Pathological N1b Node Metastasis Itself Can Be Still a Valid Prognostic Factor in PTC after High Dose RAI Therapy

Choon-Young Kim; Seung Hyun Son; Ji-hoon Jung; Chang-Hee Lee; Ju Hye Jeong; Shin Young Jeong; Sang-Woo Lee; Byeong-Cheol Ahn; Jaetae Lee

doi:10.11106/ijt.2016.9.2.159

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Kim, Son, Jung, Lee, Jeong, Jeong, Lee, Ahn, and Lee: Pathological N1b Node Metastasis Itself Can Be Still a Valid Prognostic Factor in PTC after High Dose RAI Therapy

Original Article

Int J Thyroidol 2016;9(2):159-167.

Published online: 20 November 2016

DOI: https://doi.org/10.11106/ijt.2016.9.2.159

Pathological N1b Node Metastasis Itself Can Be Still a Valid Prognostic Factor in PTC after High Dose RAI Therapy

Choon-Young Kim¹, Seung Hyun Son¹, Ji-hoon Jung¹, Chang-Hee Lee¹, Ju Hye Jeong¹, Shin Young Jeong¹, Sang-Woo Lee¹, Byeong-Cheol Ahn¹, Jaetae Lee^1,^2,

¹Department of Nuclear Medicine, Kyungpook National University Hospital, Kyungpook National University School of Medicine, Daegu, Korea

²The Daegu-Gyeongbuk Medical Innovation Foundation, Daegu, Korea

Correspondence: Jaetae Lee, MD, PhD, Department of Nuclear Medicine, Kyungpook National University Hospital, Kyungpook National University School of Medicine, 130 Dongdeok-ro, Jung-gu, Daegu 41944, Korea Tel: 82-53-420-5586, Fax: 82-53-200-3419, E-mail: jaetae@knu.ac.kr

Received 8 July 2016 Revised 12 October 2016 Accepted 15 October 2016

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background and Objectives

The aim of this study was to determine whether pathologically proven central or lateral lymph node (LN) metastasis (pN1a or pN1b) could affect ablation success and recurrence after high-dose radioactive iodine (RAI) ablation. We also sought to identify the risk factors for long-term recurrence in patients with papillary thyroid carcinoma (PTC).

Materials and Methods

A total of 277 patients with pN1 disease who had undergone high-dose RAI ablation (5.55 GBq) between 2000 and 2006 were included in this retrospective study. We compared the ablation success rate and the recurrence rate between patients with pN1a and pN1b disease. Univariate and multivariate analyses were performed to identify the risk factors for recurrence.

Results

The median duration of follow-up was 10.2 years. The overall ablation success rate was 64%, and the ablation success rate in the pN1b group (49%) was lower than in the pN1a group (74%). The overall recurrence rate was 23%, and the recurrence rate in the pN1b group (30%) was higher than in pN1a group (18%). A higher ratio of metastatic LNs, a higher level of pre-ablation thyroglobulin, and ablation failure were significant risk factors for recurrence by multivariate analysis.

Conclusion

Patients with pN1b disease experienced a lower ablation success rate and a higher recurrence rate than patients with pN1a disease. However, a higher ratio of metastatic LNs, a higher level of pre-ablation thyroglobulin, and ablation failure were stronger risk factors than the pathological N stage for long term recurrence in patients with node-positive PTC.

Keywords: Papillary thyroid carcinoma, Ablation success, Recurrence, Radioactive iodine ablation

References

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Fig. 1.

Comparison of ablation success rate between patients with papillary thyroid carcinoma who had pathological N1a and N1b disease.

Fig. 2.

Comparison of recurrence rate between patients with papillary thyroid carcinoma who had pathological N1a and N1b disease.

Fig. 3.

Kaplan-Meier survival analysis according to patholo-gical N1a and N1b disease in patients with papillary thyroid carcinoma.

Table 1.

