rmination of the dosage given for therapy(57.2). Berg et al report using a relatively similar protocol (absorbed doses of 100-120 Gy) and that 93% of their patients required replacement therapy after 1-5 years [57.1].
More recently two more studies have presented methods for more accurately delivering a specific radiation dose to the thyroid, and report curing up to 90% of patients, with low incidence of recurrence or hypothyroidism(57.3, 57.4). Franklyn and co-workers have recently analyzed their data on treatment of 813 hyperthyroid patients with radioactive iodide and corroborate many of the previously recognized factors involved in response. Lower dose (in this case 5 mCi), male gender, goiters of medium or large size and severe hyperthyroidism were factors that were associated with failure to cure after one treatment. They suggest using higher fixed initial doses of radioiodine for treating such patients (58.2), as do Leslie et al(58.4). Santos et al (58.4) compared fixed doses of 10 and 15mCi and found no difference in utcome at 12 months post treatment. These suggest a standard 10mCi dose, with the larger dose reserved for larger glands.
Planned thyroid partial or complete ablation-All attempts to induce euthyroidism by a calculated moderate dose protocol end up with some patients hypothyroid, and others with persistent hyperthyroidism requiring further treatment. At this time many physicians giving 131-I therapy make no attempt to achieve euthyroidism, and instead use a dose sufficient to largely destroy the thyroid, followed by T4 replacement therapy . For example, a dose is given that will result in 7-20 mCi retained at 24 hrs, which is intended to induce hypothyroidism, accepting that in some (or many) patients this will ablate the thyroid completely. They argue that this is realistic and preferable since it offers 1) near certainty of prompt control, 2) avoids any chance of persistent or recurrent disease, 3)there is no benefit in having residual thyroid tissue, and 4) hypothyroidism is inevitable in most patients given RAI.Probably many patients given this treatment do in fact have some residual thyroid tissue that is either heavily damaged or reduced in amount so that it can not produce normal amounts of hormone. So far there is no evidence, in adults, that this residual radiated tissue will develop malignant change.
There is no certainty at this time that one approach is better than the other. It may be worth remembering that over 50% of patients given calculated modereate dose therapy remain euthyroid after ten years and can easily be surveyed at yearly intervals for hypothyroidism. When giving large doses of 131-I it is prudent to calculate the rads delivered to the gland (as above), which can reach 40-50,000. Such large doses of radiation can cause clinically significant radiation thyroiditis, and occasionally damage surrounding structures. And lastly, a speculation.
Practitioners comment that the incidence of serious ophthalmopathy seems to be less that in former decades. Prompt diagnosis and therapy might contribute to such a change. Another factor could be the more common ablation of the thyroid during therapy for Graves disease, since this should over time reduce exposure of patient’s immune system to thyroid antigens.
Lithium with RAI therapy– Although rarely used, RAI combined with lithium is safe and more effective than RAI alone in the cure of hyperthyroidism due to Graves’ disease, probably because it it causes greater retention of RAI within the thyroid gland.. Bogazzi et al (58.21)reported a study combining lithium with RAI therapy. MMI treatment was withdrawn 5 days prior to treatment, Two hundred ninety-eight patients were treated with RAI plus lithium (900 mg/d for 12 d starting 5 days prior to 131-I treatment) and 353 with RAI alone. RAI dosage was 260mCi/g estimated thyroid weight, corrected for RAIU (done on lithium).. All patients receive prednisone 0.5mg/kg/day, beginning on day 7 after RAI, tapering over 2 months. Patients treated with RAI plus lithium had a higher cure rate (91.0%) 