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Contemporary management of papillary carcinoma of the thyroid gland

The incidence of thyroid cancer is increasing by 4% per year. Thyroid cancer has become the eighth most common malignancy diagnosed in women. Papillary cancer accounts for 80% of all thyroid cancer. The management of papillary thyroid cancer is challenging, primarily because there have been no prospective randomized trials to help guide therapeutic decision making. The purpose of this article is to discuss the contemporary management of papillary thyroid cancer, including the diagnosis and pre-operative evaluation, surgical management, postoperative thyroid hormone and radioiodine therapy, long-term follow-up, prognosis and management of recurrent and metastatic disease. The role of molecular markers to enhance the cytological diagnosis of papillary cancer and new molecular-based therapies will also be reviewed.

The therapeutic management of differentiated thyroid cancer

BACKGROUND

The management of thyroid cancer is difficult because the tumors comprise a wide range of biologic behaviors, from small papillary thyroid microcarcinomas that pose little or no threat to survival for the patient, to anaplastic thyroid cancers that are arguably the most lethal tumor. Although it may be difficult initially to determine at which end of the prognostic spectrum a patient resides, one can ordinarily estimate a patient's risk for tumor recurrence and mortality based on a triad of features as simple as the patient's age at the time of diagnosis, the tumor stage at presentation, and its initial response to therapy. While staging systems are available to assist in the management process, all are inexact and leave wide gaps in the treatment plan for a given patient. This is largely because randomized controlled trials are lacking as a result of the low incidence and generally favorable prognosis of the disease. As a practical matter, it may sometimes be difficult to reassure a patient, given the generally favorable prognosis of this group of tumors, knowing that without adequate therapy some become unexpectedly aggressive and recur years after initial management. The treatment of these tumors rests on a fine balance of providing care that reflects the anticipated course of the disease without overtreating the patient or providing reassurance that is unfounded.

OBJECTIVE

To outline the treatment strategy for patients with differentiated thyroid cancer based on the available literature and to guide clinicians through a management algorithm utilizing patient and tumor characteristics.

METHODS

This review is limited to the treatment of patients with differentiated thyroid cancer - papillary and follicular thyroid cancer - and the standard therapy required for the majority of patients.

RESULTS/CONCLUSION

The treatment of differentiated thyroid cancer requires a multidisciplinary approach, involving an experienced surgeon, radiologists and an endocrinologist. There are many unanswered questions in the management algorithm and ongoing research is needed to further define the best treatment strategy for patients with differentiated thyroid cancer.

Papillary thyroid cancer: medical management and follow-up

The incidence of epithelial derived thyroid cancer (papillary thyroid cancer and follicular thyroid cancer, known collectively as differentiated thyroid cancer) is rising. About 80% of patients with thyroid cancer have PTC and are best treated with thyroidectomy and functional lymph node dissection, followed by radioiodine ablation or therapy and performance of a posttreatment whole-body scan, followed by thyroid stimulating hormone (TSH) suppression. One year after radioiodine administration, the use of sensitive thyroglobulin (Tg) assays can separate the vast majority of patients with persistent disease from those who are free of disease and unlikely to have recurrent disease all without the need for repeat whole-body radioiodine imaging. Patients with detectable serum Tg during TSH suppression (Tg-on) or Tg that rises above 2 ng/mL after TSH stimulation (TSH-Tg) are highly likely to harbor residual tumor. TSH stimulation can be achieved using either thyroid hormone withdrawal or recombinant human TSH (rhTSH). Highly skilled screening neck ultrasonography can identify a few additional patients with subcentimeter residual neck lymph node metastases not detected by TSH-Tg. However, ultrasonography and chest computed tomography (CT) are most critical for tumor localization in those patients with Tg values that suggest residual disease or in those patients with persistent antithyroglobulin antibodies (TgAb) that falsely lower Tg measurement. TgAb quantitative titers typically resolve steadily over just a few years in patients free of disease after initial therapy. Another paradigm shift is the recognition that most patients who eventually achieve freedom from disease do so by surgery with fewer patients cured by repetitive radioiodine treatments, and even fewer cured with external beam radiation. Patients who appear to be free of disease require a lifetime of follow-up to optimize levothyroxine treatment, and they will undergo periodic stimulation testing because some will still manifest recurrent disease. Patients with persistent disease despite negative ultrasonography, chest CT, and whole-body radioiodine imaging may have a tumor identified by fluorodeoxyglucose positron emission tomography, optimally performed with combined TSH stimulation and image fusion with CT or magnetic resonance imaging. Patients with metastatic disease who are unresponsive to conventional treatment are encouraged to participate in increasingly available thyroid cancer-specific clinical trials using targeted experimental oral or intravenous chemotherapeutic agents to address this tumor that has historically proven resistant to conventional chemotherapeutic agents.