More than 90% of thyroid cancers are differentiated thyroid carcinoma (DTC), including papillary and follicular carcinomas, which are less malignant, usually do not spread rapidly and do not metastasize, and often have a good outcome with surgical resection.
Total thyroidectomy versus partial thyroidectomy (lobectomy) is currently the common clinical procedure. Which is the better procedure for low-risk patients? A recent study summarizes and discusses this.
Thyroid cancer risk stratification
Let’s look at the risk stratification of thyroid cancer and see who the “low-risk” DTC patients in this study are.
The outcome of thyroid cancer is related to a number of factors, such as age, tumor size, and presence of metastases. There are several risk stratification schemes in the profession based on these factors. Among them, Memorial Sloan-Kettering Cancer Center (USA) has proposed the GAMES scheme, which divides both patients and tumors into two groups: high risk and low risk, which are then combined and judged (Table 1).
Table 1: GAMES protocol
|
Risk grouping |
Patient factors |
Primary thyroid tumor factors |
|
Low risk |
|
Tumor <4 cm, no extrathyroidal invasion; papillary carcinoma; no metastasis |
|
High risk |
> Age 45 |
Tumor > 4 cm with extrathyroidal invasion; follicular carcinoma; metastasis |
|
High risk cases |
High-risk patients + high-risk tumors |
|
|
Moderate risk cases |
Low-risk patients + high-risk tumors; high-risk patients + low-risk tumors |
|
|
Low-risk cases |
Low-risk patients + low-risk tumors |
|
What is the difference between a total and partial thyroidectomy?
For thyroid cancer confined to one side of the gland, some authors advocate total thyroidectomy.
The advantages of this procedure are 1) complete resection, which reduces the rate of local and contralateral recurrence, and 2) facilitates postoperative detection of cancer recurrence and metastasis by thyroid radionuclide scanning and thyroglobulin (Tg) testing.
But the risk of complications is higher with total resection compared with partial resection: the incidence of postoperative hypoparathyroidism and laryngeal recurrent nerve injury is 4.9% and 5.9%, respectively, compared with 0.8% and 2.0% with partial resection. This is the cause of concern for some experts.
Partial resection (lobe plus isthmus) has also been advocated. This procedure can be used in some low-risk patients: 1) with microscopic papillary carcinoma less than 1 cm in diameter and no cervical lymph nodes or distant metastases; and 2) without suspicious nodes on preoperative ultrasound or intraoperative contralateral exploration.
It is advantageous because 1) the incidence of hypoparathyroidism and recurrent laryngeal nerve palsy is significantly lower than with total resection; 2) long-term survival is not lower than with total resection when partial resection is done in appropriately selected low-risk cases; and 3) if postoperative contralateral recurrence occurs, second-stage total thyroidectomy is easier, patient long-term survival is not compromised, and the safety of second-stage total resection is the same as that of first-stage lobectomy plus isthmus.
Total versus partial thyroidectomy, what is the choice?
Take the most common form of papillary carcinoma as an example. A study that included 52,173 patients (43,227 total thyroidectomies and 8,946 partial resections) showed no significant difference in the effect of the two procedures on disease recurrence or survival for tumors smaller than 1 cm, and a higher risk of recurrence and death with partial resection for tumors larger than 1 cm. However, it has also been shown that there is no significant difference in 20-year survival after the two procedures for papillary carcinomas with tumor sizes of 1 to 4 cm.
Currently, the American Thyroid Association (ATA) recommends both bilateral resection (subtotal or total) and unilateral resection for thyroid cancers between 1 and 4 cm in size, without extraglandular metastases or lymph node metastases, where the extent of glandular resection has little impact on survival and where remedial treatment after unilateral lobectomy is effective. However, in patients older than 45 years with contralateral thyroid nodules, history of head and neck radiation therapy, and familial DTC, total thyroidectomy is recommended.
Because DTC is well nodulated, it is important to strive for improved outcomes and to minimize adverse effects of treatment. The specific surgical option needed for thyroid cancer treatment will be determined by the surgeon after multiple assessments.