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Management of Papillary Thyroid Cancer

Management of Papillary Thyroid Cancer

Dr. Vassilopoulou-Sellin begins her discussion advocating near total thyroidectomy with post-operation radiation iodine ablation for most patients. This is a thesis that can be questioned in terms of the numerous studies in recent years about risk group [1-4] analysis and the ability to sort out the vast majority of patients who have essentially no risk of ever dying of disease from those few patients, generally older, who have a very significant risk of dying of disease.

As in other areas of surgical cancer management, there should be attempts to "make the punishment fit the crime." That is, if a cancer can be reliably distinguished to have a mortality rate at 20 years of 1% or less, there hardly seems need to embark on radical therapy for its management. On the other hand, cancers that have a 50% or 70% mortality rate certainly deserve the utmost in radical therapy, whether that can actually make a difference in their survival or not, since little is to be lost by rigorous and risky attempts at control in such patients.

The author spends considerable time describing epidemiology and etiology related to low-dose radiation in childhood. Almost all such radiation, which became common in the 1930s and 1940s, had completely stopped by the mid 1950s. Thus, we are 40 years from the time when the relationship between childhood radiation and later thyroid cancer was reported and the cessation of almost all programs of such radiation for tonsil, adenoid, and thymus enlargement. It is very uncommon to see patients today who have any history of childhood radiation.

The author correctly points out that there is a heightened risk of papillary thyroid cancer in children or young adults who receive therapeutic radiation for Hodgkin's disease or other cancers. Such patients should be followed by clinical examinations, but not by more elaborate diagnostic studies, for any signs of a palpable mass that may require aspiration cytology to rule out papillary thyroid cancer.

There is no evidence in the literature that radiation-associated papillary thyroid cancer has any different clinical course than papillary thyroid cancer not associated with radiation therapy. Therefore, since the occurrence is almost entirely in young children and adults, they almost exclusively fit in the "low-risk" category of patients, and have essentially no mortality from papillary thyroid cancer.

The author points out that many adults present with cervical lymph node metastases. What is not noted is that these cervical lymph nodes are common in patients up to the age of 40 or 50, but uncommon in thyroid cancer over the age of 50. Thus, the very patients that seem to do best with surgery for their papillary thyroid cancer have the highest incidence of lymph node metastases and, conversely, "high-risk" patients do not generally have lymph node metastases.

The Importance of Needle Biopsy

Practitioners need to bear in mind that one of the causes of enlarged cervical lymph nodes in young people is papillary carcinoma of the thyroid. A needle aspiration cytologic diagnostic study of these nodes is as appropriate as needle aspiration of a thyroid nodule for detection of disease. Unfortunately, many young patients are referred directly to open excision of a palpable cervical node without a prior needle biopsy. Any enlarged cervical lymph node in a child or young adult should first be subjected to needle aspiration, which usually will confirm a diagnosis of papillary carcinoma of the thyroid, and/or will suggest the diagnosis of lymphoma, which then may lead to further nodal tissue excision. In this fashion, inappropriate open node biopsies can be avoided in thyroid carcinoma.

The author discusses the various other tests for the analysis of thyroid nodules, but it should be kept in mind that thyroid cancer is an anatomic disease and has no functional correlates. Therefore, studies of thyroid function have no role in initially analyzing thyroid nodules. As she states, the most appropriate current management of a thyroid nodule is first fine needle aspiration cytology, and only later, if the lesion is found not to be suspicious or malignant, should other diagnostic tests be considered. Indeed, ultrasound is no more reliable in diagnosing cysts than a needle aspiration, and much more expensive.

Fine needle aspiration of a thyroid mass should yield reports characterized as (1) malignant, (2) suspicious, (3) benign, or (4) inconclusive. Patients with inconclusive fine needle aspiration make up roughly 15% of cases, and can be subjected either to repeat fine needle aspiration or other diagnostic tests as the clinical situation warrants. All "suspicious" fine needle aspirations consist of follicular cells, which cannot distinguish between a follicular nodule in an adenomatous goiter, a follicular adenoma, or a follicular adenocarcinoma, as the histology of individual cells does not determine the diagnosis of cancer in endocrine lesions. The location of the cells obtained makes the diagnosis of cancer, such as capsular, or vascular invasion, or nodal metastases. Thus, all suspicious follicular lesions should be excised. Papillary carcinoma, however, is usually accurately diagnosed by needle aspiration cytology.

