Evaluation of the surgical completeness after total thyroidectomy for differentiated thyroid carcinoma

Background To quantify the rate of patients without thyroid remnants, to identify predictive factors for the absence of residual thyroid tissue and to evaluate number, site, size and function of thyroid remnants after total thyroidectomy for differentiated thyroid carcinoma (DTC). Methods Thousand one hundred and seventy-eight patients who underwent total thyroidectomy for DTC were evaluated; 343 patients with lymph node or distant metastases and 115 patients with detectable thyroglobulin autoantibodies (TgAb) were excluded. 131I ablative treatment (RAI) without preliminary diagnostic 131I whole body scans (DxWBS), and 24-h 131I quantitative neck uptake (RAIU test) and thyroglobulin (Tg) off L-T4 evaluation were performed in the remaining 720 pts. In 252 patients a 99mTc-pertecnetate pre-operative thyroid scan (99mTc-scan) was used for comparison with 131I neck scans after RAI to evaluate site of thyroid remnants. Only patients with thyroid remnants were evaluated for successful ablation 6–10 months after RAI. Results Post-treatment whole body scan (TxWBS) demonstrated lack of thyroid remnants in 50/720 patients and the best predictive factors for the absence of residual thyroid tissue were RAIU <1% and undetectable Tg off L-T4. Thyroid remnants were present in 670/720 patients. In 252 patients with 99mTc-scan, 617 sites of functioning thyroid tissue were found: 381 within and 236 outside the thyroid bed. Complete successful ablation was achieved in 610/670 patients with thyroid remnants. Conclusions This study confirms that most patients (93.1%) have thyroid remnant after total thyroidectomy for DTC. Most thyroid remnants were contralateral to tumour site and were even observed outside thyroid bed. However, a real total thyroidectomy, demonstrated by negative TxWBS, RAIU <1% and undetectable Tg off L-T4, was achieved in 6.9% of patients.