Radio-guided surgery for lymph node recurrences of differentiated thyroid cancer

Abstract

The objectives of this study were to assess the reliability of radio-iodine (131I) and a gamma probe for radio-guided surgery (RGS) to detect and then radically dissect lymph node recurrences (LNRs) in 10 patients with differentiated thyroid cancer (DTC). The major inclusion criterion was the presence of an iodine-positive LNR after previous total thyroidectomy and at least two ineffective 131I treatments. The protocol was designed as follows. Day 0: all patients were hospitalized and received 3.7 GBq of 131I in the hypothyroid condition. Day 3: presurgery whole-body scan with a therapeutic dose (TxWBS). Day 5: neck surgery using a gamma probe (Navigator GPS, AutoSuture, Italy), recording the absolute counts and the lesion/background (L/B) counts ratio. Day 7: post-surgery TxWBS performed using the remaining radioactivity. The presurgery TxWBS was positive in all patients, and the post-surgery TxWBS showed a negative pattern in 7 of 10 patients, suggesting the efficacy of the surgical procedure in most of the patients. After RGS the mean decrease in the absolute counts and the L/B counts ratio were 77.6% (52.7% minimum, 94.6% maximum) and 77.4% (52.3% minimum, 94.8% maximum), respectively. After operation the surgeon judged the procedure to be decisive in two patients, favorable in six, and irrelevant in two. The final histologic examination showed the presence of 78 lymph node metastases (mean of 8 per patient). There were 33 neoplastic lesions found by both TxWBS and gamma probe evaluations; 41 were shown only by gamma probe, and 4 were negative by both TxWBS and gamma probe evaluations. This protocol permitted us to look for neoplastic foci with high sensitivity and specificity, and we were able to remove lymph node metastases resistant to radioiodine therapy at a single session. The protocol also allowed detection of some additional tumoral foci in sclerotic areas or behind vascular structures that are difficult to identify and were not seen at the presurgery TxWBS evaluation. However, because of the possible false-negative results, complete excision must be undertaken in high risk patients with a local recurrence to eradicate the largest number of lymph nodes, independent of the counts measured by the gamma probe.