades in the treatment of plications is complex. Normal bone undergoes continuous multiple osseous metastases. The myelosuppression caused by remodeling that is essential to maintain mechanical func- this agent has led to the development of other bone-seeking tion. The process is performed by a multicellular unit radiopharmaceuticals, including 89SrCl, 153Sm-ethylenediamine- formed by 2 different cell types, osteoclasts and osteoblasts. 153 179m tetramethylene phosphonic acid ( Sm-EDTMP), SnCl, and Osteoclasts resorb bone, whereas osteoblasts replace bone 166 Ho-Labeled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetra- (2). Systemic factors—such as the parathyroid hormone, methylenephosphonate (166Ho-DOTMP). 89Sr is a bone-seeking radionuclide, whereas 153Sm-EDTMP is a bone-seeking tetra- local osteoclast-activating cytokines, and growth factors— phosphonate; both have been approved by the Food and Drug contribute to the process (3). During bone resorption, Administration for the treatment of painful osseous metastases. growth factors and mineral ions are released from the bone While both agents have been shown to have efficacy in the matrix. When bone metastases occurs, a cycle of signaling treatment of painful osseous metastases from prostate cancer, takes place that results in increased osteolytic activity. Tu- they may also have utility in the treatment of painful osseous mor-derived factors stimulate osteoclast-mediated bone re- metastases from breast cancer and perhaps from non–small cell sorption, whereas the growth factors released from the bone lung cancer. This article illustrates the salient features of these matrix stimulate the tumor cells to grow and secrete addi- radiopharmaceuticals, including the approved dose, method of tional cytokines. This leads to osteopenia and increased risk administration, and indications for use. We conclude with rec- of developing fractures and, when lesions are in vertebrae, ommended guidelines for therapy and follow-up. spinal cord compression. The calcium released from the bone matrix in the course of this process can lead to the hypercalcemia of malignancy (HCM), a serious metabolic condition. Received Apr. 15, 2004; accepted Apr. 15, 2004. For correspondence or reprints contact: Neeta Pandit-Taskar, MD, Nuclear Skeletal metastasis is a multifactorial process in which Medicine Service, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., several biologic processes play a role leading to interaction New York, NY 10021. E-mail: [email protected] between host and tumor cells. Cellular invasion and migra- *NOTE: FOR CE CREDIT, YOU CAN ACCESS THIS ACTIVITY THROUGH THE SNM WEB SITE (http://www.snm.org/ce_online) THROUGH AUGUST tion, cell matrix adhesion or cell-to-cell adhesions, interac- 2005. tion with endothelial cells, regulation of growth factor, and

