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S. Dermody et al. / International Journal of Pediatric Otorhinolaryngology 89 (2016) 121 e 126

Fig. 4. Fifteen year disease speci fi c survival after surgery and radiation therapy for each subtype based on extent of disease between 2007 and 2012 (A: Papillary, B: Follicular, C: Medullary, D: Papillary follicular; blue: Localized at initial diagnosis, orange: Distant metastases at initial diagnosis). (For interpretation of the references to colour in this fi gure legend, the reader is referred to the web version of this article.)

disease speci fi c survival demonstrated signi fi cant bene fi t when adjuvant radioactive iodine uptake was instituted in the course of treatment. Interestingly, the medullary thyroid subtype demon- strated some bene fi t with external beam radiation therapy, but since the cells that constitute the medullary thyroid carcinoma do not uptake iodine, there does not appear to be the same improvement in disease speci fi c survival when compared to the papillary or follicular subtypes when utilizing I 131 isotopes. For pediatric patients diagnosed with papillary follicular variant thy- roid carcinoma, there was no statistically signi fi cant difference in survival between those who underwent surgery or surgery with adjuvant radioactive iodine uptake therapy at fi fteen years post- diagnosis. It is possible that true differences are dif fi cult to discriminate because survival of both groups is excellent, or perhaps survival outcomes must be analyzed at a later time point, beyond fi fteen-years, to identify a statistically signi fi cant bene fi t in terms of disease speci fi c survival. Lastly, our group evaluated the differences in fi fteen-year dis- ease speci fi c survival in pediatric patients diagnosed with localized or distant metastatic disease at initial evaluation and were subse- quently treated with surgery with adjuvant radiation. Overall, pa- tients who demonstrated localized involvement at initial diagnoses maintained statistically better fi fteen-year disease speci fi c survival at each year, while patients who presented with distant metastases at initial diagnosis demonstrated poorer outcomes regardless of each subtype. The juxtaposition between survival outcomes in pediatric patients with localized involvement compared to those with distant metastases at initial diagnosis is most apparent for medullary thyroid carcinoma, where approximately only fi fty percent of the original patient cohort with distant metastases survived fi fteen years post-diagnosis ( Fig. 4 ). Fortunately, a diag- nosis of localized or distant metastatic disease in the papillary, follicular, and papillary follicular variant subtypes maintained excellent outcomes after surgery and adjuvant radioactive iodine uptake therapy. Based on our group's analysis of the most recently available data from the SEER database, the survival outcomes amongst patients with papillary, follicular and papillary follicular variants reach up- wards of 95% at fi fteen years post-diagnosis, illustrating that the

current treatment regimes afford the pediatric population with excellent survival outcomes. However, medullary thyroid carci- noma continues to demonstrate less desirable outcomes, especially if one presents with metastatic disease at initial diagnosis. The SEER database has several limitations that must be addressed when evaluating this manuscript. Overall, the database retrospectively reviews patient incidence and disease speci fi c sur- vival when it is uploaded to the National Cancer Institute's database and thus, this study maintains all of the typical biases associated with a retrospective analysis and possible coding errors. Further- more, the database does not present perineural invasion or recur- rence data, which could affect the survival outcomes of the patients that it reports, especially since recurrence is common in the pedi- atric population. It is also important to note that the database does not specify which patients underwent prophylactic total thyroid- ectomy for the medullary carcinoma subtype and thus may have skewed the disease speci fi c survival to more improved disease speci fi c survival as reported within this study. Based on the current literature, it is undetermined if neck dissection provides bene fi t to pediatric patients; however, based on the search query, the SEER database limits users to total thyroidectomy without knowledge if a neck dissection was performed. Even with these limitations, the SEER database is the gold standard in obtaining surveillance data for the multitude of cancer diagnoses in both the pediatric and adult populations. While thyroid cancer is a dif fi cult diagnosis to provide to both pediatric patients and families, survival outcomes are excellent if identi fi ed before the teenage years. According to our analysis of the most recent data available through the SEER database, the current treatment modalities utilized provide pediatric patients with greater than 95% survival for the most common thyroid carcinoma subtypes, excluding medullary thyroid carcinoma. This study demonstrates that the incidence of pediatric thyroid cancer has continued to increase by approximately one percent yearly be- tween 2007 and 2012, but the overall outcomes remain very favorable. 5. Conclusion

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