This study seeks to evaluate the role of radioiodine in the ablation of the remaining thyroid lobe, following a histopathological diagnosis of minimally invasive follicular carcinoma or papillary carcinoma of ≥1.5 cm size in patients undergoing hemithyroidectomy. There were 93 patients (69 females and 24 males) with an average age of 37.3±12.5 years (range, 16-70 years) and a mean follow-up duration of 46 months. Sixty-six of the patients had papillary cancer and remaining 27 had follicular thyroid cancer. The mean 24 h radioiodine neck uptake at the first visit was 17.2±7.3% (4.4-34%). In view of the large amount of thyroid tissue to be ablated, which may produce radiation induced thyroiditis, low doses of radioiodine (15-60 mCi) were administered to the patients. The patients were evaluated 6 months after radioiodine therapy with a 131I whole-body scan and 48 h radioiodine neck uptake, and a thyroglobulin assay after 4-6 weeks of levothyroxine withdrawal. The thyroid lobe was completely ablated in 53 patients (56.9%) after one dose of 131I and the remaining patients had partial thyroid ablation, with the mean radioiodine neck uptake being reduced to 3.1±2.4%. The mean first dose of 131I was 31.8±11.7 mCi; the estimated mean absorbed dose was 251.3±149.3 Gy (range, 120-790 Gy). Around 30% patients, in each of whom a remnant thyroid lobe was ablated with a single dose of radioiodine, received ≤200 Gy. The cumulative ablation rate was 92.1% after two doses of 131I. Only seven patients needed a third dose of 131I. In our cohort, 15 patients (16.1%) complained of throat discomfort and neck pain. All of them were managed with mild analgesics except three patients who needed additional oral prednisolone for 7-10 days to overcome neck oedema. We conclude that, although completion thyroidectomy remains the standard treatment after hemithyroidectomy in cases of differentiated thyroid cancer, radioiodine ablation of an intact thyroid lobe is possible and it can be achieved with much smaller doses of radioiodine than previously believed. Lobar ablation is an attractive alternative to surgery for those who refuse to undergo completion thyroidectomy or had complications during initial surgery. However, the long-term outcome in this subset of patients remains to be determined.
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India
Address all correspondence to Dr C.S. Bal, Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India 110029. e-mail: firstname.lastname@example.org
Part of this work was presented at the 46th Annual Meeting of the Society of Nuclear Medicine, Los Angeles, California, USA, 6-10 June 1999.
Received 18 June 2002, in revised form 3 August 2002 and accepted 13 August 2002