Endocrine Abstracts

The Northern Cancer Network Guidelines produced in 1999 for the management of differentiated thyroid cancer (DTC) state that patients should undergo two challenge scans after total thyroidectomy and radioiodine ablation; 6 months and 18 months after ablation. Due to the significant morbidity associated with thyroid hormone withdrawal in preparation for challenge scans, the need for the second scan has been questioned in the presence of a negative first scan and undetectable serum thyroglobulin level under TSH stimulation. The aim of this study is to assess the need for the second challenge scan for patients with DTC.

A retrospective study was carried out involving data from 64 patients diagnosed with thyroid cancer who had radioiodine ablation in 1999 and 2000. The data were analysed with respect to the scan results,the TSH and thyroglobulin levels at the time of the scans and the disease progression.

A total of 22 patients of the study population had a negative first scan and undetectable serum thyroglobulin level, of which 18 had a negative second scan. In three patients, however, a second scan was not carried out. One patient had a positive second scan, however, this was found to

be an artefact and the patient had no evidence of disease recurrence. Excluding the three patients who did not have a second scan, 95 % of patients with a negative first challenge scan and undetectable serum thyroglobulin level had a negative second scan.

Despite being limited by the small sample size, the results of this study show that the second challenge scan is of doubtful value and hence the guidelines for the management of DTC should be reconsidered.