Thyrogen (thyrotropin alfa for injection) is indicated for use as an adjunctive diagnostic tool for serum thyroglobulin (Tg) testing with or without radioiodine imaging in the follow-up of patients with well-differentiated thyroid cancer.

Thyrogen (thyrotropin alfa for injection) is indicated for use as an adjunctive treatment for radioiodine ablation of thyroid tissue remnants in patients who have undergone a neartotal or total thyroidectomy for well-differentiated thyroid cancer and who do not have evidence of metastatic thyroid cancer.

Potential Clinical Uses

1. Thyrogen Tg testing may be used in patients with an undetectable Tg on thyroid hormone suppressive therapy to exclude the diagnosis of residual or recurrent thyroid cancer (see CLINICAL PHARMACOLOGY, Clinical Trials, Thyroglobulin (Tg) Results).
2. Thyrogen treatment may be used in combination with radioiodine (¹³¹I) to ablate thyroid remnants following near-total thyroidectomy in patients without evidence of metastatic disease.
3. Thyrogen testing may be used in patients requiring serum Tg testing and radioiodine imaging who are unwilling to undergo thyroid hormone withdrawal testing and whose treating physician believes that use of a less sensitive test is justified.
4. Thyrogen treatment and testing may be used in patients who are either unable to mount an adequate endogenous TSH response to thyroid hormone withdrawal or in whom withdrawal is medically contraindicated.

Considerations in the Use of Thyrogen

1. Even when Thyrogen-stimulated Tg testing is performed in combination with radioiodine imaging, there remains a meaningful risk of missing a diagnosis of thyroid cancer or of underestimating the extent of disease. Therefore, thyroid hormone withdrawal Tg testing with radioiodine imaging remains the standard diagnostic modality to assess the presence, location and extent of thyroid cancer.
2. Although Thyrogen appeared noninferior to thyroid hormone withholding in a study of postsurgical thyroid remnant ablation, long-term clinical outcome data are limited. Due to the relatively small clinical experience with Thyrogen in remnant ablation, it is not possible to conclude whether long-term thyroid cancer outcomes would be equivalent after use of Thyrogen or use of thyroid hormone withholding for TSH elevation prior to remnant ablation.
3. Clinicians employ a wide range of 131I activities to achieve remnant ablation in patients who have been prepared by withholding of thyroid hormone. The primary study of Thyrogen for remnant ablation employed 100 mCi ± 10% in all patients. Data are inadequate to determine if a lower dose of radioiodine would be effective when Thyrogen is used as an adjunct to radioiodine in postsurgical thyroid remnant ablation.
4. Thyrogen Tg levels are generally lower than, and do not correlate with Tg levels after thyroid hormone withdrawal (see CLINICAL PHARMACOLOGY, Thyroglobulin (Tg) Results).
5. A newly detectable Tg level or a Tg level rising over time after Thyrogen, or a high index of suspicion of metastatic disease, even in the setting of a negative or low-stage Thyrogen radioiodine scan, should prompt further evaluation such as thyroid hormone withdrawal to definitively establish the location and extent of thyroid cancer. On the other hand, none of the 31 patients studied with undetectable Thyrogen Tg levels ( < 2.5 ng/mL) had metastatic disease. Therefore, an undetectable Thyrogen Tg level suggests the absence of clinically significant disease (see CLINICAL PHARMACOLOGY, Clinical Trials).
6. The decisions whether to perform a Thyrogen radioiodine scan in conjunction with a Thyrogen serum Tg test and whether and when to withdraw a patient from thyroid hormone are complex. Pertinent factors in these decisions include the sensitivity of the Tg assay used, the Thyrogen Tg level obtained, and the index of suspicion of recurrent or persistent local or metastatic disease. In the clinical trials, combination Tg and scan testing did enhance the diagnostic accuracy of Thyrogen in some cases (see CLINICAL PHARMACOLOGY, Clinical Trials).
7. The signs and symptoms of hypothyroidism which accompany thyroid hormone withdrawal are avoided with Thyrogen (see CLINICAL PHARMACOLOGY, Clinical Trials, Quality of Life, Hypothyroid Signs and Symptoms).

A two-injection regimen is recommended for Thyrogen administration.

The two-injection regimen is Thyrogen 0.9 mg intramuscularly (IM), followed by a second 0.9 mg IM injection 24 hours later.

After reconstitution with 1.2 mL Sterile Water for Injection, a 1.0 mL solution (0.9 mg thyrotropin alfa) is administered by intramuscular injection to the buttock.

For radioiodine imaging or remnant ablation, radioiodine administration should be given 24 hours following the final Thyrogen injection. Diagnostic scanning should be performed 48 hours after radioiodine administration, whereas post-therapy scanning may be delayed additional days to allow background activity to decline.

The following parameters utilized in the second Phase 3 study are recommended for diagnostic radioiodine scanning with Thyrogen:

• A diagnostic activity of 4 mCi (148 MBq) ¹³¹I should be used.
• Whole body images should be acquired for a minimum of 30 minutes and/or should contain a minimum of 140,000 counts.
• Scanning times for single (spot) images of body regions should be 10-15 minutes or less if the minimum number of counts is reached sooner (i.e. 60,000 for a large field of view camera, 35,000 counts for a small field of view).

For radioiodine ablation of thyroid tissue remnants, the activity of ¹³¹I is carefully selected at the discretion of the nuclear medicine physician. Studies with Thyrogen were conducted using 100 mCi ± 10% of ¹³¹I. Data are inadequate to determine if a lower dose of radioiodine would be effective when Thyrogen is used as an adjunct to radioiodine in postsurgical thyroid remnant ablation.

For serum Tg testing, the serum sample should be obtained 72 hours after the final injection of Thyrogen.

Instructions For Use

Thyrogen (thyrotropin alfa for injection) is for intramuscular injection to the buttock. The powder should be reconstituted immediately prior to use with 1.2 mL of Sterile Water for Injection, USP. Each vial of Thyrogen and each vial of diluent, if provided, is intended for single use. Discard unused portion of the diluent.

Thyrogen should be stored at 2-8°C (36-46°F). Each vial, after reconstitution with 1.2 mL of the accompanying Sterile Water for Injection, USP, should be inspected visually for particulate matter or discoloration before use. Any vials exhibiting particulate matter or discoloration should not be used. If necessary, the reconstituted solution can be stored for up to 24 hours at a temperature between 2°C and 8°C, while avoiding microbial contamination.

DO NOT USE Thyrogen after the expiration date on the vial. Protect from light.

Thyrogen (thyrotropin alfa for injection) is supplied as a sterile, non-pyrogenic, lyophilized product. It is available either in a two-vial or a four-vial kit. The two-vial kit contains two 1.1 mg vials of Thyrogen (thyrotropin alfa for injection). The four-vial kit contains two 1.1 mg vials of Thyrogen, as well as two 10 mL vials of Sterile Water for Injection, USP.

NDC 58468-1849-4 (4-vial kit)
NDC 58468-0030-2 (2-vial kit)

Store at 2-8°C.

Thyrogen® (thyrotropin alfa for injection)

Genzyme Corporation, 500 Kendall Street, Cambridge, MA 02142. (800) 745-4447. FDA Rev date: 8/12/2008

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