The Sequence of Diagnostic Steps

Initial needle aspiration cytology minimizes costs, gives specific histologic information, and makes the most efficient initial evaluation of thyroid nodules. A well-established algorithm for evaluating thyroid nodules would consist of, first, fine needle aspiration after palpation of the nodule. Second, careful assessment of the cytology, followed by surgical excision of malignant or suspicious nodules, or clinical evaluation of the thyroid situation if a benign nodule is confirmed by FNA. The next decision would be whether to pursue functional tests or further anatomic tests in what generally are small nodules in an adenomatous goiter. If the benign FNA is consistent with an adenomatous nodule or adenomatous goiter, and the patient does not have a cosmetically or symptomatically significant nodule, and is functionally euthyroid, nothing further need be done.

The most important step in the current management of the usual papillary carcinoma of the thyroid is to assign the patient to a clinical risk group category. A number of investigators have carefully defined such risk categories, which separate patients with papillary carcinoma of the thyroid that carries almost no lethal implications (the overwhelming majority of patients) from the few, generally older, patients who have high-risk disease that may need more aggressive treatment [1-4].

The Good Risk Group

The Mayo Clinic authors [2,4] have determined that 85% of patients fit into the clinical risk category that has a 1% 20-year mortality and a 3% 10-year recurrence rate. Such patients do not need radioactive iodine at any time in their management and do not need total thyroidectomy. This is particularly true given the small size of thyroid nodules palpated in a contemporary medical practice in this country. We have shown that more than 60% of current patients with thyroid cancer have lesions less than 2 cm in maximum diameter [1].

Risk group assessment of thyroid cancer is based largely on age, but also on extra-glandular extension, completeness of surgical removal, and the presence or absence of chest x-ray evidence of pulmonary metastases. Such risk group definition (AMES [age, metastases, extent, size] [1], AGES [age, grade, extent, size] [2], MACES [metastases, completion of surgery, extent, size] [4]) is extremely accurate prognostically.

Indications for Total Thyroidectomy

Childhood papillary thyroid carcinoma frequently presents with bulky cervical lymph nodes, and consideration should be given to doing a total thyroidectomy and functional neck dissection, since there is a need to screen for and treat pulmonary metastases. Children with papillary carcinoma of the thyroid commonly present with pulmonary metastases today and, as Dr. Vassilopoulou-Sellin states, can almost always be controlled with radioactive iodine.

Women over the age of 50 or men over the age of 40 or who fit into a "high-risk" category as defined by one of the systems published, should have a total or near-total thyroidectomy in order to maximize the effectiveness of radioactive iodine, which may well be used. Except for those two categories, no other patients currently need routine total thyroidectomy since radioactive iodine is not necessary in low-risk patients.

In the 85% of patients who have only a 1%, 20-year mortality, there is no need for detailed postoperative follow up studies. The use of thyroglobulin is not necessary, nor are frequent radioactive scans as follow-up procedures after total thyroid ablation. Such scans cannot be justified considering the numerous episodes of hypothyroidism necessary to achieve adequate imaging on radioactive scans, the fact that recurrences are very uncommon, and the treatability of such recurrences when they do occur. Indeed, more than two-thirds of recurrent papillary carcinoma of the thyroid in young adults and low-risk groups consists of cervical lymph node metastases, which have no adverse prognostic implications. If cervical lymph nodes become palpable later on, they can be man- aged by a function-preserving neck dissection.

It is important to emphasize that appropriate treatment of papillary carcinoma of the thyroid can be determined by clinical assessment and definition of risk group after initial assessment by fine-needle aspiration, and conservative surgical excision of appropriate candidates. Such a rational, conservative, approach minimizes risks of complications and, in the vast majority of patients, eliminates the need for detailed postoperative follow-up.

References

1. Cady B, Rossi R: An expanded view of risk-group definition in differentiated thyroid carcinoma. Surgery 104(6):947-953, 1988.

2. Hay ID, Grant CS, Taylor WF, et al: Ipsilateral lobectomy versus bilateral lobar resection in papillary thyroid carcinoma: A retrospective analysis of Surgical outcome using a novel prognostic scoring system. Surgery 102:1088-1094, 1987.

3. Shah JP, Loree TR, Dharker D, et al: Prognostic factors in differentiated carcinoma of the thyroid gland. Am J Surg 164:658-661, 1992.

4. Hay ID, Bergstralh EJ, Goellner JR, et al: Predicting outcome in papillary thyroid carcinoma: Development of a reliable prognostic scoring system in a cohort of 1779 patients surgically treated at one institution during 1940-1989. Surgery 114(6):1050-1057

 
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