Subgrouping of N1a Stage Papillary Thyroid Carcinoma with Positive Node Ratio

Korean Journal of Head & Neck Oncology 2016;32(1):13-19.
Published online May 30, 2016.

Min Wan Lee;Jin Seong Cho;Dong Hoon Cho;Young Jae Ryu;Min Ho Park;Jung Han Yoon

갑상선유두상암의 중앙림프절 전이율에 따른 N1a병기의 세분화

이민완;조진성;조동훈;유영재;박민호;윤정한

Abstract

Background : The 2015 American thyroid association (ATA) guidelines greatly expanded section on risk strat-ification of thyroid cancer. Definition of "Low risk of recurrence" has expanded, by inclusion of small volume lymph node involvement, such as less than 5 lymph node metastases each smaller than 2mm in central compartment. Purpose : We evaluated the number of positive nodes, Positive node ratio (PNR), recurrence, and radioablation therapy. Also, evaluated the safety of omitting strategy of radioablation after total thyroidectomy with PTC, espe-cially on low-PNR N1a patients compared with high-PNR N1a patients.
Methods
: Consecutive 147 N1a and 216 N0 patients who underwent total thyroidectomy with central neck dissection between 2003 and 2004 were enrolled. We divided 147 N1a patients into two groups, such as 96 high-PNR versus 51 low-PNR group according to 50% of PNR, and compared these two groups with N0 group.
Results
7.2% (26/363) recurrences were occurred, and 21/147 (14.3 %) recurrences were on N1a patients, and 5/216 (2.3 %) were on N0 patients. Of these 21 recurrences in N1a stage patients, 20 (95.2 %) recurrences were occurred in high-PNR N1a group and only 1 (4.8 %) recurrence was in low-PNR N1a group. The recurrence of low-PNR N1a group was significantly lower than high-PNR N1a group (Log-rank p value = 0.003), but sig-nificantly not different from N0 group (Log-rank p value = 0.889). Although this study was a retrospective non-randomized trial with small number of patients, the 10-year recurrence of omitting RAI in low-PNR N1a patients with less than 50% of PNR were shown to be comparable with 216 N0 low risk patients.
Conclusion
: Positive node ratio could be a useful predictor of recurrence and useful guidance postoperative management -rather than absolute number of positive node.

Key Words: Papillary thyroid carcinoma, Risk assessment, Radioactive hazard release