[131I-therapy of differentiated thyroid carcinoma with distant metastases--relation between absorbed dose by quantitative SPECT and outcome of the patients in thyroid carcinoma].

ABSTRACT

The correlation of absorbed doses of tumors in 18 patients of differentiated thyroid carcinoma with distant metastases, who were treated by 131I and followed over 5 years, with their outcome were analyzed and the clinical significance of determination of absorbed dose was discussed. Radioactivities of 131I in the tumors were measured by using SPECT at the time of therapy. Absorbed dose was calculated based on the MIRD equation. Outcome of 8 patients were evaluated as good and their absorbed dose was 10-630 Gy with 2-22 g of tumor volume, 1.2-3.5 days of effective half life (EHL) and follow-up term was 8.6 +/- 0.9 years. The absorbed dose of 10 patients whose outcome were evaluated as poor, was 5-81 Gy with 7-215 g of tumor volume, 1.3-5.3 days of EHL and follow-up term was 5.6 +/- 2.5 years. The initial treatment seemed to be important for 131I therapy, since the absorbed doses in the following therapy became reduced. When the absorbed dose of the tumor exceeded over 94 Gy at initial treatment, good clinical courses were obtained. These results indicate that the quantitative SPECT for 131I therapy is clinically valid and that the calculated absorbed doses correlate well with outcome of the patients.