Background and purpose: Neck lymph node metastasis

most of which presents in central neck compartment

is common in patients with papillary thyroid carcinoma (PTC). The objective of this study was to investigate the relationship between the number of dissected central neck lymph nodes and clinical outcome after radioactive iodine (RAI) ablation in pN1a PTC with no more than 5 lymph nodes involvement. Methods: A total of 167 PTC patients who had 1-5 proven metastatic lymph nodes according to postoperative pathological diagnosis were retrospectively analyzed

all of whom underwent total or near total thyroidectomy and central lymph node dissection. After a median follow-up period of 26 months

the clinical outcome of each patient was evaluated as excellent response (ER)

indeterminate response (IDR)

biochemical incomplete response (BIR)

or structural incomplete response (SIR) according to the new American Thyroid Association guidelines. The accumulative ER rate (ER

n

) was calculated in patients with different numbers of dissected lymph nodes (ER

n

was defined as the proportion of patients who achieved ER with the dissected lymph node number of ≤n). The relationship between the number of dissected central neck lymph nodes and ER

n

were investigated. Results: As the increase in the number of dissected central neck lymph nodes，there was also an overall increase in ER

n

especially when n rose from 1 to 10. The values of ER

1

ER

5

ER

10

and ER

30

were 25.0%

66.7%

74.7% and 79.1%

respectively. Besides

the proportion of patients who achieved ER was higher in those with 10 or more dissected lymph nodes than in those with less than 10 (85.7% vs 73.3%

P=0.05). In the multivariate logistic regression analysis

both the dissected central lymph node number of ≥10 (OR=2.720

95%CI: 1.052-7.033

P=0.039) and the level of preablation stimulated thyroglobulin (OR=0.955

95%CI: 0.926-0.984

P=0.003)

were shown to contribute independently to ER. Conclusion: As the increasing number of dissected central neck lymph nodes

the percentage of pN

1a

PTC patients that achieved ER after RAI ablation generally rises. In pN

1a

PTC patients with no more than 5 lymph nodes involvement

a central compartment dissection with 10 or more lymph nodes might help them achieve ER after RAI ablation.