1358 THE JOURNAL OF NUCLEAR MEDICINE • Vol. 45 • No. 8 • August 2004 stimulation of osteoclasts and osteoblasts are thought to cause pain in cancer patients. It is also thought that tumor contribute to development of skeletal metastasis. growth may entrap and injure nerves, causing neuropathic Cadtherins, integrins, imuunoglobulins, selectins, and CD44 pain (8–10). are some of the molecules implicated in loss of cellular Management of bone pain includes analgesia, radiation, adhesion that causes cell matrix detachment, invasion, and radiofrequency (RF) ablation, hormones, chemotherapy, migration. Several isoforms of CD44, an adhesion molecule and surgery. Localized sites of involvement can be treated that binds hyaluronate, have been associated with lymphatic with surgery, RF ablation, or external beam radiation, spread of the tumors and are expressed in breast and colon whereas radiopharmaceuticals, hormones, and chemother- cancers. P selectins bind to a wide range of carcinoma cells, apy are used to treat more diffuse bone involvement. including breast, colon, and lung. Interaction with the en- Control of bone pain usually begins with analgesic med- dothelial cells leads to local arrest or further migration of ications used in a 3-step approach. Nonsteroidal antiinflam- the tumor cells. Platelet fibrin thrombi and inflammatory matory drugs (NSAIDs), including aspirin, ibuprofen, and cytokines lead to adhesions and arrest of the tumor cells, naproxen, are used to relieve mild to moderate pain initially. whereas chemotactic factors lead to increased mobility of With persistent or increased pain while on NSAIDs, treat- tumor cells. Invasiveness is mediated by several enzyme ment progresses to the second step, which utilizes weak systems, including serine proteases, of which matrix metal- opioids, such as codeine or hydrocodone, changing to loproteins and urokinase plasminogen activation system are higher doses or more potent opioids (step 3), such as mor- thought to be most important. Cellular motility is critical for phine, hydromorphone, or fentanyl, if the pain persists or tumor cells to develop distant metastasis. Motility is medi- becomes more severe. The more potent narcotic agents have ated by several factors, including: growth factors, hyaluro- significant side effects, including constipation, limitations in nians, components of matrix, and host- or tumor-secreted mental and physical status, and addiction. Lethargy and factors. Cytokinins such as autotoxin and hepatocyte growth constipation are particularly common symptoms. Increased factor are also implicated in inducing cell motility (4–7). doses also increase the cost significantly when used on a Pain from bone metastasis is of variable intensity and long-term basis. To limit the dose of these medications, intermittent at onset but progresses to continuous low level radiation therapy and surgery are used for the treatment of pain with episodes of breakthrough pain, which later be- localized bone metastases. Some patients with extensive comes chronic pain. Mechanical allodynia, in which normal disease in a portion of the body are candidates for hemibody nonpainful activity such as coughing and gentle limb move- irradiation. Hemibody radiation provides relief from pain ments can also be perceived as painful, can occur leading to associated with extensive bone involvement, but it is asso- significant limitation of activity. Bone pain is thought to be ciated with a high incidence of side effects (11). Bone- distinct from neuropathic or inflammatory pain, where there seeking radionuclides are therefore preferred for widespread is upregulation of the glial fibrillary acidic protein in the painful bone metastasis (12). spinal cord indicating astrogliosis. The exact mechanism of cancer pain is unknown and it is postulated that the pain BISPHOSPHONATES may be due to the presence of tumor in the bone. Treatment Bisphosphonates (Fig. 1) inhibit osteoclast-mediated with bisphosphonates supports the thought that osteolysis bone resorption by binding to bone mineral, interfering with leads to bone pain, which is linked to the number and extent osteoclast activation. These agents also promote repair by of osteoclastic activity. Bone cancer pain is also thought to stimulating osteoblast differentiation and bone formation. occur due to sensitization of the nervous system. Sensory As a result, these agents are playing an increasing role in the information from peripheral tissues is transmitted to the treatment of painful bone metastases. spinal cord and brain by primary afferent sensory neurons, Bisphosphonates are used in the treatment of benign nociceptors that detect stimuli that are perceived as harmful conditions, such as osteoporosis; in malignancies with os- and convert into electrochemical signals that are transmitted teoblastic and osteolytic bone metastases as well as HCM to the central nervous system. Tumors secrete a variety of (13,14). The use of bisphosphonates has made a significant factors that sensitize or directly excite primary afferent change in the therapeutic approach to management of bone neurons, causing the sensation of pain. Receptors for many metastasis and pain prevention in breast cancer and multiple of these factors are expressed by primary afferent neurons. myeloma (15). Bisphosphonates reduce skeletal complica- Peripheral sensitization leads to increased release of sub- tions (16): delay progression of existing bone metastases stance P from nociceptors, even with minor stimulation. Sensitization also occurs centrally in the dorsal horn of the spinal cord, which leads to allodynia and hyperalgesia. The spinal cord may show marked astrocytosis, increased ex- pression of c-Fos (a general marker of neuronal activity), and a peptide—dynorphin. Other factors that may contribute to the activation of sensory neurons, is the lower intra- FIGURE 1. Structure of bis- cellular and extracellular pH of solid tumors, which can also phosphonate.

