Levothyroxine suppression of thyroglobulin in patients with differentiated thyroid carcinoma

Levothyroxine-induced serum free thyroxine response following radioactive iodine administration in patients thyroidectomized for differentiated thyroid cancer: A randomized controlled trial

PURPOSE

Patients undergoing thyroidectomy for differentiated thyroid cancer (DTC) may require 131-radioactive iodine (RAI) administration for remnant ablation or disease treatment. After ingestion, RAI resides within the gastrointestinal tract potentially leading to mucosal damage and abnormalities in the absorption of levothyroxine (LT4). The aim of this study was to evaluate whether serum FT4 peak, induced by a LT4 challenge, changes according to the LT4 formulation (solid or liquid) in both RAI and non-RAI-treated DTC patients.

METHODS

This was a monocentric controlled clinical trial, with a parallel two-groups (1:1) randomization of sequence of LT4 formulation. Patients received 200 mcg LT4 orally administered at 08:00 h, in both solid and liquid formulation, at one-week interval, at baseline and after 1, 3, and 6 months from RAI administration. At each time-point, circulating FT4 was evaluated both before LT4 assumption as well as after 1 and 3 h. FT4 increments were evaluated as area under the curve response (AUC). Analogous protocol with the same time-intervals was followed for non-RAI patients.

RESULTS

The trial included 29 consecutive DTC patients, nineteen of whom were submitted to RAI. In RAI subjects, we observed an overall significant reduction in serum FT4 increments with the most relevant decrease at the 1-month time-point, (FT4 AUC: 4.46 ± 0.72 (M ± SD) vs 4.07 ± 0.63 in baseline vs 1-month, P = 0.001) without any difference between the two LT4 formulations. No difference in serum FT4 AUC was found in non-RAI subjects.

CONCLUSION

LT4-induced serum FT4 responses are reduced following RAI administration in thyroidectomized DTC patients.

Thyrotropin suppression increases the risk of osteoporosis without decreasing recurrence in ATA low- and intermediate-risk patients with differentiated thyroid carcinoma

BACKGROUND

Levothyroxine suppression of thyrotropin (TSH) is broadly applied to patients with thyroid cancer despite lack of consensus on the optimal TSH concentration necessary to reduce cancer recurrence while minimizing toxicity from subclinical hyperthyroidism. The objectives of this study were to examine the beneficial effects and the cardiac and skeletal toxicity of TSH suppression in well-differentiated thyroid carcinoma (DTC).

METHODS

A total of 771 patients (569 women) at ATA low or intermediate risk of recurrence, with a mean age of 48±14 years, and undergoing total thyroidectomy at a tertiary care center between 2000 and 2006 were followed for a median of six and a half years. They were divided into a suppressed TSH group (median TSH ≤0.4 mIU/L) and a nonsuppressed group (median TSH >0.4 mIU/L). Structural recurrence of thyroid cancer, postoperative atrial fibrillation (AF), and osteoporosis were examined in the two groups. Osteoporosis was only examined in women.

RESULTS

A total of 43/771 (5.6%) patients recurred, 29/739 (3.9%) patients were diagnosed with postoperative osteoporosis, and 17/756 (2.3 %) were diagnosed with postoperative AF. Despite similar rates of recurrence (HR 1.02, p=0.956 [CI 0.54-1.91]), patients treated to a median TSH ≤0.4 mIU/L were at increased postoperative risk of a composite outcome of AF and osteoporosis (HR 2.1, p=0.05 [CI 1.001-4.3]) compared to those not suppressed. A differential risk of AF alone (HR 0.78, p=0.63 [CI 0.3-2.1]) was not detected, but postoperative osteoporosis was increased among women with a suppressed TSH compared to those not suppressed (HR 3.5, p=0.023 [CI 1.2-10.2]). The increased risk of postoperative osteoporosis disappeared when the patient's median TSH was maintained around 1 mIU/L.

CONCLUSION

TSH suppression significantly increases the risk of postoperative osteoporosis without changing tumor recurrence in ATA low- and intermediate-risk patients with DTC. Future interventions should focus on avoiding harm in indolent disease.

Current recommendations for levothyroxine treatment of differentiated thyroid cancer patients are not properly implemented in clinical practice

BACKGROUND

Levothyroxine (L-T4) treatment aims to minimize the risk of differentiated thyroid cancer (DTC) recurrence and should be tailored to patient risk stratification and potential morbidity from adverse effects.

AIM

To evaluate the effectiveness of current recommendations on L-T4 treatment of DTC patients in clinical practice.

MATERIAL AND METHODS

We submitted to in-person interviews and revised the charts of 139 low-risk (LR) and 57 not-low-risk (NLR) DTC patients. A second evaluation made 24-60 months after surgery reclassified 131 patients who maintained (thyroglobulin) Tg≤2 ng/dl with no evidence of relapse/recurrence as LR, whereas the remaining 65 cases were considered NLR.

RESULTS

Only 27% LR patients were appropriately controlled; 18% were kept suppressed; 49% maintained serum TSH levels between 0.11-0.4 mU/l; 21% had TSH=2.5- 4.5 mU/l; and 12% TSH>4.5 mU/l. Among the NLR patients, 24 (37%) of the patients presented serum TSH levels above goal, including 13 (20%) patients with TSH>4.5 mU/l. There were 4 NLR elders whose TSH levels were kept between 0.41 and 4.5 for medical reasons; likewise, 28 NLR patients maintained with low but not undetectable serum TSH levels had cardiovascular and/or bone risk factors, but all the remaining 24 NLR patients were not adequately controlled because of poor treatment compliance. On the other hand, 45% of 152 inappropriately controlled patients presented risks for bone fractures, including 33 patients kept with low serum TSH levels without medical indication.

