Treatment effect of higher cumulativedose of 131I therapy for differentiated thyroid carcinoma with diffuse pulmonary metastases

1548 Objectives: To investigate treatment effect of higher cumulative dose of 131I therapy with three times for diffuse pulmonary metastases of differentiated thyroid carcinoma. Methods: To review the analysis of 77 cases of lung metastases with 131I therapy with three times between December 2012 and December 2018, with diffuse pulmonary metastases. The curative effect of 131I was evaluated by Tg, 131I-WBS(131I-whole body scan) and CT (computerized tomography) after 131I treatment. The curative effect was divided into four types: cure, improvement, stability and progress. The patients were divided into CT positive group (44 cases) and negative group (33 cases) according to whether there were pulmonary nodule on chest CT. According to the dose of 131I and CT positive patients were divided into the lower dose group (cumulative 131I dose≦450 mCi; The dose of 131I was 100mCi~150mCi, 150mCi, 150mCi with three times respectively) and the higher dose group (cumulative 131I dose≧500mCi; The dose of 131I was150mCi, 150mCi~250mCi, 200mCi~250mCi with three times respectively). The patients with negative CT were divided into the lower dose group (cumulative 131I dose 400 mCi; The dose of 131I was 100mCi, 150mCi, 100mCi~150mCi with three times respectively) and the higher dose group (cumulative 131I dose ≥ 450 mCi; The dose of 131I was100mCi~150mCi, 150mCi~200mCi, 150mCi~200mCi with three times respectively). Results: In 44 cases of CT positive group, 14 cases (58.3%) were improved and 10 cases (41.7%) were stable in the lower dose group respectively,12 cases (60%) were improved and 8 cases (40%) were stable in the higher dose group respectively. There was no significant difference between the two groups in the improvement and stabilization of the disease (x2=1.455,P=0.228>0.05). In 33 patients with negative CT, 6 cases (25%) were cured and 18 cases (75%) were improved in the lower dose group respectively,6 cases (66.7%) were cured and 3 cases (33. 3%) were improved in the higher dose group respectively. There was no significant difference between the two groups in the cure of the disease and the improvement of the disease (x2=2.455,P=0.117>0.05). Conclusions: For patients with diffuse lung metastasis of differentiated thyroid carcinoma, no matter whether the chest CT showed positive or negative metastatic lesions, the higher cumulative dose of 131I did not significantly improve the curative effect of metastatic foci. From the perspective of radiation dosimetry, conventional or lower dose 131 I is recommended for the treatment of lung metastases in differentiated thyroid carcinoma.Key words:Diffuse pulmonary metastases; 131I;computerized tomography