Background: The optimal extent of thyroidectomy for well-differentiated thyroid cancer is controversial. It has been suggested that surgeons use the Age, Metastases, Extent and Size (AMES) risk classification to decide between partial thyroidectomy (PT) or total thyroidectomy (TT).
Methods: The Surveillance, Epidemiology and End Results database was used to identify patients who underwent PT or TT for well-differentiated thyroid cancer between 1992 and 1997. Age, distant metastases, extrathyroidal extension, tumor size, AMES risk group, gender, histologic subtype, and lymph node metastases were analyzed by using logistic regression models to evaluate whether surgeons use these factors to determine extent of thyroidectomy.
Results: Of 9,226 patients, most patients had small cancers confined to the thyroid gland. Of these, 79.9% were AMES low-risk, and 83% underwent TT. Age 40 years or older (40 to 49 years: odds ratio [OR], 0.75, 95% confidence interval [CI], 0.65 to 0.86; 50 years or older: OR, 0.66; 95% CI, 0.58 to 0.75) was associated with a lower likelihood of TT, as were female gender (OR, 0.80; 95% CI, 0.70 to 0.92) and follicular histology (OR, 0.65; 95% CI, 0.55 to 0.78). Extrathyroidal extension (OR, 3.85; 95% CI, 3.09 to 4.80), regional lymph node metastases (OR, 6.98; 95% CI, 5.45 to 8.93), distant metastases (OR, 7.29; 95% CI, 2.69 to 19.8), AMES high-risk group (OR, 2.82; 95% CI, 2.36 to 3.38), and larger tumor size (OR, 1.27; 95% CI, 1.01 to 1.59) were associated with greater likelihood of TT. In multivariable analyses, only age, extrathyroidal extension, and regional and distant metastases were associated with extent of thyroidectomy; AMES risk group and tumor size were no longer significant.
Conclusions: Most patients undergo TT for well-differentiated thyroid cancer regardless of AMES risk grouping. In contrast to AMES risk-group classification, younger patients are more likely to undergo TT compared with older patients. Although extrathyroidal extension and distant metastases were associated with TT in accordance with AMES criteria, tumor size had no independent influence. Regional lymph node metastasis, not an AMES criterion, increased the likelihood of TT. Some components of AMES risk-group classification are used by surgeons to choose the extent of thyroidectomy.