CONCLUSION

We concluded that guidelines are not adequately applied and alternative strategies aiming to increase adherence are urgently needed for DTC patients.

Management of thyroid cancers

Thyroid cancers cover a large spectrum of disease with diametrically opposite prognosis. At one end of the spectrum we have the well differentiated cancers which carry an excellent prognosis, while at the other end there is anaplastic cancer with high mortality rates and dismal prognosis. Management of thyroid cancers still has some controversial issues due to lack of randomized controlled trials. Extent of surgery, extent of neck dissection, role of radioiodine treatment and thyroid stimulating hormone suppression are still debatable. In this review, we highlight these controversial issues and give guidelines for the management and follow up of patients with thyroid cancer.

Papillary thyroid cancer: medical management and follow-up

The incidence of epithelial derived thyroid cancer (papillary thyroid cancer and follicular thyroid cancer, known collectively as differentiated thyroid cancer) is rising. About 80% of patients with thyroid cancer have PTC and are best treated with thyroidectomy and functional lymph node dissection, followed by radioiodine ablation or therapy and performance of a posttreatment whole-body scan, followed by thyroid stimulating hormone (TSH) suppression. One year after radioiodine administration, the use of sensitive thyroglobulin (Tg) assays can separate the vast majority of patients with persistent disease from those who are free of disease and unlikely to have recurrent disease all without the need for repeat whole-body radioiodine imaging. Patients with detectable serum Tg during TSH suppression (Tg-on) or Tg that rises above 2 ng/mL after TSH stimulation (TSH-Tg) are highly likely to harbor residual tumor. TSH stimulation can be achieved using either thyroid hormone withdrawal or recombinant human TSH (rhTSH). Highly skilled screening neck ultrasonography can identify a few additional patients with subcentimeter residual neck lymph node metastases not detected by TSH-Tg. However, ultrasonography and chest computed tomography (CT) are most critical for tumor localization in those patients with Tg values that suggest residual disease or in those patients with persistent antithyroglobulin antibodies (TgAb) that falsely lower Tg measurement. TgAb quantitative titers typically resolve steadily over just a few years in patients free of disease after initial therapy. Another paradigm shift is the recognition that most patients who eventually achieve freedom from disease do so by surgery with fewer patients cured by repetitive radioiodine treatments, and even fewer cured with external beam radiation. Patients who appear to be free of disease require a lifetime of follow-up to optimize levothyroxine treatment, and they will undergo periodic stimulation testing because some will still manifest recurrent disease. Patients with persistent disease despite negative ultrasonography, chest CT, and whole-body radioiodine imaging may have a tumor identified by fluorodeoxyglucose positron emission tomography, optimally performed with combined TSH stimulation and image fusion with CT or magnetic resonance imaging. Patients with metastatic disease who are unresponsive to conventional treatment are encouraged to participate in increasingly available thyroid cancer-specific clinical trials using targeted experimental oral or intravenous chemotherapeutic agents to address this tumor that has historically proven resistant to conventional chemotherapeutic agents.

Three-week thyroxine withdrawal thyroglobulin stimulation screening test to detect low-risk residual/recurrent well-differentiated thyroid carcinoma

Measurement of serum TSH-stimulated thyroglobulin (Tg) is recognized as a sensitive method for detecting residual/recurrent well-differentiated thyroid carcinoma (WDTC) in patients previously treated by surgery and radioactive iodine (RAI) ablation therapy. WDTC patients who have an undetectable serum Tg on thyroid hormone therapy (THT) in the absence of Tg-antibody interference are considered to be at low risk for residual/recurrent disease. Traditional management has been to withdraw T4 for 4-6 weeks or T3 for 2 weeks to stimulate endogenous TSH. However, this prolonged THT withdrawal induces hypothyroidism and its concomitant morbidity. In the present study, we assess the efficacy of shortening the time of T4 withdrawal to only 3 weeks for detecting residual/recurrent WDTC as a sufficient serum TSH stimulus for obtaining a positive serum Tg result without a routine diagnostic whole body scan (WBS). Additionally, we have evaluated the impact of such a T4 withdrawal interval on quality of life and loss of employment time. A total of 181 patients with WDTC selected for study had previously been treated with a bilateral surgical thyroidectomy followed by RAI ablation therapy (average post-surgery to follow-up interval of 10.8 yr). All of the cohort had an undetectable (< 1 microg/l) serum Tg on THT without Tg-antibody interference. Serum TSH and Tg were measured before and after cessation of T4 therapy for 3 weeks. A serum Tg > or = 2 microg/l was considered positive for residual/recurrent disease. A quality of life questionnaire [Short-Form 36 (SF-36)] was administered before withdrawal, at peak TSH and after resumption of therapy. From the completed SF-36 questionnaires, the overall degree of functional impairment was not severe and did not result in loss of employment time. Moreover, this protocol identified three possible responses to the 3-week T4 withdrawal interval as follows: a) serum Tg undetectable with TSH > or = 25 mIU/l (approximately 75% of total cohort); b) serum Tg > or = 2 microg/l (approximately 10% of total cohort) which will require further investigation and treatment for residual/recurrent disease; c) undetectable serum Tg with inadequate TSH rise (approximately 15% of total cohort), which will require TSH stimulation by either longer T4 withdrawal or recombinant human TSH to exclude residual disease. We conclude that a stimulated serum Tg test performed 3 weeks after T4 withdrawal is a simple and cost-effective first-line screening test with minimal morbidity which is sufficient to evaluate low-risk WDTC patients for recurrent/residual carcinoma.