Sunday, May 8, 2011

Radioisotopes in Treatment of Osseous Metastases

PHOSPHORUS 32
Radiophosphorus-labeled phosphates were the first radionuclides used to treat bone metastases. Since then, many reports have been published about the use of 32P in patients with prostate and breast carcinoma. The currently available product, 32P orthophosphate, is economically priced compared with similar beta-emitting radionuclides used for this purpose, but it has fallen into disuse because of the widely held impression that current 32P approaches are too toxic.

STRONTIUM 89 CHLORIDE

Although 89Sr is, like 32P, a pure betaemitting radioisotope, it has several theoretical advantages as a treatment agent for bony metastases. Strontium is found in the same periodic table family as is calcium and is metabolized in a similar fashion, with significant concentrations found in the skeleton and small amounts elsewhere in the body.

SAMARIUM 153 LEXIDRONAM

The US Food and Drug Administration has recently approved samarium 153 lexidronam chelated to ethylenediamene-tetramethylenephosphonic acid (153Sm-EDTMP) for the relief of pain in patients with osteoblastic bone metastases. This radioisotope, like 32P and 89Sr, emits low-energy electrons. Unlike the other approved agents, however, 153Sm has a shorter half-life (less than 2 days) and gamma emission suitable for imaging and prospective dose estimation.


RHENIUM 186 AND RHENIUM 188

Rhenium 186 (Sn) hydroxyethylidene diphosphonate (186Re-HEDP) has characteristics similar to those of 153Sm-EDTMP, with a beta emission half-life of 90.64 hours and a gamma emission suitable for imaging.

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