Predictors Of Response

It is difficult to determine what patient characteristics, other than the presence of a pathologic fracture, indicate a poor chance of responding to treatment of bone pain with radiopharmaceuticals. Cytopenias and a decrease in tumor markers caused by these radiopharmaceuticals do not correlate well with response. The presence of narcotic tolerance does not indicate the likelihood of response. Higher dosages than those which have been empirically determined to be effective do not yield greater response rates.

Recent studies have again suggested that a larger tumor burden may indicate a lower chance for successful outcome, perhaps because there are fewer radioactive molecules then to be distributed over a relatively larger bone tumor mass. A related Chinese study noted a statistically significant relationship between bone uptake of radiopharmaceutical (Sm-153 lexidronam) and therapeutic effect, again suggesting that dosimetric considerations may improve patient selection and the amount of activity injected.

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