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Bryan R. Haugen, Patients with Differentiated Thyroid Carcinoma Benefit from Radioiodine Remnant Ablation, The Journal of Clinical Endocrinology & Metabolism, Volume 89, Issue 8, 1 August 2004, Pages 3665–3667, https://doi.org/10.1210/jc.2004-0920
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The initial treatment of differentiated thyroid cancer (DTC) includes surgery, radioiodine (for remnant ablation and/or therapy), and levothyroxine. Surgery and levothyroxine are generally accepted therapies, but the use of radioiodine, especially for patients with low risk for disease recurrence and mortality, remains controversial. Potential risks of radioiodine treatment include sialadenitis, xerostomia, bone marrow suppression, diminished reproductive function, and secondary malignancies. Potential benefits of radioiodine treatment include destruction of microscopic thyroid cancer, facilitation of sensitive monitoring for disease persistence or recurrence, reduction of disease-specific and overall mortality, and reduction in disease recurrence. These last two benefits on reduction of mortality and recurrence have been the topic of much debate for decades. The issue may be resolved with an appropriately designed, randomized, controlled clinical trial, but this has yet to be performed. Wong et al. (1) estimated that 1000 patients followed over 25 yr would be required to detect a significant reduction in disease mortality of 20%, and 4000 patients would be required to detect a more realistic 10% difference. A more recent study suggests that the number of patients needed to show a 30% reduction in disease recurrence would be less than 600 (2). A recent review of the existing literature suggested that patients with very low risk for disease recurrence (solitary tumor <1–1.5 cm, no invasion or lymph node involvement) did not benefit from radioiodine therapy (3). Patients with a high risk for disease recurrence [American Joint Committee on Cancer (AJCC) classification stages III and IV] clearly benefited from radioiodine therapy, and this was supported by a prospective, multicenter, nonrandomized trial (4). Patients in the low-risk group (stages I and II, 70–80% of patients with DTC) appear to have a reduction in disease recurrence in many but not all studies, and the effects of radioiodine on mortality are mixed (3). One problem with most studies that address the issue of recurrence is the definition of recurrence, which is not clearly stated in a majority of these studies. As technology advances, the definition of recurrence has evolved from symptomatic or palpable disease to radiographic evidence of disease, to identification of small, diseased lymph nodes on sensitive neck ultrasonography, to elevated serum thyroglobulin with or without TSH stimulation. The clinical relevance of this detected disease is also hotly debated.