PALLIATION OF PAIN FROM OSSEOUS METASTASES ¥ Pandit-Taskar et al. 1359 and reduce the development of new lesions in patients with In about 80% of patients with local pain, a single dose of breast cancer and multiple myeloma (17,18). radiation will achieve pain relief within 4Ð6 wk. If a lesion Pamidronate, zoledronate, and clodronate are some of the recurs at that site, retreatment is effective if subradical doses bisphosphonates that have been used clinically. Pamidr- were used (34–36). Wide-field external beam treatment onate is a second-generation bisphosphonate that is effec- aimed to cover areas roughly equivalent to the half-body tive in patients with multiple myeloma or breast cancer, who above or below the diaphragm depending on the sites of primarily have osteolytic metastases (19,20), and is shown pain may be given in those with widespread disease or to reduce skeletal complication and morbidity in patients where systemic treatment has failed or is inappropriate. with breast cancer (20–22). Zoledronic acid is a newer Treatment is delivered as single doses of 6 Gy to the upper nitrogen-containing bisphosphonate that has been evaluated hemibody, which is limited by lung tolerance, and 8 Gy to in bone metastases from a variety of cancers. Zoledronic the lower hemibody (37). Sequential hemibody radiother- acid was shown to be as effective as pamidronate in reduc- apy, allowing 4Ð6 wk between each treatment, is given to ing skeletal complications (23) but was superior in treating achieve coverage of the whole skeleton with external beam hypercalcemia (24). In breast cancer patients, bisphospho- radiotherapy. The interval between treatments is useful for nate therapy is recommended for patients with radiographic bone marrow regeneration. After lower hemibody treat- evidence of bone destruction but is not recommended for ment, short-lived and self-limiting nausea and gastrointes- treatment based an abnormal bone scan alone (25). This tinal upset are common; in upper hemibody treatment, therapy also reduces skeletal-related events in hormone- pneumonitis is common if tolerance doses are exceeded. refractory prostate cancer (26), nonÐsmall cell lung cancer, Symptomatic bone marrow depression may also occur and and urologic malignancies (27,28). transfusion is often required to maintain the hemoglobin in There has been concern regarding the efficacy of bone the early weeks after treatment (38), though life-threatening scanning in patients who were treated with bisphosphonates complications such as neutropenia or thrombocytopenia are since methylene diphosphonate (MDP) is similar to the unusual. bisphosphonates. The literature is controversial, suggesting that the timing of the bone scan vis-a`-vis the last dose of RADIOPHARMACEUTICAL THERAPY bisphosphonate is critical, though this has not been borne Since multiple sites of osseous metastases are common out by studies with etidronate and alendronate (29–31). and some patients have multifocal bone pain, systemic targeted treatment of the skeletal metastatic sites offers the RADIATION THERAPY potential of pain relief with minimal side effects. Radio- External beam radiation therapy can often produce pain pharmaceuticals developed for the treatment of painful bone 32 89 186 relief within 48 h of the start of therapy. External beam metastases use the following radionuclides: P, Sr, Re, 188 153 177 therapy is most effective when the disease is localized, Re, Sm, and Lu (Table 1). All agents have advan- allowing the highest dose to be delivered to the lesion. If tages and side effects. The agents differ in terms of efficacy; multiple lesions at multiple sites require therapy, side ef- duration of pain palliation; tumoricidal effects; ability to fects—particularly bone marrow suppression—limit the repeat treatments; toxicity, and expense. Most studies with dose that can be delivered. Hemibody radiation therapy has these agents have been conducted in prostate and breast been used in patients with widespread lesions and pain but cancer patients. can lead to significant toxicity, including alopecia and radiation pneumonitis if the upper body is treated; or nausea, MECHANISM OF ACTION vomiting, and diarrhea if the lower body is treated. Myelo- The sources of radiation within bone differ with the suppression can also occur especially in patients treated radiopharmaceutical used: The metallic chelated radiotrac- with whole-body radiation. ers tend to chemically absorb to the trabecular surface, The mechanism of pain relief after radiation therapy is whereas 32P and 89Sr (as the chloride) distribute more widely not known. Radiation causes a reduction in the number of throughout bone. Due to the heterogeneity of radiopharma- viable tumor cells that may result in shrinkage of the tumor. ceutical uptake, spicule thickening, and tumor and marrow Removal of the tumor from bone then enables osteoblastic distribution, there is variation in dosimetry (39). repair, restoring integrity of the damaged bone. However, certain features—especially the lack of a doseÐresponse 32P relationship and the rapid pain relief, which may be seen 32P is a reactor-produced, pure ␤-emitting radionuclide especially after systemic radiation (within 24Ð48hinupto with a physical half-life of 14.3 d. The maximum and mean 25% of patients)—make it unlikely that tumor shrinkage ␤-particle energies are 1.71 and 0.695 MeV, respectively, itself is responsible for the pain relief (32). It has also been with the mean and maximum particle range in tissue of 3 suggested that radiation may have an analgesic effect and 8 mm, respectively. Oral and injectable 32P (usually the through osteoclast inhibition, which provides an insight to injectable sodium orthophosphate) was introduced for treat- bisphosphonate activity (33). ment of metastatic bone pain Ͼ50 y ago. 32P is incorporated

