Maximal safe dose of I-131 after failure of standard fixed dose therapy in patients with differentiated thyroid carcinoma.
OBJECTIVE
The maximal safe dose (MSD) on the basis of bone marrow irradiation levels allows the delivery of a large amount of I-131 to thyroid cancer tissue. The efficacy of MSD therapy in differentiated metastatic thyroid cancers that persisted after conventional fixed dose therapy is investigated.


METHODS
Forty-seven differentiated thyroid carcinoma patients with non-responsive residual disease despite repetitive fixed dose I-131 therapy were enrolled in this study. Their postoperative pathologies were 43 papillary carcinomas and 4 follicular carcinomas. The MSD was calculated with the Memorial Sloan-Kettering Cancer Center protocol using serial blood samples. The MSDs were administered at intervals of 6 months. Treatment responses were evaluated using I-131 whole-body scans and serum thyroglobulin measurements.


RESULTS
The mean calculated MSD was 12.5 +/- 2.1 GBq (339.6 +/- 57.5 mCi). Of the 46 patients, 7 (14.9%) showed complete remission, 15 (31.9%) partial remission, 19 (40.4%) stable disease, and 6 (12.8%) disease progression. Of the patients who showed complete or partial remission, 15 (65%) showed response after the first MSD session and 6 (26%) showed response after the second session. Twenty-nine patients (62%) experienced transient cytopenia after therapy, but three did not recover to the baseline level.


CONCLUSIONS
The maximal safe dose provides an effective means of treatment in patients who failed to respond adequately to conventional fixed dose therapy. I-131 MSD therapy can be considered in patients who fail fixed dose therapy.
Lee
Jong Jin
JJ
Department of Nuclear Medicine, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul, 110-744, South Korea.
Chung
June-Key
JK
Kim
Sung Eun
SE
Kang
Won Jun
WJ
Park
Do Joon
DJ
Lee
Dong Soo
DS
Cho
Bo Youn
BY
Lee
Myung Chul
MC
D000328:Adult; D000368:Aged; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage* / Q000633:toxicity*; D007938:Leukemia / Q000139:chemically induced* / Q000517:prevention & control*; D008297:Male; D020714:Maximum Tolerated Dose; D008875:Middle Aged; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000633:toxicity; D011879:Radiotherapy Dosage; D013964:Thyroid Neoplasms / Q000532:radiotherapy*; D017211:Treatment Failure; D016896:Treatment Outcome; D055815:Young Adult
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals