PT  - JOURNAL ARTICLE
AU  - James C. Sisson
AU  - Barry L. Shulkin
AU  - Susan Lawson
TI  - Increasing Efficacy and Safety of Treatments of Patients with Well-Differentiated Thyroid Carcinoma by Measuring Body Retentions of <sup>131</sup>I
DP  - 2003 Jun 01
TA  - Journal of Nuclear Medicine
PG  - 898--903
VI  - 44
IP  - 6
4099  - http://jnm.snmjournals.org/content/44/6/898.short
4100  - http://jnm.snmjournals.org/content/44/6/898.full
SO  - J Nucl Med2003 Jun 01; 44
AB  - There is no consensus on the amount of 131I for treatment of patients with well-differentiated thyroid carcinoma; usual amounts vary widely. Body retention of 131I has been shown to be a valuable index of radiation toxicity. If a broad range of body retentions occurs among patients, then high and low retentions will be a basis for modifying the usual prescriptions for 131I to ensure safety and increase efficacy. Methods: After withdrawal of thyroid hormone in 87 patients, the fractional retention of diagnostic 131I in each body was measured at 2 d by a scintillation probe. In 43 patients, the retention was measured 2 d after therapeutic 131I. Results: Diagnostic retention varied from 0.01 to 0.51, with a median of 0.15. These retentions did not correlate with any index of health, thyroid hormone, or carcinoma status. Seventeen patients, previously treated with 131I, exhibited a significantly lower mean retention. In 43 patients, retention of diagnostic 131I was highly correlated with retention of therapeutic 131I: diagnostic predicted therapeutic retention with a mean error of 0.04. In 10 patients receiving thyroxine, the mean retention of diagnostic 131I after recombinant human TSH (rhTSH) was strikingly lower, 0.06, with a range of 0.016–0.16. Conclusion: Body retentions of 131I are easily measured and vary considerably among patients. Because increased therapeutic 131I will impart greater irradiation of tumor, and body retention has been accepted as an index of toxicity from 131I, the use of body retention could enable prescriptions of therapeutic 131I that enable increased efficacy while ensuring safety. If tumor retention is not proportionally decreased with the body retention of 131I after rhTSH, then rhTSH may enable increased therapeutic efficacy.