Radiopharmaceutical Therapy

Particle-emitting bone-seeking radiopharmaceuticals have attracted the attention of the nuclear medicine community over the last three decades for the treatment of the pain of osteoblastic metastases. For the eight pharmaceuticals appearing in Table 1 there are published data on clinical trials in humans. All are reactor produced, and all emit a beta particle except for tin (Sn)-117 pentetate and strontium-85 (Sr-85) which produce low energy conversion electrons. Sr-85 also yields low energy X-rays. The radiopharmaceutcials in Table 1 are listed in descending order by the progressively longer half-lives of the radionuclide involved. The maximum and mean energy of the emitted particle, with the corresponding maximum and mean particle ranges in millimeters, and the energy of any emitted gamma photons, are also tabulated. Of these eight, only phosphorus-32 (P-32) as sodium phosphate, Sm-153 lexidronam (EDTMP), and Sr-89 chloride are commercially available in the United States, although rhenium-186 (Re-186) etidronate (HEDP) is widely employed in Europe.

Table 1 Beta or Electron-Emitting Radiopharmaceuticals for Painful Metastases

Gamma

Max

Mean

MeV

Radiopharma

tl/2

Maximum

Mean

range

range

(% abundance)

ceutical

(d.)

Eb (MeV)

Eb (MeV)

(mm)

(mm)

half-life

188Re(Sn)HEDP

0.7

2.12

0.73

11.0

2.7

0.155 (10%)

0.79

3.1

153Sm-EDTMP

1.9

0.81

0.23

2.5

0.6

0.103 (28%)

90Y-citrate

0.070 (5%)

2.7

2.27

0.94

11.1

2.5

186Re(Sn)HEDP

3.8

1.07

0.33

4.5

1.1

0.137 (9%)

117mSn-DTPA

13.6

0.127a

n.a.

0.27

0.2

0.159 (86%)

0.152a

n.a.

0.3

32P-phosphate

14.3

1.71

0.70

7.9

3.0

89Sr-chloride

50.5

1.46

0.58

7.0

2.4

0.909 (0.10%)

85Sr-chloride

64

0.025a

n.a.

10

0.514

0.040a

n.a.

plus 10-15 keV

x-rays

aConversion electrons Abbreviation: n.a., not available.

aConversion electrons Abbreviation: n.a., not available.

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