Medicine by Alexandros G. Sfakianakis,Anapafseos 5 Agios Nikolaos 72100 Crete Greece,00306932607174,00302841026182,email@example.com
Staging and Prognosis
TABLE 1: AJCC/UICC staging of thyroid cancer
Unlike most other cancers, in which staging is based on the anatomic extent of disease, the American Joint Committee on Cancer (AJCC) and International Union Against Cancer (UICC) staging of thyroid cancer also takes into consideration patient age at the time of diagnosis and tumor histology (Table 1).
Differentiated thyroid cancers
Recurrence and death following initial treatment of differentiated thyroid cancer can be predicted using a number of risk-classification schemes. Some commonly used systems are Tumor Node Metastasis (TNM) or Metastases, Age, Completeness of Resection, Invasion, Size (MACIS); the AMES (age, metastases, extent, and size) and AGES (age, grade, extent, and size) classifications; and then an additional clinicopathologic staging system, such as the American Thyroid Association (ATA) system, to estimate the risk of recurrence.
Low-risk patients are generally those younger than 45 years with low-grade nonmetastatic tumors that are confined to the thyroid gland and are less than 1 to 5 cm. Low-risk patients enjoy a 20-year survival rate of 97% to 100% after surgery alone.
High-risk patients are those 45 years and older with a high-grade, metastatic, locally invasive tumor in the neck or with a large tumor. Large size is defined by some authors as more than 1 cm and by others as more than 2 or more than 5 cm. The 20-year survival rate in the high-risk group drops to between 54% and 57%.
Intermediate-risk patients include young patients with a high-risk tumor (metastatic, large, locally invasive, or high grade) or older patients with a low-risk tumor. The 20-year survival rate in this group of patients is approximately 85%. Increasing age and tumor size, male sex, poorly differentiated carcinoma, lymph node involvement, and regional and metastatic disease were associated with increased cumulative incidence of death resulting from thyroid cancer.
Medullary thyroid carcinoma
Medullary thyroid carcinoma is associated with an overall 10-year survival rate of 40% to 60%. When medullary carcinoma is discovered before it becomes palpable, the prognosis is much better: patients with stage I medullary tumors (ie, tumors ≤ 2 cm or nonpalpable lesions detected by screening and provocative testing) have a 10-year survival rate of 95%.
Stage II medullary cancers (tumors 2 cm but 4 cm) are associated with a survival rate of 50% to 90% at 10 years. Patients who have lymph node involvement (stages III and IVA disease) have a 10-year survival rate of 15% to 50%. Unfortunately, approximately 50% of patients have lymph node involvement at the time of diagnosis.
When there are distant metastases (stages IVB and IVC), long-term survival is compromised. In patients with metastatic medullary thyroid cancer, the disease often progresses at a very slow rate, and patients may remain alive with disease for many years. Doubling time of calcitonin and CEA are predictive of prognosis. In a 2005 study by Barbet et al of patients with medullary thyroid cancer, those with a calcitonin doubling time of 6 months had a survival of 25% at 5 years and 8% at 10 years versus 100% survival among patients with a calcitonin doubling time of 2 years. The 2009 ATA management guidelines for medullary thyroid cancer recommend monitoring of doubling time of CEA and calcitonin. Frequency of surveillance has been recommended on the basis of the doubling time calculation for calcitonin and CEA. Patients with calcitonin or CEA doubling times of 2 years typically do not require systemic therapy, and such treatment should only be initiated after thorough discussion with the patient. Patients with rapidly progressing disease (doubling times of 2 years) should be considered for treatment.
The ATA website has a calculator for CEA and calcitonin doubling time.
Sidebar: Ho et al recently reported on a postoperative nomogram for predicting cancer-specific mortality in medullary thyroid cancer. The authors identified a total of 249 patients with medullary thyroid cancer managed entirely at one institution between 1986 and 2010. Patient, tumor, and treatment characteristics were recorded from patient charts. A risk model was then built to predict the 10-year cumulative incidence of medullary thyroid cancer. All predictors of interest were added in the starting full model before selection, including age, gender, preoperative and postoperative serum calcitonin, preoperative and postoperative CEA, RET mutation, perivascular invasion, margin status, M status, pathologic N status, and pathologic T status. Of 249 patients, 22.5% (56 of 249) died from medullary thyroid cancer, while 6.4% (16 of 249) died secondary to other causes. The mean