Long-term predictive value of highly sensitive thyroglobulin measurement.

Area of Science:

• Endocrinology
• Oncology
• Nuclear Medicine

Background:

• Differentiated thyroid cancer (DTC) management relies on monitoring thyroglobulin (Tg) levels.
• Distinguishing between stimulated and nonstimulated Tg measurements, and the influence of anti-Tg-antibodies (TgAbs), is crucial for accurate prognosis.
• Highly sensitive Tg (hsTg) assays offer improved detection capabilities.

Purpose of the Study:

• To evaluate the predictive capability of nonstimulated hsTg levels for stimulated Tg measurements, diagnostic imaging, recurrence, and DTC-related mortality.
• To assess the prognostic value of hsTg in DTC patients, both with and without TgAbs.

Main Methods:

• Retrospective analysis of 461 DTC patients treated and followed from 2004 onwards.
• Inclusion of patients with at least one post-treatment Tg measurement at least 3 months after I-131 ablation.
• Stratification of patients based on the presence or absence of TgAbs.

Main Results:

• In TgAb-negative patients, an unstimulated hsTg < 0.1 ng/ml had a 97.6% negative predictive value for a stimulated Tg ≥ 1.0 ng/ml.
• An unstimulated hsTg ≥ 0.1 ng/ml showed high sensitivity (90.0%) and specificity (94.1%) for detecting stimulated Tg ≥ 1.0 ng/ml.
• While unstimulated Tg ≥ 0.1 ng/ml did not significantly predict DTC-related death, higher levels (≥ 1.0 ng/ml) and stimulated Tg ≥ 1.0 ng/ml did, though this significance was lost when excluding patients with distant metastases.

Conclusions:

• Undetectable nonstimulated hsTg measurements indicate a very good prognosis in both TgAb-negative and TgAb-positive DTC patients, excluding those with distant metastases.
• The high negative predictive value of unstimulated hsTg testing supports its use in potentially obviating further diagnostic investigations.