Management of low-risk differentiated thyroid cancer

To summarize the definitions of and management recommendations for low-risk thyroid cancer made by the American and European Thyroid Associations and synthesize this information with the recent literature, including systematic evaluations of tumor staging systems guiding therapy.

The American Thyroid Association and European Thyroid Association guidelines were compared and pertinent literature since 2005 was reviewed.

Of papillary thyroid microcarcinomas (PTMC), up to 50% breach the thyroid capsule, 64% have lymph node metastases, up to 43% are multifocal, and as many as 2.8% have distant metastases. Locoregional and distant recurrences are, respectively, as high as 5.9% and 1.5%. As many as 1 in 4 patients with a papillary thyroid carcinoma 1.5 cm or smaller develop persistent disease. Cancer-related mortality rates are usually less than 1%, but are as high as 2% in some reports. Tumor staging systems are too inaccurate to guide therapy.

It is unlikely that many patients will forgo treatment after understanding their risk, especially when total thyroidectomy and radioiodine (131I) therapy can reduce the PTMC recurrence or persistence disease rate to zero. Preoperatively diagnosed PTMC should be treated with total or near-total thyroidectomy, regardless of tumor size. For very low-risk patients with unifocal PTMC smaller than 1 cm that is removed by chance during surgery to treat benign thyroid disease, lobectomy alone without 131I therapy may be sufficient therapy if there are no concerning histologic features and no tumor extension beyond the thyroid, metastases, history of head and neck irradiation, or positive family history--any of which requires total or near-total thyroidectomy and remnant ablation with 30 mCi.