The follow-up of patients with papillary or follicular cancer should be appropriate for the stage and extent of the disease. Occult foci (nonpalpable lesions, <1 cm) of papillary cancer that are discovered at the time of a lobectomy for benign thyroid disease may not require additional therapy or testing. Most endocrinologists agree that suppression of thyrotropin is appropriate for all patients with clinically important well-differentiated thyroid cancer. The degree of suppression should be individualized to avoid complications of subclinical hyperthyroidism. Serum Tg levels should be followed up in all patients.
Many endocrinologists suggest that Tg and sensitive thyrotropin measurements should be obtained every 6 months for the first 3 years after initial therapy, and then yearly thereafter. Some clinicians withdraw thyroid hormone therapy annually for 1 to 3 years for radioactive iodine scanning, especially for patients with high-risk cancer.[7] If residual or recurrent disease is detected, radioiodine therapy is administered. Other investigators withdraw thyroid hormone annually for the purpose of measuring Tg levels, and determine the need for a scan based on the Tg result. Most endocrinologists individualize the frequency of repeated radioiodine scans, and do repetitive scanning only for those patients with aggressive disease or elevated or rising serum Tg levels. The anticipated availability of recombinant human thyrotropin to stimulate both radioactive iodine uptake for scanning and Tg measurements may alter these practice patterns. Chest radiographs may be obtained periodically, with the frequency dependent on the individual clinical situation. Bone pain should be evaluated initially with appropriate radiographs, since bone scans may be normal despite bony metastases. Some endocrinologists obtain periodic neck ultrasound examinations, particularly in patients with previous locally invasive disease and in patients who have had a lobectomy as their only surgical procedure, because radioiodine scanning is not possible. In patients with elevated or rising Tg levels and normal radioiodine scans, repeated scanning may be indicated after a therapeutic dose of radioiodine. If scans are normal and the serum Tg level is high, ultrasonography of the neck, as well as appropriate computed tomography scans or magnetic resonance imaging, may be indicated. Evaluation of the skeleton and central nervous system is particularly important, to avoid the consequences of undetected brain or spinal cord metastases. Other scanning agents (eg, thallium 201 or sestamibi) may be useful to search for occult metastases in selected patients.
Additional Therapies
Thyroidectomy, radioactive iodine, and levothyroxine suppressive therapy are sufficient for most patients with well-differentiated thyroid cancer. Locally recurrent disease should be resected if at all possible. When resection is not feasible, external radiation may be helpful in controlling local tumor growth, including but not limited to the neck, mediastinum, bone, spinal cord, and brain.[17] When a large mass of unresectable tumor is present and the uptake of radioiodine is limited, or when there is intractable bone pain, external beam radiation should be considered. Chemotherapy is of limited efficacy, but it may be considered in patients with symptomatic or relentlessly advancing disease.