Patient characteristics

Characteristics	All patients (n=277)	pN1a (n=167)	pN1b (n=110)	p value
Sex
Female	239 (86%)	153 (92%)	86 (78%)	0.003
Male	38 (14%)	14 (8%)	24 (22%)
Age (year)
＜45	158 (57%)	101 (61%)	57 (52%)	0.193
≥45	119 (43%)	66 (39%)	53 (48%)
Tumor size (cm)
Mean±SD	2.2±1.3	2.3±1.3	2.0±1.3	0.139
Median (range)	2.0 (0.1–7.0)	2.0 (0.2–7.0)	1.8 (0.1–6.0)
ETE
Intrathyroidal	80 (29%)	54 (33%)	26 (24%)	0.119
Microscopic ETE	83 (30%)	49 (29%)	34 (31%)
Macroscopic ETE	114 (41%)	64 (38%)	50 (45%)
Pathological T stage
T1	56 (20%)	34 (20%)	22 (20%)	0.184
T2	21 (8%)	18 (11%)	3 (3%)
T3	154 (55%)	92 (55%)	62 (56%)
T4	46 (17%)	23 (14%)	23 (21%)
Number of dissected LNs
Mean±SD	15±13	7±4	27±14	＜0.001
Median (range)	9 (3–76)	6 (3–22)	27 (3–76)
Number of metastatic LNs
Mean±SD	5±5	3±2	8±6	＜0.001
Median (range)	4 (1–30)	3 (1–12)	7 (1–30)
Ratio of metastatic LNs
Mean±SD	0.4±0.3	0.5±0.3	0.3±0.2	＜0.001
Median (range)	0.3 (0.02–1.0)	0.4 (0.06–1.0)	0.3 (0.02–1.0)
Pre-ablation s-Tg (ng/mL)
Mean±SD	26.4±65.6	19.6±58.3	36.8±74.5	0.043
Median (range)	5.4 (0.1–470.0)	3.4 (0.1–470.0)	8.6 (0.1–433.9)
Post-therapy I-131 WBS
Thyroid bed	219 (79%)	140 (83%)	79 (72%)	0.011
LN metastasis	54 (20%)	26 (16%)	28 (25%)
Distant metastasis	4 (1%)	1 (1%)	3 (3%)

ETE: extrathyroidal extension, LN: lymph node, s-Tg: TSH-stimulated thyroglobulin, SD: standard deviation, WBS: whole body scan

Table 2.

Univariate and multivariate analyses of clinicopathologic variables for recurrence-free survival in patients with node-positive papillary thyroid carcinoma

Variables	Univariate analysis			Multivariate analysis
Variables	HR	95% CI	p value	HR	95% CI	p value
Sex
Female
Male	1.47	0.8–2.7	0.232
Age (year)
＜45
≥45	1.21	0.7–2.0	0.443
Tumor size (cm)
≤4
＞4	1.70	0.8–3.4	0.155
ETE
Intrathyroidal/microscopic ETE
Macroscopic ETE	1.64	1.0–2.7	0.049
Pathological T stage
pT1-T3
pT4	2.02	1.2–3.5	0.013
Pathological N stage
pN1a
pN1b	1.85	1.1–3.0	0.015
Number of metastatic LNs
≤5
＞5	2.24	1.4–3.7	0.001
Ratio of metastatic LNs
≤0.4
＞0.4	2.43	1.5–4.0	＜0.001	1.77	1.1–3.0	0.031
Pre-ablation s-Tg (ng/mL)
≤10
＞10	4.35	2.6–7.3	＜0.001	2.11	1.1–3.9	0.020
Ablation success
Success
Failure	5.09	2.9–8.7	＜0.001	3.12	1.7–5.9	＜0.001

CI: confidence interval, ETE: extrathyroidal extension, HR: hazard ratio, LN: lymph node, s-Tg: TSH-stimulated thyroglobulin

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