Optimal Measurement of Thyroglobulin Measurement Following Thyroidectomy
| Status: | Recruiting |
|---|---|
| Conditions: | Cancer, Cancer, Thyroid Cancer |
| Therapuetic Areas: | Oncology |
| Healthy: | No |
| Age Range: | 19 - Any |
| Updated: | 4/21/2016 |
| Start Date: | January 2015 |
| End Date: | June 2016 |
| Contact: | Whitney Goldner, MD |
| Email: | wgoldner@unmc.edu |
| Phone: | 402-559-6876 |
The optimal timing to measure thyroglobulin(Tg) after thyroidectomy is unknown in patients
with thyroid cancer. The ATA and NCCN guidelines are not specific on optimal timing of Tg
levels in post-op state and suggest anywhere between 2-12 weeks.
Hypothesis - Post -op Tg nadirs at 6-8 weeks .
Primary Objective -Determine optimal timing of post thyroidectomy Tg nadir, so to determine
the most accurate time to check post operatively.
Secondary Outcome - Determine factors that will affect Tg levels post operatively.
All adults age 19 and above already planning to undergo near total /total thyroidectomy for
reasons unrelated to the study.
Measure Tg , Tg Ab and TSH pre-op, post op ---> 7-14 days, 4 wk, 6 wk, and 3 month in
patients with pathology confirmed benign disease.
Measure Tg , Tg Ab , TSH pre-op, post op ---> 7-14 days, 4 wk, 6 wk, 3 month, 6 month, and
12 month in patients with thyroid cancer.
with thyroid cancer. The ATA and NCCN guidelines are not specific on optimal timing of Tg
levels in post-op state and suggest anywhere between 2-12 weeks.
Hypothesis - Post -op Tg nadirs at 6-8 weeks .
Primary Objective -Determine optimal timing of post thyroidectomy Tg nadir, so to determine
the most accurate time to check post operatively.
Secondary Outcome - Determine factors that will affect Tg levels post operatively.
All adults age 19 and above already planning to undergo near total /total thyroidectomy for
reasons unrelated to the study.
Measure Tg , Tg Ab and TSH pre-op, post op ---> 7-14 days, 4 wk, 6 wk, and 3 month in
patients with pathology confirmed benign disease.
Measure Tg , Tg Ab , TSH pre-op, post op ---> 7-14 days, 4 wk, 6 wk, 3 month, 6 month, and
12 month in patients with thyroid cancer.
Thyroid cancer, the most common endocrine tumor, constitutes 3.8% of all cancers. 62,980 new
cases were estimated in the U.S. in 20141, an increasing trend from the 37,200 new cases in
20092. 90% of all thyroid cancers are differentiated thyroid carcinomas (DTC), which include
both papillary and follicular thyroid carcinoma3.
Management of DTC involves a total thyroidectomy, with possible central and lateral neck
dissection if there are clinical lymph node involvement, except for low-risk lesions that
are unifocal, intrathyroidal, node-negative and measuring less than 1 cm in size.
Radioactive iodine ablation of any remnant thyroid tissue may follow a total thyroidectomy
depending on the risk stratification of the patient3. As for any cancer, management of
thyroid cancer involves long-term surveillance for early detection of disease recurrence3.
According to the ATA guidelines, postoperative surveillance includes regular (every 6 to 12
months) clinical evaluation for tumor recurrence, evaluation with neck ultrasound and serum
Thyroglobulin (Tg) levels while on levothyroxine replacement3. Serum Tg has become a very
useful and well-acknowledged marker in patients with thyroid cancer post thyroidectomy for
disease persistence, metastasis or recurrence.
Thyroglobulin is a 660 kDa dimeric glycoprotein that is exclusively produced and stored by
thyroid follicular cells in benign conditions, but also by well-differentiated thyroid
cancer cells4. A total thyroidectomy for higher risk patients is thus not only is important
to provide definitive treatment and decrease risk of recurrence, but also allows for long
term follow-up with Tg levels.
One study has reported Tg is eliminated through the liver and its half-life following total
thyroidectomy has been reported to be about 65.2 hours. The Tg level was noted to decrease
to less than 5-10 ng/ml 25 days after thyroidectomy, or after 7 to 10 half-lives in 11
patient samples5. Detection of Tg following the total thyroidectomy during long-term
surveillance would therefore suggest persistent thyroid tissue.
Despite the determined half-life of Tg, in a retrospective study with 36 patients with
low-risk papillary thyroid carcinoma, the unstimulated Tg level fell to < 0.5 ng/ml after 6
months postoperatively in only 61%, and after 2 years postoperatively in 100% of the
patients6. No prospective studies have yet determined the nadir of the Tg level post
thyroidectomy. In our personal clinical experience, unstimulated serum Tg levels may be
found undetectable 6 to 12 weeks following a total thyroidectomy.