1360 THE JOURNAL OF NUCLEAR MEDICINE ¥ Vol. 45 ¥ No. 8 ¥ August 2004 TABLE 1 Radiopharmaceuticals

Half-life ␤-Energy (MeV) ␥-Energy Soft-tissue range (mm) Isotope Compound (d) [maximum/mean] (MeV) [%] [maximum/minimum]

32P 32P 14.3 1.71/0.695 — 8/3 89Sr 89Sr/Cl 50.5 1.46/0.58 0.91 (0.01) 2.4 186Re 186Re-HEDP 3.7 1.07/0.349 0.137 (9) 2.4 188Re 188Re-HEDP 0.7 2.12 — 3 153Sm 153Sm-EDTMP 1.9 0.81/0.23 0.103 (28) 0.6 177Lu 177Lu-EDTMP 6.7 0.497 0.208 (11) — 117mSn 117mSn-DTPA 13.6 ——Emits conversion electrons: 0.3/0.2

into the hydroxyapatite molecule present in large amounts to 84% (47). The onset of pain relief is generally within in most osseous metastases. The likely mechanism of action 7Ð21 d, with a mean duration of relief of about 6 mo. is DNA damage from decay to 32S, with subsequent cell Transient increased bone pain (painful flare) may occur in death, as well as damage to cells producing pain modula- the first 2Ð3 d after treatment. This is usually mild, self- tors—for example, lymphocytes that produce lymphokines. limited, and controlled with analgesics. A flare usually 32P as sodium orthophosphate was one of the first radio- heralds a good treatment response. Patients can be retreated pharmaceuticals used to reduce pain from bone metastases after 90 d, though multiple therapies may lead to greater (40) and the most widely used radiotracer until the 1980s marrow toxicity. There is a doseÐresponse relationship for (41). Its uptake in malignant tissue was demonstrated by complete relief of pain (though not for partial pain relief) Lawrence et al. (42). Earlier studies used testosterone and (48). Several studies have demonstrated no significant dif- androgen stimulation for 32P bone metastasis therapy (43– ferences between response to 89Sr and response to local or 45). The response rates were between 59% and 93% for hemibody radiation (49,50). Concurrently administered che- prostate cancer and between 52% and 94% for breast can- motherapy is effective in enhancing pain relief and delaying cer, with overall response rates of 77% and 84%. No doseÐ the onset of new painful metastases (51). However, com- response relationship was seen. Pain palliation occurred bining 89Sr with chemotherapy does not increase the overall within 14 d, with a range of 2 d to 4 wk. A major problem pain relief response rates (complete plus partial response of with 32P therapy is the occurrence of toxicity, including 55%Ð80%). Although the agent is useful for osseous pain myelosuppression and pancytopenia. Additional concerns palliation, there is no survival