Cancer Recurrence

Certain factors can predict how, on average, well-differentiated thyroid cancer will progress. These prognostic indicators include the patient’s age at diagnosis, gender, and history of irradiation; certain characteristics of the tumor itself; and the way the cancer is managed, including the length of time between detection of the tumor and treatment.^1-5

Although the long-term survival rate for patients diagnosed with well-differentiated thyroid cancer is generally quite good, tumor recurrence is common, affecting up to 30% of patients, sometimes even decades after initial therapy.^[6,7,8] These recurrences are often treatable, if detected early and managed appropriately. Despite the generally favorable prognosis for most well-differentiated thyroid cancer patients, there are still approximately 1,500 thyroid cancer deaths each year7 in the United States,^[9] about three-fourths of which are from well-differentiated thyroid cancer.^[10]

There is a well-documented higher risk of recurrent tumor associated with delay of primary diagnosis and treatment,^[6] and it is logical that delay in finding recurrent tumor is also likely associated with worse clinical outcome. It is critical that thyroid cancer patients undergo regular, lifelong monitoring. Routine follow-up procedures vary with patient age, extent of surgical resection, and primary tumor characteristics (size, histological type, extent of local invasion, and presence of metastatic disease or multifocality), as well as findings from clinical assessments such as ultrasound, chest x-ray, positron emission tomography (PET), computerized tomography (CT) scanning, and magnetic resonance imaging (MRI).

Generally, clinicians agree that whole-body scans (WBS), neck ultrasound exams and serum thyroglobulin (Tg) testing are the most commonly used tests to monitor for thyroid cancer recurrences. Management guidelines published in 2006 by the American Thyroid Association provide an excellent summary.^[11] For more information on how Thyrogen^® (recombinant human thyroid stimulating hormone [rhTSH]) can enhance the sensitivity and accuracy of follow-up testing, please visit the About Thyrogen section of this website.

Traditionally, in order to conduct whole body scanning (WBS) and to achieve optimal sensitivity in thyroglobulin (Tg) testing, patients were required to remain hypothyroid until endogenous TSH levels rose above 25-30 mU/L. To accomplish this, deprivation of thyroid hormone therapy (THT) is required for 2 to 6 weeks (typically, the thyroxine [T4] supplement is withdrawn for 2 to 6 weeks before testing and/or the triiodothyronine [T3] supplement is withdrawn 2 to 3 weeks before testing). As a result, patients become hypothyroid.

Symptoms of hypothyroidism, which can include extreme fatigue, depression, and concentration deficit, may result in a major disruption of the patient's family, social and work life. Symptoms may persist for up to 10 weeks or more between initial withdrawal and restoration of normal thyroid hormone levels.^[12,13] More recent data highlight physiologic complications in patients with co-existing illness who become hypothyroid,^[14,15,16] as well as safety considerations for hypothyroid patients (a recent survey revealed that 1/3 of thyroid cancer patients admitted to driving an automobile while hypothyroid despite the medical advice of their physicians).^[16]

REFERENCES:

1. Sellers M, Beenken S, Blankenship A, et al. Prognostic significance of cervical lymph node metastases in differentiated thyroid cancer. Am J Surg. 1992;164:578-581.

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

3. Coburn MC, Wanebo HJ. Prognostic factors and management considerations in patients with cervical metastases of thyroid cancer. Am J Surg. 1992;164:671-676.

4. Ruiz-Garcia J, Ruiz de Almodóvar JM, Olea N, et al. Thyroglobulin level as a predictive factor of tumoral recurrence in differentiated thyroid cancer. J Nucl Med. 1991;32:395-398.

5. Mazzaferri EL, Jhiang SM. Long-term impact of initial surgical and medical therapy on papillary and follicular thyroid cancer. Am J Med. 1994;97:418-428.

6. Mazzaferri EL. An overview of the management of papillary and follicular thyroid carcinoma.

Thyroid.1999; 9:421-427.

7. Schlumberger M et al. Follow-up of low-risk patients with differentiated thyroid carcinoma: a European perspective. Eur J Endocrinol 150 (2):105-112, 2004.

8.Kloos R & Mazzaferri E. A single recombinant human thyrotropin-stimulated serum thyroglobulin measurement predicts differentiated thyroid carcinoma metastases three to five years later. J Clin Endocrinol Metab 90: 5047-5057, 2005.

9. American Cancer Society. http://www.cancer.org. Accessed May 3, 2006.

10. Hundall SA, Fleming ID, Fremgen AM, Menck HR. 1998 A National Cancer Database report on 53,856 cases of thyroid carcinoma treated in the U.S., 1985-1995.

11. American Thyroid Association Guidelines Taskforce. Management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 16 (2): 109-141, 2006.

12. Cavalieri RR, McDougall IR. In vivo isotopic tests and imaging. In: Braverman LE, Utiger RE, eds. Werner and Ingbar’s The Thyroid: A Fundamental and Clinical Text. 7th ed. Philadelphia, Pa: Lippincott-Raven Publishers; 1996:119-143.

13. Maini CL, Sciuto R, Tofani A. Delayed thyroid-stimulating hormone suppression by L-thyroxine in the management of differentiated thyroid carcinoma. Eur J Cancer. 1993;29:2072-2073.

14. Botella Carretaro

15. Rosário PW, Fagundes TA, Rezende LL, et al. Assessing hypothyroidism in the preparation of patients with thyroid cancer. The Endocrinologist 2006;16:25-29.

16. Luster M, Felbinger R, Dietlein M, Reiners C. Thyroid hormone withdrawal in patients with differentiated thyroid carcinoma: a one hundred thirty-two patients pilot survey on consequences of hypothyroidism and a pharmacoeconomic comparison to recombinant thyrotropin administration. Thyroid 2005;15(10):1147-1155.