Relapse Rates and the Extent of Initial Thyroid Surgery

Thyroid Factor

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Recurrence rates are high with large thyroid gland remnants. Some find that patients treated by lobectomy alone have a 5% to 10% recurrence rate in the opposite thyroid lobe [16,29] and an overall long-term recurrence rate over 30% (versus 1% after total thyroidectomy and 131I therapy [3]) and the highest frequency (11%) of subsequent pulmonary metastases [30]. Higher recurrence rates are also observed with cervical lymph node metastases and multicentric tumors, which also provide justification for more complete initial thyroid resection [3].

In one study from the Mayo Clinic [31] of patients with papillary carcinoma, tumor recurrence rates during the first 2 years after surgery were about fourfold greater after unilateral lobectomy than after total or near-total thy-roidectomy (26% versus 6%, P = 0.01). In a subsequent report from the same institution, patients with papillary carcinoma whose AGES score was 4 or more had a 25-year cancer mortality rate almost twice as high after lobectomy than after bilateral thyroid resection (65% versus 35%, P = 0.06) [18]. In a study of AMES low risk patients from the same institution, 20-year rates for local recurrence and nodal metastases were, respectively, 14% and 19% after unilateral lobectomy, and 2% and 6% after bilateral lobar resection (P = 0.001), leading the authors to conclude that bilateral lobar resection represents the preferable initial surgical approach to patients with low risk papillary thyroid carcinoma [19]. In another study of patients with papillary carcinoma [15], near-total thyroidectomy decreased the risk of death from tumors larger than 1 cm and decreased the risk of recurrence as compared with lobectomy or bilateral subtotal thyroidectomy.

We found recurrence and cancer death rates were both about 50% lower after near-total or total thyroidectomy as compared with less surgery in patients with stage II and III tumors

(Figures 12.2 and 12.3) [3], and that surgery more extensive than lobectomy was an independent variable that by multivariate analysis reduced the mortality rate of thyroid carcinoma by 50%. Moreover, the differences in outcome between total thyroidectomy and lobectomy cannot be resolved by 131I therapy (Figure 12.1). Thus, there is abundant evidence that microscopic residual disease remaining after initial surgery leads to high recurrence and carcinoma mortality rates.

Current Guidelines for Surgery

Current guidelines on the treatment of DTC from the USA [32] and Europe [33] advise total or near-total thyroidectomy followed by 131I ablation of the thyroid remnant for most patients.Although the treatment of children has been more controversial, many now recommend that they be treated the same as adults [22]. Thus, when the diagnosis of thyroid cancer is known preoperatively total or near-total thyroidectomy should be done for nearly all patients [34] because it improves disease-free survival, even in children and adults with low risk tumors [19,35-37]. Lobectomy alone is adequate surgery for papillary micro carcinomas provided the patient has not been exposed to radiation and has no other risk factors, including a familial predisposition to the tumor, and the papillary carcinoma is smaller than 1 cm

Mazzeferri Thyroid Cancer
Figure 12.2 Tumor recurrence after subtotal or total thyroidectomy (see Figure 12.1 legend for explanation of surgery). (Drawn from the data of Mazzaferri and Kloos [2].)
Subtotal Thyroidectomy Images
Figure 12.3 Cancer-specific mortality after subtotal or total thyroidectomy (see Figure 12.1 legend for explanation of surgery). (Drawn from the data of Mazzaferri and Kloos [2].)

and is unifocal and confined to the thyroid without vascular invasion (see Chapter 29) [3,38,39]. The same is true for minimally invasive follicular cancers smaller than about 2 cm. A large thyroid remnant, however, hampers follow-up with serum Tg determinations and whole-body 131I scans and the decision to forgo complete thyroidectomy should be made in consultation with the patient, who must be informed of the difficulty in follow-up when lobectomy alone is performed.

Thyroglossal Duct Cyst Carcinomas

Small papillary carcinomas that arise in a thy-roglossal duct remnant are typically encapsu lated by the cyst and usually are not recognized until the permanent histological sections are reviewed [40]. When the clinical diagnosis of a thyroglossal duct cyst is made, the workup should include an ultrasound examination and fine-needle aspiration cytology in order to plan the correct surgery for a possible carcinoma [41]. Dissection of the tract and removal of the hyoid bone (Sistrunk operation) is adequate for most patients because these tumors rarely metastasize [42]. However, one study found a high incidence of intrathyroidal carcinomas in such cases, some with aggressive behavior, suggesting that total thyroidectomy may be justified [43]. Treatment must be tempered by the patient's age and the size and extent of the tumor [44]. It is difficult to justify anything more than a Sistrunk procedure for a young person with a small (<1cm) tumor confined to a thyroglossal cyst and an ultrasonographically normal thyroid. On the other hand, with older patients and those with invasive or metastatic tumor or histological features that portend a poor prognosis, or following head and neck irradiation, or with a malignant tumor in the thyroid gland, the more classic approach of total thyroidectomy and 131I therapy seems warranted [44].

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