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Current Approaches to the Treatment of Well-Differentiated Thyroid Cancer

Current Approaches to the Treatment of Well-Differentiated Thyroid Cancer

The increasing frequency of diagnosis and death of
patients with follicular cell-derived carcinoma of the thyroid substantiates
the need for a broad understanding of the optimal diagnostic and treatment
strategies for this disease. Dr. Angelos has provided a good overview of the
treatment modalities and approaches to follow-up for these patients. However,
several points require additional emphasis or detail.

Prognosis and Staging

More than 1,200 patients die annually from follicular cell-derived
carcinoma or the complications of its treatment, with 10-year relative survival
rates of about 95% and 90% for papillary and nonoxyphilic follicular carcinoma,
respectively.[1,2] Recurrence rates are usually at least twice that of mortality
rates for these patients. Major prognostic factors at diagnosis associated with
increased risk for eventual disease-related mortality include larger tumor size,
invasion of the primary tumor into extrathyroidal tissues, extracervical
metastases, and older age.

Similarly, disease recurrence or progression is associated with these
parameters, but age is a double-edged sword; ie, the youngest patients
experience high recurrence and progression rates as well. Multiple minor factors
have also been identfied, but there exists far less agreement about the
importance of variables such as multifocality and locoregional nodal
involvement. Certain histologic subtypes may represent more aggressive disease;
eg, the tall cell variant of papillary carcinoma or the oxyphilic (Hürthle
cell) variant of follicular carcinoma.

Microscopic, immunohistochemical, and molecular features that have been
associated with a greater risk of either recurrence or death include increased
tumor vascularity, aneuploidy, increased epidermal growth factor (EGF)-receptor
and decreased thyroid-stimulating hormone (TSH)-receptor status, and the
presence of the ret/PTC3 oncogene isoform.[3] The variation in the appearance
and behavior of the various subtypes of follicular cell-derived carcinoma
makes the phrase "well-differentiated thyroid carcinoma" archaic and
may lead to underestimates of the potential for morbidity and mortality.

Whether to use prognostic staging and how to select among the various
approaches to staging remain significant challenges for the practicing
clinician. In addition to the three risk group classifications cited by Dr.
Angelos, numerous other approaches have been proposed, including those developed
by the American Joint Commission on Cancer (AJCC), European Organization for
Research and Treatment of Cancer (EORTC), Clinical Class, Ohio State University,
National Thyroid Cancer Treatment Cooperative Study, Mayo Clinic (MACIS, for
metastases, age, completeness of surgery, invasion of cancer, size), and Lahey
Clinic (AMES, for age, metastases, extent, size).[4] Two recent studies
demonstrated the superior predictive value of the AJCC approach compared
with the Clinical Class, Ohio State, MACIS, and AMES strategies, leading to
the widespread recognition and incorporation of the AJCC classification strategy
into two consensus treatment guidelines.[5,6]

Role of TSH-Suppression Therapy

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