[Predictive analysis of distant metastasis after primary treatment of papillary thyroid cancer in patients under 18 years old]

Objective: To investigate the distant metastasis after primary treatment of papillary thyroid cancer (PTC) in children and adolescents. Methods: A retrospective analysis of 180 cases (54 boys and 126 girls, with an age range of 6-18 years) with PTC treated at the Chinese Medical Academy Cancer Hospital and Zhejiang Cancer Hospital from January 1, 2001 to December 31, 2014 was performed. Patients' clinical and pathological data were collected. The follow-up results were statistically analyzed. The distant metastasis rate during the follow-up period was analyzed by the Kaplan-Meier method. Log-Rank test was used for univariate analysis and Cox regression model was established in multivariate analysis. Results: Twenty-four cases (13.3%) had distant metastases during following-up with a median of 92 months. The Log-Rank test showed that the younger age ≤15 years old (χ(2)=11.803, P=0.001), the larger tumor diameter >20 mm (χ(2)=5.776, P=0.016), multifocal (χ(2)=11.205, P=0.001), bilateral tumor distribution (χ(2)=19.804, P=0.001), invaded capsule (χ(2)=10.808, P=0.001), and bilateral lymph nodes metastasis (χ(2)=6.278, P=0.012) were risk factors for distant metastasis after initial treatment. The Cox regression analysis showed that age ≤15 years (hazard ratio [95% confidence interval]: 4.08[1.504-11.111], P=0.006) and bilateral tumor distribution (hazard ratio [95% confidence interval]: 4.77[1.903-11.966], P=0.001) were independent risk factors for distant metastasis after initial treatment. The risk factors for local recurrence and distant metastasis were similar, but the local recurrence could not be a significant predictor for distant metastasis. It was indicated that distant metastasis rate was lower in patients with total thyroidectomy in multifocal lesions groups (χ(2)=5.891, P=0.015). Conclusions: Age, tumor size, invaded capsule, bilateral lymph nodes metastasis, multifocal and bilateral lesions are factors for predicting distant metastasis after primary treatment of PTC in children and adolescents. Total thyroidectomy is recommended for patients with multifocal and bilateral lesions.