Journal List > Int J Thyroidol > v.9(2) > 1082740

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

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.

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.
ijt-9-159f1.tif
Fig. 2.
Comparison of recurrence rate between patients with papillary thyroid carcinoma who had pathological N1a and N1b disease.
ijt-9-159f2.tif
Fig. 3.
Kaplan-Meier survival analysis according to patholo-gical N1a and N1b disease in patients with papillary thyroid carcinoma.
ijt-9-159f3.tif
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
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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