Differentiated thyroid cancer

The Natural Thyroid Diet

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Management is similar for all cases and commences with radical thyroidectomy preserving parathyroid and recurrent laryngeal nerve function. Low risk patients (those with small intrathyroidal papillary or micro-angioinvasive/minimally invasive follicular tumours) are sometimes managed by thyroid lobectomy but most clinicians prefer the radical approach for all patients. Radioiodine therapy (40-80 mCi = 1500-3000 MBq) to ablate the thyroid remnant follows the operation. This rids the body of all iodine avid normal thyroid, obviating the risk of future second tumours (papillary) and rendering the subsequent screening programme (both thyroglobulin and radioio-dine) more sensitive and specific for detecting relapse. External beam radiotherapy is delivered to the neck where the tumour was locally invasive at operation (giving a dose of 5000 cGy in 5 weeks via a well executed, CT planned, three field MV photon plan in a shelled patient, the volume being parallel to a straight cervical spine).

If the patient presents with metastatic disease, or at relapse after partial thyroidectomy, radical thyroidectomy and ablation is still required because optimal management is based on the ability of most differentiated cancers to concentrate radioiodine (I131)—albeit usually less avidly than the parent gland. A carefully conducted radioiodine programme can prolong life substantially in many of these patients and achieve complete and durable response in a significant number— small bulk relapse and high iodine avidity being better response predictors.

Following radical thyroidectomy and radioiodine ablation of the stump, the patient has serial clinical examinations with at least two whole body radioiodine whole body profile scans in the next 1V2 years (each performed after 3 months off thyroxine, 8 days off liothyronine and the tracer dose being given when the TSH is known to be above 30 Uu/L or after 200 |ig of TRH iv—hereafter referred to as 'optimal conditions for radioiodine'). Serum thyroglobulin is measured at each clinical consultation and this important serum marker is more sensitive for relapse under the optimal conditions just described, although worthwhile when the patient is on thyroid replacement. If two iodine scans over the first 1.5 years are negative, and the clinical examination and thyroglobulin are negative, then iodine scanning is only used in suspected relapse (and even then many would go straight to an iodine therapy dose with a whole body scan on the 'tail-end' of the dose, because of the possibility of a tracer dose scan missing low avidity, but therapeutically relevant, uptake).

Papillary cancer tends to relapse first in neck nodes (and then mediastinal nodes) before the lungs and then bones. The treatment of neck nodal disease is surgical resection (preceded by an iodine profile scan under optimal conditions) followed by radiodine therapy where appropriate. Pre-operative imaging to define the extent of the nodal disease should be with MRI and not CT, because of the iodine load with CT contrast agents.

Metastatic disease further afield is treated by serial doses of radio-iodine (150 mCi = 5500 MBq), using the whole body scans after each dose and the serial thyroglobulin estimation to guide progress, as well as other imaging. Iodine therapy is continued at 4-6 monthly intervals until maximal remission, so long as the FBC and creatinine are satisfactory; care is needed after a cumulative dose of 1 Ci.

In patients who do not relapse, physical examination (with careful attention to the neck and CXR) and blood checks to ensure TSH suppression and minimal serum thyroglobulin readings (<2 ^g/L) constitute follow-up, the periodicity of which decreases with the passage of time; remember that this disease can relapse up to 15 years from diagnosis.

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