Inclusion Criteria

Patients greater than or equal to 18 years of age, with well-differentiated, non-medullary
thyroid cancer, including papillary (including follicular-variant), follicular, and
Hurthle cell.

Patients who recently have undergone a total or near-total thyroidectomy and are scheduled
to undergo initial 131I diagnostic studies and ablation.

Patients must have evidence of residual thyroid tissue after thyroid surgery confirmed by
ultrasound or other imaging technique (e.g., a technetium [Tc 99] pertechnetate or
thallium scan).

Patients who have undergone thyroidectomy or other thyroid surgery at least 6 weeks prior
to enrollment.

All patients who have been sustained on maintenance THST for at least 4 weeks, but not
longer than 12 weeks after thyroidectomy.

All patients who have confirmed serum TSH levels less than or equal to 0.5 mU per liter
within 7 days prior to the first Thyrogen dose, and prior to randomization.

Female patients of childbearing age must have a negative serum human chorionic
gonadotropin (HCG) pregnancy test prior to entering the study and within 5 days of any
131I administration and must be following an approved method of contraception.

Patients who are committed to following the protocol requirements as evidenced by
providing written informed consent.

Patients for whom a 131I scan is currently contraindicated because withdrawal from THST is
not an option due to pituitary dysfunction or other compelling medical reasons are
excluded.

Patients should not have a concurrent major medical disorder (e.g., documented cardiac
disease, debilitating cardiopulmonary disease, advanced renal failure, advanced liver
disease or advanced pulmonary disease) who may be too ill to adequately comply with the
requirements of this study.

Patients with non-thyroidal conditions known to effect 131I uptake (e.g., congestive heart
failure, renal failure) are excluded.

Patients should not have undergone any intravenous water soluble radiographic contrast
administration within the previous 4 weeks.

Patients should not have received intrathecal or cholecystographic iodinated contrast
agent administration within 3 months prior to enrollment.

Patients should not be taking drugs that affect thyroid or renal function (e.g., renal
drugs, lithium, or corticosteroids).

Patients should not be participating in another investigational drug study or in such a
study within 30 days of their enrollment in this study.

No patients with a recent history of alcoholism or drug abuse, severe emotional behavioral
or psychiatric problems who, in the opinion of the investigator, would not be able to
comply with the requirements of this study.