I-131, Thyroidectomy, Staging and Thyroid Cancer Survival
Thyroidectomy, I-131, Staging and Thyroid Cancer Survival

Thyroid Cancer Treatment:

The treatment of thyroid cancer always involves removing the thyroid gland.  In patients who are under 45 years of age with a very small tumor which is not diagnosed at the time of surgery - observation and thyroid suppression with thyroxin is sometimes considered. 

If cancer is known to be present at the time of surgery, a total thyoidectomy is usually performed.  A subtotal resection will not allow the patient to be followed with serum thyroglobulins and if I-131 treatment is indicated a larger total dosage must be given. 

Thyroglobulin is produced by the thyroid.  In patients who have had a total thyroidectomy, the value of this blood test should be zero.  If it is not, thyroid cancer may be somewhere in the patient.  (Note:  If the patient has thyroid antibodies, they will bind to thyroglobulin and invalidate the test.)

The thyroid gland uses iodine to make thyroid hormone.  The gland binds iodine.  If a patient is given radioactive iodine, the gland will uptake the compound and concentrate thyroxin in the thyroid cells.   The same is true for differentiated thyroid cancer.  This delivers a highly concentrated and localized dosage of irradiation that kills both normal thyroid cells and cancer cells.   However, normal cells take up I-131 much more readily than the cancer.  If any part of the thyroid gland is left, it must first be ablated.  This increases the total dosage which the patient is given.

 I-131 is used to treat advanced differentiated thyroid cancer and cancer with distant metastasis.  In lower doses it is also used to scan the patient for distant metastases.

There is a total lifetime dosage of I-131 which can be given to the patient.  In addition, I-131 may rarely cause the cancer to dedifferentiate and become more aggressive.  Some patients who receive I-131 may developed a dry cough and dry mouth. 

A modified neck dissection involves the removal of lymph nodes from around the thyroid gland, the carotid artery, and posterior neck.  It should be done if: 

  1. The patient has known lateral disease.
  2. The patient has medullary carcinoma.  Medullary carcinoma has a very high rate of neck metastasis.   

A modified neck dissection should be considered in:

  1. Patients older than 60 years.
  2. Patients whose cancer has spread beyond the capsule of the thyroid gland. 
  3. Primary tumors whose size is greater than 4 cm.
  4. Aggressive tumors -- Hurthle cell, insular and poorly differentiated.  Some feel surgery is not indicated for anaplastic tumors because of the very poor prognosis.

Thyroid Cancer Staging:
Thyroid cancer is the only cancer where the patient's age is a variable in determining the stage or extent of the disease.

Thyroid cancer can be divided into three types:  Differentiated Cancers (papillary or follicular), Medullary Carcinoma, Undifferentiated/Anaplastic Carcinoma.

Differentiated (Papillary and Follicular) Thyroid Cancer

  • If the patient's age is below 45 there is no Stage III or IV, even with spread to the lungs there is a 95% survival rate. 
    -- Stage I:  Any size tumor with any number and size of lymph nodes -- No distant spread.
    -- Stage II:  Distant spread or metastasis. 
  • If the patient is 45 years of age or older:
    -- Stage I:  Tumor is less than 2 cm and has not spread to lymph nodes (T1,N0,M0)
    -- Stage II:  Tumor is 2 to 4 cm and has not spread to lymph nodes (T2,N0,M0)
    -- Stage III:  Tumor is larger than 4 cm and confined to the thyroid or has spread to neck nodes next to the thyroid (T3,N0,M0; T1-3, N1b, M0)
    -- Stage IV:  IVa:  Tumor spread beyond the thyroid or tumor spread to nodes in the lateral neck or upper chest;  
    IVb: Tumor grown into the spine or nearby major blood vessels (carotid or jugular vein)
    IVc:  Tumor has distant metastasis

Medullary Carcinoma

  • Staging is the same as Differentiated Carcinoma in a 45 year old patient.

Anaplastic/Undifferentiated Carcinoma

  • All are Stage IV

Thyroid Cancer Survival:  The five year survival rates are the percentage of patients who survive 5 years after diagnosis of thyroid cancer.  These rates do not include patients who die from unrelated causes. 

Stage Papillary* Follicular* Medullary Anaplastic/
I 100 % 100 % 100 % XXX
II 100 % 100 % 79 % XXX
III 96 % 79 % 78 % XXX
IV 45 % 47 % 24 % 9 %

* Patients under 45 years of age are only Stage I and II. 

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