Differentiated thyroid cancer: determinants of disease progression in patients <21 years of age at diagnosis: a report from the Surgical Discipline Committee of the Children's Cancer Group.

OBJECTIVE: This study was done to define the extent of disease and evaluate the effect of staging and treatment variables on progression-free survival in patients with differentiated thyroid carcinoma who were less than 21 years of age at diagnosis.

SUMMARY BACKGROUND DATA: Differentiated thyroid cancer in young patients is associated with early regional lymph node involvement and distant parenchymal metastases. Despite this, the overall long-term survival rate is greater than 90%, which suggests that biologic rather than treatment factors have a greater effect on outcome.

METHODS: Variables analyzed for their impact on progression-free survival in a multi-institutional cohort of 329 patients included age, antecedent thyroid irradiation, extrathyroidal tumor extension, size, nodal involvement, distant metastases, technique of thyroid surgery and lymphatic dissection, initial treatment with 131Iodine, residual cervical disease, and histopathologic subtype. Surgical complications were correlated with the specific procedures completed on the thyroid gland or cervical lymphatics.

RESULTS: The overall progression-free survival rate was 67% (95%, CI: 61%-73%) at 10 years with 2 disease-related deaths. Regional lymph node and distant metastases were present in 74% and 25% of patients, respectively. Progression-free survival was less in younger patients (p = 0.009) and those with residual cervical disease after thyroid surgery (p = 0.001). Permanent hypocalcemia was more frequent after total or subtotal thyroidectomy (p = 0.001) while wound complications increased after radical neck dissections (p < 0.00001).

CONCLUSIONS: The progression-free survival rate was better after a complete resection and in older patients. Progression-free survival rate was the same after lobectomy or more extensive thyroid procedures, but comparison was confounded by the increased use of total or subtotal thyroidectomy in patients with advanced disease. The risk of permanent hypocalcemia increased when total or subtotal thyroidectomy was done. Thyroid lobectomy alone may be appropriate for patients with small localized lesions while total or subtotal thyroidectomy should be considered for more extensive tumors.