99mTc-sestamibi radio-guided surgery of loco-regional 131Iodine-negative recurrent thyroid cancer

Abstract

Aim We report here our experience in a larger series of differentiated thyroid cancer (DTC) patients who had been treated by 99mTc-sestamibi radio-guided surgery (RGS) for 131Iodine ( 131I)-negative loco-regional recurrent disease. Methods Fifty-eight patients with loco-regional 131I-negative recurrent disease from DTC were studied with 99mTc-sestamibi directed RGS using a hand-held 11-mm gamma probe as an intra-operative detector. Patients were selected for RGS on the basis of (a) progressive increase of serum thyroglobulin (Tg) levels after first treatment during follow-up, (b) negative high dose (100 mCi, 3.7 GBq) 131I whole-body scan, and (c) positive pre-operative 99mTc-sestamibi scintigraphy for the presence of loco-regional recurrent disease. There were 41 papillary (1 “tall” cell variant), 13 follicular and 4 Hürthle cells tumours. In 14 patients thyroid cancer recurred in the thyroid bed while cervical lymph node metastases were found in 37 patients, and 7 patients had recurrent disease both in the thyroid bed and in cervical lymph nodes. Results At bilateral neck exploration, 147 metastastic foci ranging from 4 mm to 51 mm in largest diameter (mean tumour diameter = 17.3 ± 9.5 mm) were removed. Eighty-five of them (58%) had been pre-operatively identified at 99mTc-sestamibi scintigraphy. After RGS, serum Tg levels normalised in 43 of 58 patients (serum Tg < 2 ng/ml – they were considered disease-free), serum Tg remained slightly increased in 12 patients without evidence of metastatic disease at scintigraphic and radiologic imaging (serum Tg < 10 ng/mg – they were considered living with microscopic disease), while serum Tg significantly increased up to values > 900 ng/ml in 3 patients who developed lung metastases. The mean lesion to background 99mTc-sestamibi uptake ratios decreased in all 58 patients ( p < 0.0001). Post-surgical follow-up ranged 6–72 months (mean ± SD = 29.6 ± 13.5 months). The operating surgeon assessed RGS as very useful in 14 patients in whom metastatic foci were embedded in fibrotic tissues or located behind blood vessels, useful in 22 patients, moderately useful 17 patients and not useful in 5 patients. Conclusion Our data suggest that a 99mTc-sestamibi intra-operative gamma probe can be used to identify and guide resection of recurrent loco-regional tumour in DTC patients with 131I-negative loco-regional metastatic foci.