benefit, even when a dose of include the very high ␤-energy and low lesion-to-normal 399.6 MBq (10.8 mCi) is used (49,52). However, in patients bone ratio. Pancytopenia occurs around 4Ð5 wk, with re- with androgen-independent prostate cancer and severe bone covery by 6Ð7 wk, and is dose dependent. However, this is pain (53), combined treatment with 89Sr and doxorubicin not found to be clinically significant with either a single resulted in a mean survival of 28 mo compared with 17 mo dose or even multiple doses up to 444 MBq (12 mCi). Acute for patients treated with doxorubicin alone. The use of 89Sr leukemias have been reported with use of 32P in polycythe- can help reduce the lifetime health-care costs by decreasing mia vera; however, grade 4 leukopenia and thrombocytope- both the need for radiotherapy and the need for narcotics nia are quite rare (41). and hospitalization (54,55). 89SrCl 153Sm Strontium is an element that behaves biologically like 153Sm, a nuclide with a physical half-life of 1.9 d, decays calcium. It localizes in bone primarily in areas of osteoblas- by ␤-emission. The ␤-particle has a maximum energy of tic activity. 89Sr has a physical half-life of 50.5 d and emits 0.81 MeV, a mean energy of 0.23 MeV, and an average a ␤-particle with a maximum energy of 1.46 MeV and an soft-tissue range of 0.6 mm. The ␤-ray is accompanied by a average soft-tissue range of 2.4 mm. The usual therapeutic 103-keV ␥-ray, which is 28% abundant. 153Sm is complexed dose is 148 MBq (4 mCi). with ethylenediaminetetramethylene phosphonic acid to After intravenous administration, 89Sr is concentrated in form 153Sm-EDTMP. This phosphonate complex concen- bone in proportion to osteoblastic activity. Of the 89Sr that trates in the skeleton, in proportion to osteoblastic activity. is not concentrated in bone, about 80% is excreted through After intravenous injection, Ͻ1% remains in the blood at the kidneys and about 20% through the gastrointestinal 5 h. About 65% of the dose remains in the skeleton. The system. Although the biologic half-life is 4Ð5 d, about 20% urinary excretion is nearly complete by6h(56). The is retained in the body after 90 d (46). distribution of 153Sm-EDTMP is identical to that of bone- 89Sr therapy can relieve bone pain for up to 14 mo and is seeking radiopharmaceuticals such as 99mTc-MDP (99mTc- recommended for use in patients with moderate pain and a methylene diphosphonate) (57) (Fig. 2). 153Sm-EDTMP is reasonable life expectancy. Response rates range from 60% usually administered at a dose of 37 MBq/kg (1 mCi/kg).

