Radioactive iodine administered for thyroid remnant ablation following recombinant human thyroid stimulating hormone preparation also has an important adjuvant therapy function.
BACKGROUND
In December 2007, the USFDA approved recombinant human thyroid stimulating hormone (rhTSH) for radioiodine remnant ablation after total thyroidectomy in patients with well-differentiated thyroid cancer without evidence of metastatic disease. Because previously undetected radioactive iodine (RAI)-avid metastatic lesions can be identified during remnant ablation, we sought to determine if rhTSH-stimulated uptake of RAI into these incidentally discovered metastases is associated with a significant therapeutic (tumoricidal) effect.


METHODS
This retrospective review describes the clinical outcome of 84 well-differentiated thyroid cancer patients in whom RAI-avid lesions outside the thyroid bed were first identified at the time of RAI remnant ablation (64 rhTSH stimulated, 20 thyroid hormone withdrawal [THW]) on either the diagnostic (63/84, 75%) or posttherapy (21/84, 25%) whole body scan (76 with locoregional metastasis only and 8 with pulmonary uptake). Following ablation, patients were classified as having either no evidence of disease or persistent disease on the basis of subsequent diagnostic whole body RAI scans, stimulated thyroglobulin, and cross-sectional imaging studies.


RESULTS
Despite having RAI-avid metastatic disease identified outside the thyroid bed at the time of initial ablation, 70% (45/64) of rhTSH-assisted patients and 55% (11/20) of the THW group had no evidence of disease at a median of 2.7 years following the initial RAI ablation (p = 0.159). THW and rhTSH-stimulated RAI ablation had similar efficacy in eliminating RAI-avid locoregional metastases (42/60, 70% of rhTSH and 10/16, 63% of THW, p = 0.65) and pulmonary metastases (3/4, 75% of rhTSH and 1/4, 25% of THW, p = 0.41).


CONCLUSIONS
Preparation with either rhTSH or THW in this retrospective study appears to have similar therapeutic (tumoricidal) effects on small volume RAI-avid metastatic disease incidentally discovered at the time of ablation in both locoregional lymph nodes and pulmonary parenchyma.
Tuttle
R Michael
RM
Endocrinology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA. tuttlem@mskcc.org
Lopez
Norma
N
Leboeuf
Rebecca
R
Minkowitz
Shaye M
SM
Grewal
Ravinder
R
Brokhin
Matvey
M
Omry
Gal
G
Larson
Steve
S
D055011:Ablation Techniques; D018263:Adenocarcinoma, Follicular / Q000628:therapy*; D000231:Adenocarcinoma, Papillary / Q000628:therapy*; D000328:Adult; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D011994:Recombinant Proteins / Q000627:therapeutic use*; D012189:Retrospective Studies; D013964:Thyroid Neoplasms / Q000628:therapy*; D013965:Thyroidectomy; D013972:Thyrotropin / Q000627:therapeutic use*; D016896:Treatment Outcome; D051598:Whole Body Imaging
D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D013972:Thyrotropin