Thyroid carcinoma is the third most common tumor malignancy in children. This pediatric cancer shares several characteristics with adult thyroid cancer patients including common cellular subtypes that are papillary, follicular and medullary; a female to male ratio is approximately 6:1; and a cervical nodal disease that can be observed at the time of presentation in 30-60 percent in both papillary and follicular malignancies.
While the long-term survival of pediatric thyroid carcinoma is purportedly excellent, there have been few large studies identifying clinical outcomes of this childhood malignancy. Most studies have been comprised of single-institution reviews. Multiple institutional studies have occurred but efforts to create a larger database may be limited by institutional or regional bias. The sample size limitations in these studies, coupled with the need for long-term follow-up of a disease with a slow rate of recidivism, have resulted in difficulties in assessing positive and negative predictive outcomes for treatment.
Two otolaryngologist—head and neck surgeons set out to identify such outcome variables through following large numbers of patients over a long period of time should be analyzed which avoid institutional and regional bias. They examined a large national database over a 12-year period in an effort to better understand long-term clinical outcomes of this indolent, although occasionally fatal, disease on a national level in the pediatric population. The length of this study avoided inherent biases in this type of research.
The authors of “Population-based Outcomes for Pediatric Thyroid Carcinoma,” are Nina L. Shapiro MD, Division of Head and Neck Surgery, UCLA School of Medicine, Los Angeles, CA; and Neil Bhattacharyya MD, at the Division of Otolaryngology, Brigham and Women’s Hospital, and the Department of Otology and Laryngology, Harvard Medical School, Cambridge, MA. Their findings are to be presented at the 19th Annual American Society of Pediatric Otolaryngology http://www.aspo.us/ meeting being held May 2-3, 2004, at the JW Marriott Desert Ridge Resort & Spa in Phoenix, AZ.
Methodology: The Surveillance, Epidemiology, and End Results (SEER) database (1988-2000) was reviewed, extracting all pediatric patients with thyroid carcinoma according to the following criteria: (1) Age at diagnosis ranging from birth to 18 years; (2) Primary extension of malignant thyroid tumor; (3) Well-differentiated thyroid carcinoma (papillary or follicular) and (4) Year of diagnosis between 1988 and 2000. Patients with alternative tumor types such as anaplastic or medullary carcinoma were excluded. Clinical and tumor-specific data extracted from the database included age at diagnosis, gender, tumor histology, tumor size, extent of primary site disease, extent of nodal disease, treatment with surgery and/or radioactive iodine, and survival statistics.
Data were tabulated and imported into SPSS version 10.0. From the of disease variables, the extent of primary site disease was staged as previously reported. Nodal disease was recorded as presence or absence of cervical nodes at the time of initial diagnosis. The extent of primary site surgical therapy was classified as biopsy only, lobectomy, subtotal thyroidectomy, or total thyroidectomy.
Results: The researchers identified 566 pediatric thyroid carcinomas in the 12-year period. The mean age at presentation was 16.0 years, with 84 percent of patients female. Tumor types consisted of 378 (66.8 percent) papillary carcinomas, 137 (24.2 percent) papillary carcinomas with follicular variant, and 51 (9.0 percent) follicular carcinomas. Overall, the average tumor size at presentation was 2.6 centimeters. With regard to primary disease site, the majority of patients (74.2 percent) had intrathyroidal disease alone. A small group had minor local extension (12.5 percent), and few had major or extravisceral extension (5.4 percent). Positive nodal disease in the neck was present in 37.1 percent of patients at initial diagnosis. The vast majority of patients were treated with total thyroidectomy (72.8 percent) followed by subtotal thyroidectomy (13.4 percent) followed by simple lobectomy (7.2 percent). Radioactive iodine treatment was administered to 51.4 percent of patients.
The overall survival for the entire group was 153.8 months, limited to 155 months of maximum follow-up. Papillary carcinomas (mean survival, 155.3 months) fared better than follicular carcinomas Patient age, presence of positive cervical nodes, extent of surgery, and use of radioactive iodine therapy did not significantly influence overall survival. The male gender, follicular histology, and initial local disease invasion had the most significant effects on decreasing long-term survival.
The results concur with the findings from other studies that state that pediatric thyroid carcinoma presents most commonly in the teenage years, and primarily in females. The most common histologic type is papillary, as is seen in the adult population. The distribution of nodal disease (37.1 percent) was also similar to that seen in prior studies. This research revealed that whereas treatment of the primary tumor ranged from simple lobectomy to total thyroidectomy, the extent of surgical intervention did not influence survival outcomes. This finding differs from several prior reports that describe superior outcomes in patients undergoing more radical resection such as sub-total or total thyroidectomy. Age at diagnosis, nodal status, and the addition of radioactive iodine therapy also had no significant influence on survival. Male gender, primary disease site extension, and follicular subtype all had negative prognostic influence on survival compared to other disease site variables.
Conclusions: Pediatric thyroid carcinoma exhibits excellent long-term survival outcomes. Patients with follicular variants demonstrate somewhat poorer outcomes than those with papillary variants. Although this disease is much more common in females than males, males with thyroid carcinoma have poorer outcomes than females. Locally advanced primary disease site extension also carries a poorer prognosis compared to intrathyroidal disease alone. While diagnostic work-up and management must be focused for each patient, accounting for potential short-and long-term morbidities, this new research offers current reference survival information for patients with pediatric thyroid carcinoma with respect to survival and clinical factors affecting outcome.