PALLIATION OF PAIN FROM OSSEOUS METASTASES ¥ Pandit-Taskar et al. 1361 and efficacy of use of 186Re-HEDP in bone pain palliation. The maximum tolerated administered activity of 186Re- HEDP in patients with metastatic breast cancer was found to be 2,405 MBq (65 mCi) with thrombocytopenia as dose- limiting toxicity (63), and a response rate of 77% has been reported (64). Its role in androgen-independent prostate cancer and multiple other cancers has also been studied with reported response rates of about 50%Ð100% in various cancers (65,66). For a variety of reasons, however, the agent is not available for use in the United States. 188Re is an isotope of 186Re and is also been used for bone pain palliation. It is inexpensive, as it may be “milked” on FIGURE 2. Targeting of bone metastases with 153Sm-EDTMP 188 188 in patient with prostate cancer. ANT ϭ anterior; POST ϭ pos- demand from a W/ Re generator, and a kit is available terior. Arrow indicates uptake in pubic bone. for attaching it to HEDP. 188Re-(Sn)HEDP has similar biodistribution and radiation dosimetry characteristics as 186Re- (Sn)HEDP and appears to result in similar benefits and toxicities in patients with skeletal metastases. Dosimetric An initial dose-escalation study demonstrated dose-limiting calculations asserted safe, same-day outpatient therapy to be myelotoxicity, with a maximum tolerated dose of 37 feasible with 188Re-(Sn)HEDP (67). This has mainly been MBq/kg (1 mCi/kg) (58). Platelet nadir occurred between investigated for use in developing countries. It offers the days 16 and 45 (median, 28 d). Pain palliation occurs in possibility of repeated therapy without additional costs. The 62%Ð74% of patients (56,59,60) with better overall re- high energy of this ␤-emitter, with a maximal energy of sponses at higher doses. Pretreatment platelet count, tumor 2.12 MeV, has the potential of killing tumor cells. There are type, prior hormonal therapy, and percentage of 153Sm- limited data on the use of this agent. An initial study EDTMP uptake had more impact on myelotoxicity than the demonstrated pain palliation in 60%Ð75% of prostate cancer administered activity. Patients with extensive metastases patients receiving a dose of Ն2.6 GBq (68). Recently, the were more likely to have myelotoxicity, probably due to a effectiveness of repeated therapy using 188Re-HEDP has fragile marrow. Bone marrow suppression was generally been demonstrated in 64 patients with progressive, hor- mild, reversible, and not associated with grade 4 toxicity. mone-resistant prostate cancer (69). Platelets and white blood cells reached nadir at 3 or 4 wk with both doses and recovered by 8 wk (61). A trend toward 117mSn-Pentetate improved survival was also seen (59). The chelate 117mSn-diethylenetriaminepentaacetic acid 153Sm is the most widely used pain palliation radiophar- (117mSn-DTPA) is an experimental radiopharmaceutical un- maceutical agent in the United States. Its ease of use, the dergoing evaluation for treatment of painful bone metasta- ability to image its distribution, and its clinical results ses. 117mSn, a nuclide with a physical half-life of 13.6 d, (including the ability to titrate the amount based on body decays by isomeric transition with emission of the dominant weight) make it attractive, while issues with availability, ␥-ray at 156 keV. The ␥-ray undergoes conversion and it is radiation safety, and potential irreversible myelosuppres- the conversion electrons that have the therapeutic potential. sion limit wider use. The energetic conversion electrons have a very short range in soft tissue (0.2Ϫ0.3 mm), which may explain the low Rhenium Isotopes incidence of myelosuppression seen with 117mSn-pentetate. 186Re-Labeled 1,1-hydroxyethylidene diphosphonate 117mSn is injected as the pentetate (DTPA) chelate and has (186Re-HEDP/186Re-(Sn)HEDP or etidronate) and 188Re are no affinity for hydroxyapatite. The mechanism of localiza- investigational radiopharmaceuticals for bone pain palliation is postulated as precipitation of stannous oxide on bone tion. 186Re has a physical half-life of 3.7 d and emits a surfaces or by a hydrolysis reaction with hydroxyapatite. In ␤-particle with a maximum energy of 1.07 MeV, a mean reported studies, the pain palliation rate is approximately energy of 0.349 MeV, and an average soft-tissue range of 75%. There is no doseÐresponse relationship; the onset of 1.1 mm. A study by Sciuto et al. with 186Re-HEDP showed pain relief is also much earlier than that with the other overall pain palliation of 92% in breast cancer patients (47). agents described. At doses of Ͼ444 MBq (Ͼ12 mCi) (per Pain relief was established early and the tumor-to-bone 70 kg body weight), pain palliation has been noted as early marrow absorbed dose ratio was 14:1, suggesting its clinical as Ͻ1 wk after treatment (70). relevance in patients with more compromised bone marrow reserve. Typical marrow recovery times range from 4 to 6 wk. Other reported side effects are mild pain flare phenom- PATIENT IDENTIFICATION AND REFERRAL enon (6.5%), occurring in the first week after treatment and Patients referred for bone pain palliation therapy are most lasting 2Ð4d(62). Several initial studies reported the safety commonly breast and prostate cancer patients, referred for

