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It is generally agreed that the minimal operation to be performed in a
patient with a thyroid nodule suspected of malignancy should be an ipsilateral
lobectomy with isthmusectomy. By using this approach one would less frequently
have to re-operate on the same side in case an initial benign diagnosis
by fine needle aspiration or peroperative frozen section should be changed
by the pathologist to a malignant one. A re-operation on the same side
substantially increases the risk of complications such as damage to the
parathyroid glands or the recurrent laryngeal nerve. It also makes the
probability of removing all thyroid tumour tissue much more likely.
There is still much controversy as to the recommended extent of a definite operation i.e. whether to perform a total thyroidectomy in all cases if malignancy is established or to leave the remaining thyroid lobe in the patient with a small encapsulated papillary thyroid carcinoma. No prospective studies exist to clarify this. However, the most prevailing view is that coincidentally removed small papillary carcinomas (less than 1 cm) sometimes in a gland with Graves' disease would not require further surgery, but all other thyroid cancers should have a near total thyroidectomy performed when it can be done safely. The remaining thyroid cells should be ablated by I-131. There are obvious advantages of a total thyroidectomy rather than a more limited operation in relation to the post-therapy follow-up procedures (Table 3). The survival and the recurrence rates of both papillary and follicular thyroid carcinomas have been shown to be dependent on the extent of surgery and postoperative I-l3 therapy(2,l0). If the patient has had a near total thyroidectomy with remaining I-131 ablation it is quite obvious that this patient needs treatment with thyroid hormone (levothyroxine). It is, however, much more controversial if such a patient or a patient with a thyroid remnant should be treated with levothyroxine to obtain a TSH within normal reference limits of a 2nd or 3rd generation assay(ll), or if these patients should be treated with suppressive doses. Thyroid carcinomas have been shown to possess TSH receptors and to respond to TSH by the production of adenylate cyclase(l 12). It is also anticipated that thyroid carcinomas might grow under the influence of TSH(13). On the other hand, the growth of thyroid carcinoma cells seems to be unrelated to the normal physiological regulatory influence of TSH(13). Table 3: Advantages of total thyroidectomy in the follow-up of differentiated thyroid carcinoma
Clinical studies have demonstrated an increased survival rate and a decreased recurrence rate when thyroid carcinoma patients were treated with levothyroxine(2 12, 13ff 14), but these studies have mainly been performed when less sensitive TSH assays were employed. It has since been much debated whether rendering the patients subclinically hyperthyroid might increase their risk for adverse effects to the heart or decalcification of the bones(l2). Since no good evidence exists concerning the beneficial effects over the less favourable ones it is recommended that long-term controlled clinical trials be performed concerning the positive effect of treating patients with high doses of levothyroxine compared to the effect of treating the patient to a euthyroid state i.e. with TSH within the normal range. Until then it is advisable to use fully suppressive doses of levothyroxine obtaining a low TSH by a 2nd or 3rd generation assay(ll l2,l3,l4,l5). The treatment of medullary thyroid carcinoma should always be a total thyroidectomy. When this type of cancer is clinically evident it has a very poor prognosis, since spead has already occurred. The strategy thus aims at an early diagnosis, which is possible for the familial type by screening of family members for mutations in the RET oncogene and treatment as early as possible. It is still debated at which age children should be thyroidectomised if a mutation is found(7). Anaplastic carcinomas are very aggressive rapidly growing tumours that can only be palliated. External radiation and chemotherapy has little if no effect and should only be used in trials. Also very advanced stages of differentiated thyroid carcinomas have a poor prognosis. I-131 therapy may be useful and in few cases local external radiation or chemotherapy may also have an effect, most often not curable. Octreotide - a long-acting somatostatin analogue that inhibits cell growth and hormone secretion - has recently been tried in advanced thyroid cancer without success(l6). Localised metastases in the lung or bones can in selected cases be operated. |
