Therapy and Prediction of Recurrence in Thyroid Cancer
Consequently, the general survival rate of patients with DTC is very high provided treatment is instituted early. The population of survivors has changed due mainly to an earlier primary treatment, and thus strategies presented in the past based on the majority of patients with advanced disease do not apply anymore. Patients are at different risk of recurrence depending on prognostic factors such as age, sex, size of the tumour, stage and histological type. Considering that one-third of recurrences occur after the first decade, and up to 30-40 years after initial apparently successful therapy, and the recurrence/metastases are most often treatable by ¹³¹I, a careful follow-up of these patients is pertinent Much controversy surrounds the matter of surgical treatment (see Table 1), most often, though, performed as total thyroidectomy with or without ablation of the remnant with ¹³¹I. A more conservative surgica approach (lobectomy+isthmusectomy) has been advocated by some for DTC patients at low risk and with a good a priori prognosis, in particular in patients with papillary microcarcinoma (<1cm) and small (<4cm) minimally invasive follicular thyroid cancers.

Such conservative therapy may, however, have an implication for the efficiency of the follow-up and should be discussed with the patient.^1-3,7-9 Equally controversial is the treatment with levothyroxine (L-thyroxne) after surgery with or without ablation. In the past, when TSH measurements were not sufficiently sensitive to distinguish those with hyperthyroidism from those without, the strategy was to suppress TSH to undetectable levels in order to avoid any growth promotion of remaining cancerous cells. This must, however, be considered an obsolete approach with the development of TSH methods able to discriminate hyperthyroid patients from norma controls, and since it has never been proved that complete suppression of TSH is necessary for a favourable survival in patients with low-risk DTC. On the contrary, data from a National Thyroid Cancer Treatment Co-operative Study in the US did not support the concept that suppressing TSH to undetectable, thyrotoxic ranges was required to prevent disease progression. There is an increasing awareness of possible long-term damaging effects - in terms of cardiac arrythmias, cardiovascular deaths and osteoporosis - if survivors are treated life-long to a mild to moderate hyperthyroidism; this is particularly important in post-menopausal women As a practical matter, the most appropriate L-thyroxine dose is that which reduces the serum TSH to just below the lower limit of the normal range for the assay being used (typically 0.1-0.4 mU/l).⁶