Rationale and Indications for Hemithyroidectomy

Before 1945, thyroid cancers were more aggressive tumors in most other parts of the world except Japan. This is probably because in Japan there was high iodine intake as a result of the consumption of seaweed and seafood. In the United States, the addition of iodine to table salt, bread, and water was begun in the 1920s and 1930s, and in European countries it was added after the end of World War II. Currently, most of the Western countries have become iodine sufficient, and some even iodine rich, such as the United States. Whereas the biologic characteristics of thyroid cancers have remained virtually unchanged in Japan, there have been considerable changes in clinical and survival patterns in patients with thyroid cancers in the United States.2646 In iodine-rich areas, approximately 90% of all differentiated thyroid cancers of follicular cell origin are papillary thyroid carcinomas, and of these, approximately 90% are low-risk cancers.20

Using Cady's AMES scoring system, it is usually easy to determine whether a patient should be included in a low-risk or a high-risk category at the time of initial operation.1 Hay and associates47 in 1993 proposed a new prognostic scoring system, MACIS (metastases, age, completeness of resection, invasion, and size), which is applicable at the time of surgery by excluding histologic grade from the previous AGES classification system.

The introduction of fine-needle aspiration biopsy has greatly facilitated the accurate preoperative diagnosis of papillary thyroid carcinoma. Therefore, surgeons should usually be able to determine whether a patient is at high or low risk at the time of the initial surgery based on either AMES, MACIS, or any other classifying system. Since this high- or low-risk information is 97% to 99% accurate, it should be useful in selecting the extent of thyroidectomy that will result in the best prognosis with the least risk of complications.

TABLE 11-4. Results in Patients with Low-Risk Papillary Thyroid Carcinoma at Tokyo Women's Medical University Hospital, 1981-1989*

Tumor Recurrence

Type of

No. of

No. of Cancer

remnant

lymph

distant

Surgery

Patients

Deaths

thyroid

local

node

metastasis

Total Thyroidectomy

MND performed*

57

0

0

0

8

5

MND not performed

2

0

0

0

1

0

Hemithyroidectomy

MND performed

296

2

2

6

23

10

MND not performed

47

0

0

0

0

0

Partial Lobectomy

5

0

0

0

1

0

Total

408

2

2

6

33

15

•Mean follow-up time was 12 years. MND = modified neck dissection.

•Mean follow-up time was 12 years. MND = modified neck dissection.

TABLE 11-5. Postoperative Survival Rates in Patients Who Underwent Surgery at Tokyo Women's Medical University Hospital, 1981-1989

Survival Rates {%)

5 years 10 Years J5 Years

Risk No. of

Group Patients overall disease-free overall disease-free overall disease-free

Low 408 100 95 99 92 99 88

High 36 91 36 64 30 54 8

Hemithyroidectomy should be performed for low-risk papillary thyroid carcinoma that is macroscopically localized to one lobe to decrease the risk of local recurrence. We believe that even when a patient is in the low-risk papillary thyroid carcinoma group, total thyroidectomy or near-total thyroidectomy is preferable to hemithyroidectomy when the patient has (1) multicentric occurrence of cancer in both lobes or (2) markedly invasive cancer in both lobes, including the diffuse sclerosing variant of papillary carcinoma that occurs in young individuals.48

Whether these cancers can be diagnosed at the time of hemithyroidectomy is controversial. Using preoperative or intraoperative ultrasonography and careful palpation of the thyroid gland, experienced surgeons can usually know at the time of operation whether there is significant bilateral involvement. Lesions as small as 2 mm can be detected in the otherwise normal thyroid tissue by these methods. In Japan, preoperative ultrasonography has been widely used in many institutions.

After a hemithyroidectomy is carried out, the resected thyroid specimen is longitudinally cut on the operating table as a routine procedure and the cut surface is macroscopically examined. Hemithyroidectomy is usually indicated when papillary thyroid carcinoma on the cut surface shows a well-circumscribed lesion without any associated satellite lesions (Fig. 11-1 A) or with a small number of minute

