Thyroid Cancer: Extent of Thyroidectomy
Thyroid Cancer: Extent of Thyroidectomy
An understanding of the risk groups in differentiated thyroid cancer is necessary before the extent of thyroidectomy can be discussed. Our knowledge of the prognostic factors comes from univariate and multivariate analysis of various prognostic factors that have been studied over the past two to three decades. The initial study came from the European Organization for Research and Treatment of Cancer (EORTC) Thyroid Cancer Cooperative Group in 1979. Similar studies were performed in the United States at the Mayo Clinic (Minn), the Lahey Clinic (Mass), University of Chicago (Ill), and Memorial Sloan-Kettering Cancer Center (NY). The major prognostic factors in all of these studies were patient age, tumor grade, distant metastasis, tumor size, and extrathyroidal extension. The prognostic factors in differentiated thyroid cancer are well described by Dean and Hay elsewhere in this issue. (pp 229-239) Similarly, they report the most important prognostic factors in the evaluation of patients with thyroid cancer as patient age, tumor grade, distant metastasis, extrathyroidal invasion, tumor size, and completeness of resection. Based on their low- and high-risk groups, survival is excellent in the low-risk group, while the disease can frequently be fatal in the high-risk group.
Investigators at the Memorial Sloan-Kettering Cancer Center 6 divided the prognostic factors based on patient-related and tumor-related factors. Patients were divided into groups according to low, intermediate, or high risk. The low-risk group consisted of low-risk patients (under the age of 45) with low-risk tumor, and the high-risk group consisted of high-risk patients (above the age of 45) with high-risk tumor. The intermediate-risk group consisted of two categories: low-risk patients (under the age of 45) with high-risk tumor or high-risk patients (above the age of 45) with low-risk tumor. Based on these separate risk-group categories, investigators were able to show significant statistical differences in the survival rate. Long-term survival was 99% in the low-risk group, 87% in the intermediate-risk group, and 57% in the high-risk group.
It is clear from these risk groups that the discussion regarding the extent of thyroidectomy should be based primarily on the risk-group analysis of the patient in the operating room. In the low-risk group, where radioactive iodine treatment is generally not necessary, the removal of all gross disease most probably with lobectomy is satisfactory, while in the high-risk group, total thyroidectomy is indicated to facilitate RAI therapy. In the intermediate-risk group, decisions regarding the extent of thyroidectomy should be based mainly on tumor-related factors. For example, for high-risk tumor, where RAI therapy may be necessary post-operatively, a total thyroidectomy should be considered. The presence or absence of poorly differentiated carcinoma is important since these patients have more aggressive tumors, a higher chance of local recurrence, and a strong consideration for RAI and external radiation therapy. A large number of patients with poorly differentiated carcinoma do not take up RAI. Various other prognostic factors (eg, DNA ploidy, adenylate cyclase response, epidermal growth factor receptor, cathepsin, and telomerase) are analyzed in the evaluation of thyroid cancer. We will learn more about these biological prognostic factors in the future through molecular biology in thyroid cancer. Comparative genomic hybridization has been utilized in 60 patients with differentiated thyroid cancer. To clarify the role of thyroidectomy and postoperative radiation, the American College of Surgeons Oncology Group is considering instituting randomized, prospective trials to evaluate the extent of surgery and postoperative radiation. Nevertheless, with currently available information, patients can be placed in low-, intermediate-, high-risk groups (Fig 1) with long-term survival rates of 99%, 87%, and 57%, respectively. These risk groups affect the decision of optimal type of surgical resection.
(Enlarge Image)
Long-term survival of patients with differentiated thyroid cancer, according to risk group (based on a review of Memorial Sloan-Kettering Cancer Center thyroid data base, 1,038 patients). The separate risk categories (low, intermediate, and high) show a significant statistical difference in long-term survival.
An understanding of the risk groups in differentiated thyroid cancer is necessary before the extent of thyroidectomy can be discussed. Our knowledge of the prognostic factors comes from univariate and multivariate analysis of various prognostic factors that have been studied over the past two to three decades. The initial study came from the European Organization for Research and Treatment of Cancer (EORTC) Thyroid Cancer Cooperative Group in 1979. Similar studies were performed in the United States at the Mayo Clinic (Minn), the Lahey Clinic (Mass), University of Chicago (Ill), and Memorial Sloan-Kettering Cancer Center (NY). The major prognostic factors in all of these studies were patient age, tumor grade, distant metastasis, tumor size, and extrathyroidal extension. The prognostic factors in differentiated thyroid cancer are well described by Dean and Hay elsewhere in this issue. (pp 229-239) Similarly, they report the most important prognostic factors in the evaluation of patients with thyroid cancer as patient age, tumor grade, distant metastasis, extrathyroidal invasion, tumor size, and completeness of resection. Based on their low- and high-risk groups, survival is excellent in the low-risk group, while the disease can frequently be fatal in the high-risk group.
Investigators at the Memorial Sloan-Kettering Cancer Center 6 divided the prognostic factors based on patient-related and tumor-related factors. Patients were divided into groups according to low, intermediate, or high risk. The low-risk group consisted of low-risk patients (under the age of 45) with low-risk tumor, and the high-risk group consisted of high-risk patients (above the age of 45) with high-risk tumor. The intermediate-risk group consisted of two categories: low-risk patients (under the age of 45) with high-risk tumor or high-risk patients (above the age of 45) with low-risk tumor. Based on these separate risk-group categories, investigators were able to show significant statistical differences in the survival rate. Long-term survival was 99% in the low-risk group, 87% in the intermediate-risk group, and 57% in the high-risk group.
It is clear from these risk groups that the discussion regarding the extent of thyroidectomy should be based primarily on the risk-group analysis of the patient in the operating room. In the low-risk group, where radioactive iodine treatment is generally not necessary, the removal of all gross disease most probably with lobectomy is satisfactory, while in the high-risk group, total thyroidectomy is indicated to facilitate RAI therapy. In the intermediate-risk group, decisions regarding the extent of thyroidectomy should be based mainly on tumor-related factors. For example, for high-risk tumor, where RAI therapy may be necessary post-operatively, a total thyroidectomy should be considered. The presence or absence of poorly differentiated carcinoma is important since these patients have more aggressive tumors, a higher chance of local recurrence, and a strong consideration for RAI and external radiation therapy. A large number of patients with poorly differentiated carcinoma do not take up RAI. Various other prognostic factors (eg, DNA ploidy, adenylate cyclase response, epidermal growth factor receptor, cathepsin, and telomerase) are analyzed in the evaluation of thyroid cancer. We will learn more about these biological prognostic factors in the future through molecular biology in thyroid cancer. Comparative genomic hybridization has been utilized in 60 patients with differentiated thyroid cancer. To clarify the role of thyroidectomy and postoperative radiation, the American College of Surgeons Oncology Group is considering instituting randomized, prospective trials to evaluate the extent of surgery and postoperative radiation. Nevertheless, with currently available information, patients can be placed in low-, intermediate-, high-risk groups (Fig 1) with long-term survival rates of 99%, 87%, and 57%, respectively. These risk groups affect the decision of optimal type of surgical resection.
(Enlarge Image)
Long-term survival of patients with differentiated thyroid cancer, according to risk group (based on a review of Memorial Sloan-Kettering Cancer Center thyroid data base, 1,038 patients). The separate risk categories (low, intermediate, and high) show a significant statistical difference in long-term survival.
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