1362 THE JOURNAL OF NUCLEAR MEDICINE ¥ Vol. 45 ¥ No. 8 ¥ August 2004 TABLE 2 Common Indications and Contraindications

Indications Contraindications

Multiple painful osseous metastases Pregnancy; breastfeeding; women of child-bearing age Skeletal metastasis involving Ͼ1 site that are positive Acute or chronic renal failure (increased tracer uptake) on bone scintigraphy Acute spinal cord suppression: needs external radiation therapy Hemoglobin Ͻ 90 g ⅐ LϪ1 Total white cell count Ͻ 3.5 ϫ 109 LϪ1 Absolute neutrophil count Ͻ 1.5 ϫ 109 LϪ1 Platelets Ͻ 60 ϫ 109 LϪ1 Glomerular filtration rate Ͻ 30 mL/min radiopharmaceutical treatment by the medical oncologists. 89Sr is used, a fixed dose of 148 MBq (4 mCi) is usually Before treatment it is mandatory to check the complete used. If 159Sm is used, the patient is weighed, and 37 blood count, total leukocyte count, and platelet count (Ta- MBq/kg (1 mCi/kg) is administered. The dose is adminis- bles 2 and 3). Since the blood counts can change dramati- tered by an attending physician. The tracer is injected as a cally in these patients, especially if they are receiving other slow intravenous injection over a period of 1Ð2 min and chemotherapy or radiotherapy, the blood counts should be flushed with 10Ð20 mL of saline. A note is placed in the performed within a week before therapy. Patients with my- patient’s record describing the administration. The radiation elosuppression should be evaluated carefully to determine if safety officer is informed and present during the adminis- the benefits of treatment outweigh the risks of worsening the tration. If the patient is treated with samarium, images are myelosuppression. usually recorded at 24 h to compare with the diagnostic A detailed history should be taken to evaluate other bone scan. systemic illness that can affect treatment or increase side effects. An ideal patient is one who has multiple painful FOLLOW-UP bone metastases positive on bone scan and who is clinically Patients are usually seen by their medical oncologist in experiencing worsening of pain while on nonnarcotic anal- follow-up. Blood counts are obtained at least weekly for the gesics. A bone scan is necessary to document metastatic first 6 wk and more frequently if there is evidence of 153 disease at the site of pain. With Sm, images can be toxicity. A drop in counts may be seen by 2Ð4 wk after obtained after the dose is administered, making it possible to treatment. Blood counts, notably thrombocyte and neutro- confirm uptake at the metastatic sites. The imaging is done phil counts, should be obtained until all counts are normal; the same day (2Ð4 h) or the next day (the latter has the return to pretreatment baseline may not always occur. Pa- advantage of better visualization of lumbosacral and pelvic tients whose blood counts do return to pretreatment values disease, as there is clearance from the urinary system). may be retreated, generally not before 3 mo. In summary, bone pain palliation therapy with radiophar- ADMINISTRATION OF RADIOPHARMACEUTICAL maceuticals is a cost-effective systemic therapy to relieve AGENT pain from skeletal metastases with a consequent decrease in Once eligibility is established, the patient is treated in an morbidity with an improvement in quality of life; use of outpatient setting. A worksheet for assessing the eligibility bone-seeking radiopharmaceuticals, by themselves or as may be used (Fig. 3). The patient is instructed about the part of a multimodality regimen, may also reduce disease radiation safety precautions. Informed consent is obtained. progression. It should be actively considered especially in Patient identifiers are checked. An intravenous line is in- patients with widespread metastasis. The ability to use this serted and one must ensure good blood return and free flow treatment with other therapies with added benefitisdefi- of the saline flush to prevent extravasation of tracer. When nitely an asset. Although single therapy has been shown to

TABLE 3 Checklist Before Administration of Radiopharmaceutical

General Laboratory

Positive bone scan (within 8 wk): abnormal uptake corresponding to pain sites Hemoglobin Ͼ 90 g ⅐ LϪ1 Estimated life expectancy Ͼ 3 mo (especially for agents with longer half-life) Total white cell count Ͼ 3.5 ϫ 109 LϪ1 Refractory bone pain despite analgesics Absolute neutrophil count Ͼ 1.5 ϫ 109 LϪ1 Treatment of refractory bone pain despite analgesics Platelets Ͼ 60 ϫ 109 LϪ1 No chemotherapy, external beam radiation, or treatment with bisphosphonates during Urea Ͻ 12 mmol ⅐ LϪ1 6 wk before therapy with agent (especially for 153Sm)

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