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FIGURE 11-1. Macroscopic views of the cut surfaces of surgical specimens obtained by hemithyroidectomy (A, B) or total thyroidectomy (C), showing various modes of intrathyroid papillary cancer spread. A, A sharply marginated primary lesion, measuring 3x2 cm, is located in the left thyroid lobe and accompanied by four proven metastatic jugular chain nodes and one peritracheal node. The patient is a 43-year-old woman who is currently alive, well, and euthyroid without thyroid-stimulating hormone (TSH) suppression 10 years postoperatively. B, A 3 x 2-cm lesion was found in the right lobe with intrathyroid satellite lesions (arrowheads) associated with proved metastatic lesions in two jugular nodes and one peritracheal node. The patient was a 43-year-old woman who is alive, well, and euthyroid without TSH suppression 9 years after surgery. C, A diffusely infiltrating, whitish papillary carcinoma was found in the right lobe, and many tiny intrathyroid metastatic foci were found in the left lobe. Miliary lung metastases were noted on a chest radiograph at the time of operation. Total thyroidectomy and bilateral neck dissection followed by ,3II therapy were performed on the patient, a 30-year-old woman who is alive with disease 9 years after surgery, under TSH suppression therapy.

lesions only in areas close to the main lesion (Fig. 11-1B), and the contralateral lobe is normal to palpation. Intrathyroidal deposits of cancer are seen as whitish spots. When we have observed that papillary thyroid cancer tissue is known preoperatively to contain psammoma bodies, as in the case of the diffuse sclerosing variant, psammomatous shadows on a soft tissue roentgenogram of a resected specimen indicate intrathyroidal cancer spread.48 When intrathyroidal metastatic lesions are in close proximity to the surgical margin (Fig. 11-2), the remaining contralateral lobe should be removed.

Previously, we occasionally failed to detect pulmonary metastases in young patients with papillary thyroid carcinoma because of normal chest radiographs at the time of the initial operation. Those patients subsequently experienced miliary lung metastases. They usually have diffusely invasive growth of cancer in the thyroid gland (see Fig. 11- 1C) and often have multiple lymph node metastases. Today, we recommend preoperative computed tomography scanning of the chest in such patients to detect lung metastases preoperatively. Those patients are then classified as high risk and are treated by total thyroidectomy. In our follow-up study, we also noted the postoperative development of lung metastasis in elderly patients, most of whom had a large primary tumor at the initial surgery. This result indicates the importance of tumor size as one of the criteria for classifying a high-risk patient who is elderly. Because of these observations, we currently perform more total thyroidectomies than in the past, although most lung metastases in elderly patients did not actually take up radioiodine.

In our series at the Tokyo Women's Medical University Hospital, 408 patients with low-risk papillary thyroid carcinoma were treated from 1981 through 1989, a total thyroidectomy was done in 60 (15%), hemithyroid-ectomy including partial resection of the contralateral lobe in 343 (84%), and partial lobectomy in 5 (1%) (see Table 11-3). An average 12-year follow-up study in these patients was completed through August 15, 2002, and these results are shown in Table 11 -4. Of the 343 hemithy-roidectomy patients, only 2 patients (0.5%) died of thyroid cancer. Two patients (0.5%) had recurrence in the remaining contralateral thyroid lobe. Local recurrence in the thyroidectomy bed and at the scar of open biopsy carried out elsewhere occurred in 5 patients and 1 patient, respectively. Cancer recurrence in lymph nodes was noted in a total of 31 patients (8.8%) who had undergone modified radical neck dissection and in 2 who had not undergone neck lymph node dissection. Lung metastasis was detected in 15 patients: 5 (8.5%) of 59 patients who had total thyroidectomy and 10 (2.9%) of 343 patients who had hemithyroidectomy. All 5 patients who had total thyroidectomy failed to have radioiodine uptake in the lung metastases. The 4 patients treated with hemithyroidectomy underwent completion total thyroidectomy, and only 1 of them was successfully treated with 131I. The other 3 patients did not have radioiodine uptake in the lung metastases. In the remaining 6 patients, a completion total thyroidectomy was not performed because of the patients' age, associated diseases, and/or concomitant recurrences.

FIGURE 11-2. Soft tissue roentgenogram of a thyroid specimen resected by subtotal thyroidectomy in a female patient with the diffuse sclerosing variant of papillary carcinoma. Note the presence of many psammomatous calcifications throughout the whole specimen, including the surgical cut end (arrow), which definitely indicates cancer remaining in the rest of the thyroid lobe.

FIGURE 11-2. Soft tissue roentgenogram of a thyroid specimen resected by subtotal thyroidectomy in a female patient with the diffuse sclerosing variant of papillary carcinoma. Note the presence of many psammomatous calcifications throughout the whole specimen, including the surgical cut end (arrow), which definitely indicates cancer remaining in the rest of the thyroid lobe.

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