Thyroid cancer natural history

Classification
Thyroid cancers can be classified according to their pathological characteristics. The following variants can be distinguished (distribution over various subtypes may show regional variation):
 * Papillary thyroid cancer (75%, incl. mixed papillary/follicular)
 * Follicular thyroid cancer (16%)
 * Medullary thyroid cancer (5-7%)
 * Anaplastic thyroid cancer (3%)
 * Lymphoma (1%)
 * Squamous cell carcinoma, sarcoma (0.5 - 2%)

Papillary thyroid cancer prognostic indicators
There are at minimum 13 known scoring systems for prognosis; some of these outright conflicting. Among the more often used are:
 * AGES - Age, Grade, Extent of disease, Size
 * AMES - Age, Metastasis, Extent of disease, Size
 * MACIS - Metastasis, Age at presentation, Completeness of surgical resection, Invasion (extrathyroidal), Size (this is a modification of the AGES system)
 * TNM - Tumor, node, metastasis. Remarkable about the TNM grading for (differentiated) thyroid carcinoma is that the scoring is different according to age.

Medullary Thyroid Carcinoma Prognostic Indicators
The prognostic value of measuring calcitonin and carcinoembryonic antigen (CEA) concentrations in the blood has been recently studied in a retrospective study of 65 MTC patients; see Barbet, et al. The post-surgical times ranged from 2.9 years to 29.5 years; all 65 patients continued to have abnormal calcitonin levels after total thyroidectomy and bilateral lymph node dissection. The prognosis of surviving MTC appears to be correlated with the rate at which a patient's postoperative calcitonin concentration doubles, rather than the pre- or postoperative absolute calcitonin level.

The result of the 65 patient study can be summarized with respect to the calcitonin doubling time (CDT):

CDT < 6 months: 3 patients out of 12 (25%) survived 5 years. 1 patient out of 12 (8%) survived 10 years. All died within 6 months to 13.3 years.

CDT between 6 months and 2 years: 11 patients out of 12 (92%) survived 5 years. 3 patients out of 8 (37%) survived 10 years. 4 patients out of 12 (25%) survived to the end of the study.

CDT > 2 years: 41 patients out of 41 (100%) were alive at the end of the study. These included 1 patient whose calcitonin was stable, and 11 patients who had decreasing calcitonin levels.

The 65 patients had a median age of 51 (range was 6 to 75), with 24 age 45 years or younger and 41 older than 45 years. The gender representation was 31 males and 34 females. All patients shared the following characteristics: 1) had total thyroidectomy and lymph node dissection; 2) had non-zero calcitonin levels after surgery; 3) had at least 4 serum calcitonin measurements after surgery; 4) had a status that could be confirmed at the conclusion of the study.

The same study noted that calcitonin doubling time is a statistically better predictor of MTC survival, compared with CEA.