The sensitivity, specificity, positive predictive value and negative predictive value of
unstimulated (normal or low TSH ) serum Tg in assessing completeness of thyroidectomy (< 0.5
ng/ml) have been reported to be 70%, 100%, 100% and 92% respectively6. Obtaining a basal
unstimulated serum Tg level post thyroidectomy not only determines the completeness of the
total thyroidectomy7, but also provides a basal level for future comparison during long-term
surveillance. The high negative predictive value allows for the identification of patients
less likely to have disease recurrence and provide less aggressive and more cost effective
management strategies3.
The optimal time to obtain an unstimulated serum Tg level has not yet been determined.
Obtaining the Tg level too early following the total thyroidectomy may result in a
misleadingly significant Tg level and erroneously suggest residual disease, thereby leading
to unnecessary further investigation and more aggressive management strategies. NCCN
guidelines suggest to check anywhere between 2-12 weeks in patients with thyroid cancer 8
Radioactive iodine ablation of remnant thyroid tissue may potentially be avoided with a
postsurgical stimulated Tg level of < 1ng/ml in low risk, well-differentiated thyroid
cancer9. This practice is not yet approved by the American Thyroid Association, and is less
likely to be feasible with no concensus on the timing of the Tg measurement.
The objective of this study is therefore to find the nadir of the unstimulated serum Tg
level following total thyroidectomy, and therefore the optimal time for Tg measurement in
postoperative surveillance.
cases were estimated in the U.S. in 20141, an increasing trend from the 37,200 new cases in
20092. 90% of all thyroid cancers are differentiated thyroid carcinomas (DTC), which include
both papillary and follicular thyroid carcinoma3.
Management of DTC involves a total thyroidectomy, with possible central and lateral neck
dissection if there are clinical lymph node involvement, except for low-risk lesions that
are unifocal, intrathyroidal, node-negative and measuring less than 1 cm in size.
Radioactive iodine ablation of any remnant thyroid tissue may follow a total thyroidectomy
depending on the risk stratification of the patient3. As for any cancer, management of
thyroid cancer involves long-term surveillance for early detection of disease recurrence3.
According to the ATA guidelines, postoperative surveillance includes regular (every 6 to 12
months) clinical evaluation for tumor recurrence, evaluation with neck ultrasound and serum
Thyroglobulin (Tg) levels while on levothyroxine replacement3. Serum Tg has become a very
useful and well-acknowledged marker in patients with thyroid cancer post thyroidectomy for
disease persistence, metastasis or recurrence.
Thyroglobulin is a 660 kDa dimeric glycoprotein that is exclusively produced and stored by
thyroid follicular cells in benign conditions, but also by well-differentiated thyroid
cancer cells4. A total thyroidectomy for higher risk patients is thus not only is important
to provide definitive treatment and decrease risk of recurrence, but also allows for long
term follow-up with Tg levels.
One study has reported Tg is eliminated through the liver and its half-life following total
thyroidectomy has been reported to be about 65.2 hours. The Tg level was noted to decrease
to less than 5-10 ng/ml 25 days after thyroidectomy, or after 7 to 10 half-lives in 11
patient samples5. Detection of Tg following the total thyroidectomy during long-term
surveillance would therefore suggest persistent thyroid tissue.
Despite the determined half-life of Tg, in a retrospective study with 36 patients with
low-risk papillary thyroid carcinoma, the unstimulated Tg level fell to < 0.5 ng/ml after 6
months postoperatively in only 61%, and after 2 years postoperatively in 100% of the
patients6. No prospective studies have yet determined the nadir of the Tg level post
thyroidectomy. In our personal clinical experience, unstimulated serum Tg levels may be
found undetectable 6 to 12 weeks following a total thyroidectomy.
The sensitivity, specificity, positive predictive value and negative predictive value of
unstimulated (normal or low TSH ) serum Tg in assessing completeness of thyroidectomy (< 0.5
ng/ml) have been reported to be 70%, 100%, 100% and 92% respectively6. Obtaining a basal
unstimulated serum Tg level post thyroidectomy not only determines the completeness of the
total thyroidectomy7, but also provides a basal level for future comparison during long-term
surveillance. The high negative predictive value allows for the identification of patients
less likely to have disease recurrence and provide less aggressive and more cost effective
management strategies3.
The optimal time to obtain an unstimulated serum Tg level has not yet been determined.
Obtaining the Tg level too early following the total thyroidectomy may result in a
misleadingly significant Tg level and erroneously suggest residual disease, thereby leading
to unnecessary further investigation and more aggressive management strategies. NCCN
guidelines suggest to check anywhere between 2-12 weeks in patients with thyroid cancer 8
Radioactive iodine ablation of remnant thyroid tissue may potentially be avoided with a
postsurgical stimulated Tg level of < 1ng/ml in low risk, well-differentiated thyroid
cancer9. This practice is not yet approved by the American Thyroid Association, and is less
likely to be feasible with no concensus on the timing of the Tg measurement.
The objective of this study is therefore to find the nadir of the unstimulated serum Tg
level following total thyroidectomy, and therefore the optimal time for Tg measurement in
postoperative surveillance.
Inclusion Criteria:
1. All patients already planning to undergo total /near total thyroidectomy for reasons
unrelated to this study.
2. Age 19 or older
Exclusion Criteria:
1. Children < 19 years
2. Pregnancy
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