Treatment of advanced differentiated thyroid carcinoma with high activity radioiodine therapy

This was a retrospective study to assess the efficacy and morbidity of high activity I therapy in patients with advanced differentiated thyroid carcinoma.

From 1975 to 2003, 38 patients with locally advanced or metastatic differentiated thyroid cancer (16 follicular, 20 papillary, one Hurthle cell, one insular) were treated with high activity radioiodine therapy (9 GBq) as the cancers had previously not responded to standard activities (5.5 GBq).

Cumulative total activities received ranged from 11.8 to 84.5 GBq (mean 29.4 GBq per patient). Staging at presentation showed pT4 and/or M1 disease in 27/38 of patients (71.1%). Moderate (grade 2) and poorly differentiated (grade 3) tumours were present in a total of 9/38 patients (23.7%). Outcomes were evaluated according to the results of I whole-body scans, serum thyroglobulin, radiological assessments and physical examination. Neither [18F]flurodeoxyglucose positron emission tomography (F-FDG PET) nor 99mTc sestamibi were available during this study. The mean duration of follow-up was 83 months. A complete response was observed in 7/38 patients (18.4%), progressive disease in 27/38 (71.1%) and stable disease in 4/38 (10.5%). The mean survival from initiation of high activity treatment was 36.6 months. For patients with lung disease the mean survival was 45 months, neck disease 38.9 months, bone disease 35 months and multiple sites was 30.9 months. Twelve patients died during follow-up (10 due to thyroid carcinoma). After high activity treatment, 9.7% of patients suffered grade 3 and 3.2% suffered grade 4 WHO haematological toxicity. Significant salivary gland morbidity was observed (30% dry mouth, 27% salivary swelling).

Repeated treatment with high activity (9 GBq) I in patients with advanced differentiated thyroid carcinoma appears to be of no apparent benefit and may lead to late morbidity.