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Eleven retrospective studies comparing TT with TT 1 pCCND (either ipsilateral or bilateral) were selected and are summarized in Table 2-1. The incidence of oc- cult lymph node metastases among patients with pCCND ranged from 26% to 82% (mean, 49%). Overall, the incidence of locoregional recurrence ranged from 1.5% to 19% (mean, 6.2%) and 3.1% to 14% (mean, 4.7%) in the TT and TT 1 pCCND groups, respectively. However, the majority of the retrospective studies have relatively short ( , 5 years) follow-up. Of the large retrospective studies, the one with the longest mean follow-up (129 months) reported improved 10-year local control and disease- free survival for patients who underwent pCCND, noting significant improvement over TT alone. Overall, the proportion of patients receiving RAI therapy was higher in patients undergoing pCCND. Furthermore, the rates of temporary hypocalcemia were significantly higher in patients undergoing pCCND, whereas the rates of perma- nent hypoparathyroidism and RLN palsy were generally equal. 142 The locoregional recurrence rates reported by three meta-analyses, which evalu- ated the use of pCCND in clinically node-negative PTC, are included in Table 2-2. Two meta-analyses showed no statistically significant differences in the overall rate of lymph node recurrence when comparing TT 1 pCCND with TT alone in patients with PTC. In the study by Wang et al, 158 the authors found that the number of patients needed to treat with pCCND to prevent one locoregional recurrence was 31. The study by Lang et al 137 showed that patients who underwent TT with pCCND were more likely to have postoperative RAI ablation, temporary hypocalcemia, and a lower risk of locoregional recurrence than were those who had TT alone (35% reduction in risk of recurrence). 137 The authors cautioned that it was unclear how much of the risk reduction in recurrence is related to the increased use of RAI therapy and cited the potential selection bias in some of the studies examined. SUMMARY When pCCND is performed, metastatic lymph nodes are found in nearly 50% of patients with cN0 disease. With relatively short follow-up ( , 5 years), locoregional re- currence rates are similar in patients who do not undergo pCCND and those who do. Furthermore, when pCCND is performed in specialized centers, rates of permanent hypoparathyroidism and recurrent laryngeal nerve injury appear to be similar between groups. Because of the discovery of micrometastatic lymphadenopathy, pCCND leads to upstaging of PTC, and an increase in the use of RAI therapy when metastatic lymph nodes are identified is noticeable. Therefore, it may be reasonable to offer pCCND to patients with PTC if the information will change practice. Whether the added knowl- edge afforded by pCCND regarding the presence or absence of microscopic disease in the regional lymph nodes will lead to future modulations in the use of RAI therapy cannot be answered at this time. The use of RAI therapy appears to be universal when metastatic lymph nodes are found and appears to occur regardless of whether the lymph node metastases are occult and microscopic or not. Lack of consensus and multidisciplinary decision-making coupled with poor understanding regarding the biology of the disease contributes to the use (or abuse) of RAI in PTC. 149,167 With the publication of the most recent American Thyroid Association guidelines, 42 which