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disease specific survival demonstrated significant benefit when
adjuvant radioactive iodine uptake was instituted in the course of
treatment. Interestingly, the medullary thyroid subtype demon-
strated some benefit 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 specific survival when compared to the
papillary or follicular subtypes when utilizing I131 isotopes. For
pediatric patients diagnosed with papillary follicular variant thy-
roid carcinoma, there was no statistically significant difference in
survival between those who underwent surgery or surgery with
adjuvant radioactive iodine uptake therapy at fifteen years post-
diagnosis. It is possible that true differences are difficult to
discriminate because survival of both groups is excellent, or
perhaps survival outcomes must be analyzed at a later time point,
beyond fifteen-years, to identify a statistically significant benefi t in
terms of disease specific survival.
Lastly, our group evaluated the differences in fifteen-year dis-
ease specific 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 fifteen-year disease specific 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 fifty
percent of the original patient cohort with distant metastases
survived fifteen 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 fifteen 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 specific 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 specific survival to more improved disease
specific survival as reported within this study. Based on the current
literature, it is undetermined if neck dissection provides benefit 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.
5. Conclusion
While thyroid cancer is a difficult diagnosis to provide to both
pediatric patients and families, survival outcomes are excellent if
identified 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.
Fig. 4. Fifteen year disease specific 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 figure
legend, the reader is referred to the web version of this article.)
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